This section of the guide attempts the impossible—to explain in relatively few pages how a house is constructed. Though this may seem complex at first glance, the reader will find that he or she is familiar with a great deal of information. Substantial reliance has been placed on the Minimum Property Standards established by the U.S. Department of Housing and Urban Development (MPS).
According to the MPS, the objective of the excavation is to provide a safe and adequate support for footings and foundations. Adequate clearance is needed to ensure protection against damage by decay or insect attack. Good excavation also provides drainage for and access to basement-less space.
The process usually involves several steps. First, the location of the house is staked out by the builder or surveyor and the topsoil is removed to a point where it's stored during the construction process and re-spread as the final step in the finish grading. Then the main hole is dug—first, usually with the help of a power shovel and then by hand to a depth 6 to 10 inches below the floor level. Finally, trenches are dug for the footings and service pipes, drains, dry wells and septic tanks.
The MPS specifies that excavations for footings and foundation walls should extend at least 6 inches into natural, undisturbed soil to pro vide adequate bearing except where bearing is on a stable rock formation and below the prevailing frost line.
Footings and Foundation Walls
The objective of the footing, according to the MPS, is to provide support for the dwelling without excessive differential or overall settlement or movement. The footing is the perimetric base of concrete that's laid by pouring the concrete into wooden forms set at a level below the frost line and on undisturbed earth. All substructures will settle to a certain extent unless they are located on solid bedrock. Also, excess shifting and settlement will cause cracks and leaks in the foundation wall and uneven floors in the house. Thus, local building codes specify the required depth for each region based on the local frost-line depth.
Because the foundation must provide safe and adequate support for all vertical and lateral design loads, all foundation walls are poured or laid on top of the footings. Block walls must be properly laid and well mortared, then filled with concrete and made watertight with cement plaster or other waterproofing compounds. Cinder blocks are porous and thus are inferior to cement blocks for a solid foundation. Brick and tile, although good foundation materials, are costly and require substantial skill for proper laying, as does stone, which once was very popular in the Northeast. Figure 5-1 illustrates the footing and foundation of a house.
The three basic forms of foundations are basements, crawl spaces and slab-on-ground. With the exception of those houses being constructed in the northern portions of the country, fewer and fewer houses are being built with basements. and , where basements are built, there is an increasing trend to gain additional living space by finishing portions into family rooms, utility areas, baths and lavatories, workrooms, kitchens and even bedrooms. In the event that the house has a basement, the height between the basement floor, which is constructed similarly to a slab, and the bottom of the joists usually is 7 ½ to 8 feet.
For basementless houses, the finish grade is a major factor in the choice between slab-on-ground or crawl space as a foundation. For slab- on-ground construction, the finished ground grade must fall sharply away from the house to prevent flooding. Slabs are constructed by first building footings for support, although some slabs, known as “floating slabs,” are built without them. The excavation then is covered with gravel and a vapor barrier and insulation is installed around the edge. Figure 5.2 illustrates a structural slab on grade.
Crawl spaces, which provide flooding protection and also provide a convenient place to run heating ducts, plumbing pipes and wires that must be accessible for repairs, are constructed similarly to basements except that the distance from the floor to the joists is 3 to 4 feet. The floor can be concrete, as in a basement, or it can be dirt, often covered with a vapor barrier. In northern regions, crawl spaces must be insulated or heated to prevent pipes from freezing and floors from becoming cold.
A Wet or Damp Basement
Dampness, of course, is the main problem with basements, for it damages wall and floor coverings, furniture, clothing and other possessions. It also poses a health hazard—especially when the basement is used for sleeping. Some of the causes of basement dampness that can be thwarted by the careful builder are poor foundation wall construction, excess ground water not properly carried away by ground tiles, poorly fitted windows or hatch, a poorly vented clothes dryer, gutters and downspouts spilling water too near the foundation wall and a rising water table in the ground.
A basement that's wet or damp only part of the year usually can be detected any time by careful inspection. All the walls should be checked for a powder-white mineral deposit a few inches off the floor. Only the most diligent cleaning will remove all these deposits after a basement has been flooded.
Stains along the lower edge of the walls and columns and on the furnace and hot-water heater are indications of excessive dampness, as is mil dew odor.
The causes of a wet and damp basement are numerous. Some are easily corrected and others are almost impossible to correct. In areas where the soil drainage is poor or the water table is near the surface of the ground, well-constructed footing and foundation drains are needed to maintain a dry basement. They should be installed when the house is constructed because this is expensive to do afterward. The same is true of a vapor barrier under the basement floor, which is very easy to put down during construction but impossible afterward.
Cracks in the floor and walls may be patched with various widely marketed compounds. A more drastic step is to dig down and repair the wall from the outside.
What first appears to be a major water problem might be traced to a leak in a window or the hatch door. A simple caulking job will stop the water from coming in. Water will leak in through a window at the bottom of a well that does not drain properly in a heavy rainstorm. Extending the drain line or deepening the dry well stops this problem.
The earth around the house should slope away from the foundation wall so ground water will not collect along the edge of the foundation. If there is an edge of the roof line without a gutter, water may be running off and collecting next to the foundation wall. The water that's collected by the gutter and flows into the leaders must be diverted away from the foundation wall. The leader should run into a sewer drain, dry well or splash pan—in that order of preference.
Dampness and mildew also may be caused by moisture condensing on the walls, ceiling and pipes. Proper ventilation eliminates this problem.
Main Bearing Beam and Columns
Because most houses are too large for the floor joists to be spanned from one foundation wall to the opposite foundation wall, one or more bearing beams resting on columns or piers are used to support the floor joists. If only one beam is required, it runs roughly down the center of the basement or crawl space.
Steel beams, because of their great strength, can be used to span longer distances than wood beams of the same size. Steel beams, however, are subject to fire damage from relatively low heat. A steel beam will lose some of its strength at 500 degrees and at 1,000 degrees will buckle under a normal load. Beams that are covered with metal lath and plaster, on the other hand, will maintain their strength under much higher temperatures for long periods of time.
Wood beams, although not so strong as steel, often are used and are quite satisfactory. When a solid beam is used, it generally is 6 by 8 inches to 10 by 10 inches. Plank beams consist of several 2-inch by 6-inch to 2- inch by 10-inch planks placed side by side on end to achieve the desired thickness.
Most beams are supported by wood posts, brick or block piers or metal Lally columns that are concrete-filled steel cylinders. The post, pier or column must rest on a footing, which should be at least 2 feet square and 1 foot thick. If brick and block piers are used, they should be at least 12 inches square but preferably 16 inches square. If wood posts are used, they should be set on a platform several inches off the floor so that any water on the floor from leaks will not rot them. Steel columns require caps and base plates.
Nine out of ten houses in this country are wood-frame constructions. Many of them are covered with wood siding; others may be covered with wood shingles, composition shingles or siding, brick veneer or stucco. Regardless of the type of exterior covering, these houses fall in the general classification of wood-frame construction. There are, however, three different types of wood-frame construction, as shown in Figure 5.3: plat form, balloon, and plank and beam.
In platform-frame construction, the subfloor extends to the outside edges of the building and provides a platform on which exterior walls and interior partitions are erected. Platform construction is the type of framing most generally used for one-story houses. It also is used alone or in combination with balloon construction for two-story structures. Thus, because of the platform frame’s wide use, building techniques in some parts of the country have been developed almost exclusively around the platform system.
A platform-constructed house is easier to erect than other houses be cause, at each floor level, a flat surface is provided on which to work. Moreover, the platform system also is easily adapted to various methods of prefabrication. With a platform framing system, it's common practice to assemble the wall framing on the floor and then tilt the entire unit into place.
With balloon-frame construction, both studs and first-floor joists rest on the anchored sill. The second-floor joists bear on a 1-inch by 4-inch rib bon strip that has been let into the inside edges of the studs.
Balloon framing is a preferred type of construction for two-story buildings where the exterior covering is of brick or stone veneer because there is less likelihood of movement between the wood framing and the masonry veneer. Where exterior walls are of solid masonry, balloon framing also is desirable for interior bearing partitions because it eliminates any variations in settlement that may occur between exterior wall and interior supports.
In the plank-and-beam method of framing, beams of adequate size are spaced up to 8 feet apart and are covered with 2-inch planks that serve as the base for finish flooring or roof covering. The ends of the beams are supported on posts and the covering for exterior walls is attached to supplementary members set between the posts. Details for this method of construction are provided in Wood Construction Data No. 4 of the series published by the National Lumber Manufacturers Association.
One advantage of plank-and-beam framing is that it lends itself to the construction of contemporary houses where the planks and beams are used as exposed, finished materials.
EXTERIOR FRAME WALLS
Exterior wall framing should be strong and stiff enough to support the vertical loads from floors and roof. Moreover, the walls should be able to resist the lateral loads resulting from winds and , in some areas, from earthquakes. Thus, the top plates should be doubled and overlapped at the wall-and-bearing-partition intersection to tie the building together into a strong unit.
Studs, which in exterior walls are placed with the wide faces perpendicular to the direction of the wall, should be at least 2 by 4 inches for one-story and two-story buildings. In three-story buildings, studs in the bottom story should be at least 2 by 6 inches. In one-story buildings, studs may be spaced 24 inches, on center, unless otherwise limited by the wall covering, while in multistory buildings spacing shouldn't exceed 16 inches on center. In all cases, an arrangement of multiple studs is used at the corners to provide for ready attachment of exterior and interior surface materials.
Where doors or windows are to be located, provision must be made in the framing to carry the vertical load across the opening. This provision is made by a header of adequate size, the ends of which may be sup ported either on studs or by framing anchors when the span or opening does not exceed 3 feet in width.
If the builder chooses, a continuous header consisting of 2-inch members set on edge may be used instead of a double top plate. If a continuous header is used, the depth of the members must be the same as that required to span the largest opening and the joints in individual members should be staggered at least three stud spaces and shouldn't occur over openings. Moreover, the members should be toe-nailed to studs and corners; intersections, with bearing partitions, should be lapped or tied with metal straps. Studs in gable ends should rest on wall plates with top notches to fit the end rafter to which they are nailed.
Defective House Framing
When a house is a few years old, signs of defective framing can be detected visually. One sign is bulging exterior walls, which can best be seen by standing at each corner of the house and looking along the wall. Another method is to make a plumb line out of a key and string and hold it against the wall. If the ridge line sass in the middle, trouble is developing.
Windowsills that aren't level are a sign of settling, defective framing or original sloppy carpentry. A careful house inspection should include the opening and closing of every window. Sticking windows may indicate settling or defective framing.
A sure sign of trouble is a large crack developing on the outside of the house between the chimney and the exterior wall. Other tip offs to defective framing are cracks running outward at an angle from the upper corners of window and door frames.
Sagging and sloping floors may be detected visually or by putting a marble on the floor and watching to see if it rolls away. This may be a sign of defective framing.
Cracks in the walls other than those discussed previously should be a cause of concern but in themselves aren't conclusive evidence of framing problems. All houses settle unless they are built on solid rock. Rare is the house that does not develop some wall and ceiling cracks. An owner should become concerned when these cracks are accompanied by some of the other signs of defective framing.
Exterior walls should be braced by a suitable sheathing applied horizon tally or, preferably, diagonally to the framing. The diagonal method of placing sheathing is preferable to the horizontal because additional strength and stiffness may be provided by 1-inch by 4-inch members set into the outside face of the studs at an angle of 45 degrees and nailed to the top and bottom plates and studs. Moreover, where wood sheathing boards are applied diagonally, let-in braces aren't necessary. In either case, sheathing should be nailed to sills, headers, studs, plates or continuous headers and to gable end rafters.
Wood sheathing is preferred by many builders because it provides a solid nailing base for applying exterior siding and finish. It usually is available in square-edge, shiplap or tongue-and-groove patterns. and when it's employed, joints should be made on studs unless end-matched boards are used, in which case each board should bear on at least two studs. Plywood, however, also makes an excellent sheathing material that can be nailed, stapled or glued to the frame. Other materials used as sheathing include fiberboard and specially fabricated gypsum panels that often have the sheathing paper and exterior finish incorporated into them.
Weather-tight walls are provided by covering the sheathing on the outside with sheathing paper that may be either asphalt-saturated felt weighing not less than 15 pounds per 108 square feet or any other impregnated pa per with equivalent water-repellent properties but which will not act as a vapor barrier. Starting at the bottom of the wall, the sheathing paper should be applied by lapping it 4 inches at horizontal joints and 6 inches at vertical joints. Then, strips of sheathing paper about 6 inches wide should be installed behind all exterior trim and around all openings.
Wherever joints occur in which dissimilar materials come together or wherever there is a possibility of leakage because of the type of construction, it usually is necessary to insert flashing—sheets or membranes of waterproof materials—to repel the water.
Although flashing may be composed of impregnated felt or of combinations of felt and metal, it generally is composed of one of the following metals: copper, zinc, lead, leaded copper, tin, galvanized iron or steel, tin-plated steel, soft iron and copper-bearing or alloy steel. Of these, the pure metals are the best. and of the pure metals, copper, lead, zinc and leaded copper are the most commonly used and the most effective be cause they corrode and deteriorate the least on exposure to the weather. Coated sheets such as galvanized iron and tin-plated steel are satisfactory as long as the coating is unbroken. Once the coating is broken, however, corrosion may be accelerated by the electrolytic action set up between dissimilar metals.
No matter what metal is employed, the installation of flashing is practically identical. Thus, the following discussion, although based on copper (the metal most widely employed for flashing), applies to all the other metals that can be used.
When using metal exposed to changes in temperature found on building exteriors, the first point to remember is that metals have fairly high coefficients of thermal expansion and must be free to move with changes in temperature. If they are confined, the stresses set up in trying to change dimensions eventually cause fatigue cracks. Short, narrow strips, less than 10 to 12 inches wide, can be fastened along both edges without much danger; wider sheets, however, must not be confined along two opposite edges but must be free to move.
The second point to remember is that flashing must be installed in such a way that water is shed over any unsealed joints in it, i.e., joints must be so made that water could work through them only against the force of gravity. Furthermore, it must be impossible for driving winds to force water through. Thus, it usually is necessary that the joint either pro vide a tortuous path in which the driving force of the wind is dissipated or that the laps in the joint are long enough that water can't possibly be driven through.
Copper flashing generally is 16-ounce “roofing temper” (R.T.), a soft and pliable material weighing 16 ounces per square foot. Heavier copper is required for heavy-duty flashing such as that around certain kinds of tile roofs, whereas lighter copper (not less than 14-ounce) can be used in relatively protected points.
Once framing, sheathing and flashing are dealt with, the matter of finishes for the exterior must be considered. Many types of siding and other exterior coverings are applied over wood framing. Often a house may have more than one type of siding on it. Numerous patterns of wood siding are available. The names of different types, varying with the locality, include bevel, bungalow, colonial, rustic, shiplap and drop siding. Figure 5.4 shows a few types of wood siding.
If bevel siding or square-inch boards are used, they should be applied horizontally and lapped 1 inch with nails driven just above the lap to permit possible movement because of changes in moisture conditions. More over, the boards should be spaced so that the bottoms of the pieces coincide with the top of the trim over the door and window openings—an arrangement requiring careful planning by the carpenter before starting to apply the siding. Finally, when using bevel siding or square-inch boards, it's a good practice to apply a liberal coating of water repellent to the end surfaces. No matter what the siding or exterior trim, it should be installed with corrosion-resistant nails, usually of galvanized steel or aluminum. Where wood sheathing is used, siding may be nailed at 24-inch intervals. Where other types of sheathing are used, the nails should be driven through the sheathing into the studs at each bearing. The length of the nails will vary with the thickness of the siding and the types of the sheathing.
Where shingles are installed in double courses (double layers), the butt of the exposed shingle should extend about 1/4 inch below the under- course or layer to produce a shadow line. The under-course should be attached to the sheathing with nails or staples and the outer-course attached with small headed nails driven approximately 2 inches above the butts and 3/4 of an inch from the edges.
In all cases, however, shingles should be nailed with corrosion- resistant nails of sufficient length to penetrate the sheathing, using two nails for shingles up to 8 inches wide and three nails for wider shingles. When shingles are installed in a single course or layer, the nails should be driven approximately 1 inch above the butt line of the following course.
Finally, when siding other than wood sheathing is used, 1-inch by 3- inch horizontal nailing strips must be applied over the sheathing spaced to correspond with the weather exposure of the shingles. Figure 5.5 illustrates two other types of siding: stucco and masonry veneer.
Stucco still is popular in dry climates where it can be applied directly to the surface of a solid masonry wall. The application of stucco to a wood frame wall, however, generally is more involved than the application of other finishes. Thus, the high cost of labor for its application has reduced its popularity in the northern parts of the country.
When stucco, which is a type of plaster that can be variously patterned or colored, is used, its application involves the following steps. First, wood firing strips are nailed to the sheathing through the building paper. Then metal lathing is stretched onto the firing strips. Finally, the stucco is troweled onto the lathing.
A masonry veneer wall is really a frame wall with some variety of masonry siding, most commonly clay bricks, concrete bricks, split blocks or stone. In houses with masonry veneer walls, all of the structural functions of the walls are performed by the framing and not by the one-unit- thick masonry that's tied to the frame wall with rustproof metal ties spaced one tie for each 2 square feet of wall. When the walls are constructed, 3/4 inch to 1 inch of air space is left between the masonry and the sheathing and weep holes are installed at the base to let moisture escape.
A variety of other types of siding materials are available. These include aluminum, stone, hardboard, gypsum board, fiberglass and metals. Each of these requires special techniques for proper installation. Instructions are provided by the manufacturers and should be followed carefully.
SOLID MASONRY WALLS
Solid masonry walls, if well constructed, are very durable and easily maintained. They should be insulated, however, and they do require a larger foundation than a wood frame wall. Such walls can be either one or two units thick. Single-unit-thick walls are most commonly made of 8- inch concrete.
While solid multiple-unit masonry walls were, until recently, the most common type of masonry wall, they now are mainly used only where required by local building codes. Where they are used, these walls are constructed either of two layers of brick, tile or cement block or of a combination of materials, with the higher grade on the outside and the cheaper unit as the backup. In the latter case, masonry headers (bricks laid across two thicknesses of walls) or metal ties are used to tie the face units to the backup units.
HOLLOW MASONRY WALLS
In the case of hollow masonry walls, a cavity masonry wall is built of two units that are separated into an inside and outside wall by 2 to 4 inches of air space and bonded together with metal ties or joint reinforcement. The exterior wythe (thickness) is usually 4 inches and the interior wythe, 4 to 8 inches.
These cavity walls are used mainly in northern sections of the country for protection against severe outside temperatures and storms. They provide added protection from the elements when insulation is installed in the cavity and eliminate the need for furring on the inside wall because moisture penetration is almost impossible if cavity walls are properly constructed with flashing and weep holes (holes at the bottom to let any moisture escape).
Masonry bonded walls are similar to cavity walls except that the two wythes are joined by masonry header courses instead of by metal ties. Al though they are economical to construct, their insulation qualities are inferior to those of cavity walls and they are, therefore, used mainly in the Southwest.
CLAY BRICK and TILE INSTALLATION
The primary factor in good brick and tile construction is proper installation. The major source of problems is partially filled mortar joints that will substantially reduce the strength of the wall and contribute to rapid disintegration and cracking. Water then penetrates the wall and expands during the freezing cycle further cracking the mortar. Figure 5.6 illustrates the terms and the methods in brick construction.
Storage and Preparation of Materials on Site
Bricks and tiles should be stored off the ground and covered. High- suction brick when laid dried absorbs the water from the mortar; there fore, the brick must be thoroughly soaked with water prior to installation. The brick or tile then is left to surface dry because surface water, by causing floating, will interfere with the bond between the brick or tile and the mortar.
Laying the Brick or Tile
This process begins by locating the corner and laying out the first layer of brick or tile to determine how much cutting or extending will be needed for an exact fit. A full, thick bed of mortar is spread for the first course. Several units are laid and then aligned with a level. After the first course is laid, the corners are built up. A line is stretched from corner to corner for each course and the top outside edge of each unit is laid to this line. Head joints are completely filled with mortar on the end of the brick be fore placement. When the brick is pushed into place, mortar squeezes out of the sides and top, indicating that the head joint is completely filled. Al ternate ways of filling the head joint are to place a trowel of mortar on the end of the brick already in place or to place a full trowel of mortar on the wall and squeeze the brick into place, forcing the mortar up into the head joint.
There are two basic types of mortar joints—troweled joints and tooled joints. With troweled joints, after the brick or tile is laid in place, the excess mortar squeezes out of the joint. If the mortar is simply removed with a trowel and no further finishing is done, it's a struck joint. If it's struck off parallel to the unit surface, it's a flush or plain cut joint. If it's struck on an angle with some of the joint removed, it's a struck joint. If some of the top of the joint is removed, it's a weathered joint. For most residential purposes, the weathered joint is preferred because it sheds water.
A tooled joint is a better joint that's tooled with a special tool that compresses and shapes the mortar in the joint. Common types of tooled joints are rodded joints, V-shaped joints and beaded joints.
When more than one unit thick of brick or tile is used in the wall, the back of the face brick or tile may be covered with mortar. This parging will substantially increase the waterproofing of the wall. Basement walls usually are parged.
By inserting short lengths of sash cord through the mortar at the bottom, a weep hole is made through which any water that gets inside a double-unit wall may run out.
After the wall is completely laid and let stand for 48 hours, its surface is cleaned from top to bottom with soap and water. Stains are removed with hydrochloric acid after the wall is seven days old.
CONCRETE BRICK and BLOCK INSTALLATION
A good, solid concrete brick or block wall depends on good workman ship and proper installation. The joints must be well made and the unit carefully laid. The space between the bricks should be completely filled. Partially filled joints make a weak, leaky wall that's subject to cracking easily.
Storage and Preparation of Material on Site
The amount of moisture in concrete masonry is controlled to meet building specifications. Steps often taken to keep the units dry are putting them on planks to keep them off the ground and covering them with a waterproof cover. Concrete units are laid dry.
Laying the Brick or Blocks
The corner is located and the first layer of brick or block is laid out to determine if a cutting will be needed or if the desired wall length can be obtained by adjusting the size of the joints.
A full thick bed of mortar is spread for the first course and furrowed with a trowel to ensure that there is plenty of mortar along the bottom edge of the face shells of the block. Blocks are laid with their thicker side up. Several units are laid and then aligned with a level. After the first course is laid, the corners are built up. A line is stretched from corner to corner for each course and the top outside edge of each unit is laid to this line. The balance of the laying process is generally the same as for clay brick and tile.
INSULATION and WEATHERPROOFING
Organic substances such as eelgrass, animal hair and sawdust were the first materials used in insulation. Production of man-made insulation material began in 1840 in Wales and in the United States in 1875, when “mineral wool” (inorganic fibrous insulation) was derived from iron slag. Pneumatic installation and blanket-and-bat production started in the 1920s followed by glass-fiber insulation production in the mid-1930s.
Prior to World War II, however, many houses were constructed with little or no insulation because their heavy building materials and tight- fitting window and door sashes provided them with sufficient weather resistance. Newer houses, constructed of lighter materials and with less precise workmanship, require insulation to keep the heat and cold from penetrating.
Residential insulation, which is reasonable and easy to install as part of the initial construction, falls into the following five categories: loose, blankets and bats, foil, sprayed on and wallboard.
The most popular loose materials are rock wool, glass wool, slag wool, perlite, vermiculite, wood fiber, paper, cotton fiber paper and macerated paper. All of these products, which should be bug-proofed and fire-proofed before installation, may be blown or poured into the hollow spaces between the studs on the exterior walls and above the ceiling or be low the roof rafters. The major disadvantage, however, is that they tend to settle, thus eventually leaving uninsulated spaces.
Blankets and bats usually are made of the same material as wall board, loosely felted, glued between two sheets of treated paper or foil and quilted. When installed, they are stapled, clipped or nailed with lathing between the studs and under the rafters or over the ceiling. Insulation under the rafters is called “cap insulation,” while insulation in all the walls between the heated and the unheated portions of the house is “full insulation.”
Sprayed-on insulation is a hot, viscous mixture that's sprayed onto the inside of the sheathing. When it cools and solidifies, it becomes a porous layer 1 to 2 inches thick. Foil, usually aluminum that's several thousandths of an inch thick, is another type of insulation that can be installed in up to four layers. It is especially effective in keeping heat out.
Wallboard insulation, which is used successfully under siding and roofs, is made of a variety of synthetic materials or wood and vegetable fibers, which are mechanically separated and then recombined by matting or felting to form many small air cells. The board is formed by putting the material under pressure. The more pressure used, the stronger and more rigid the board but the less effective its insulating qualities. There fore, only moderate pressure should be used, thus causing the boards to be much softer than regular wood.
The two primary benefits of insulation are fuel economy and occupant comfort. Its secondary benefits are the reduction of sound transmission and the reduction of the danger of fire spreading. Insulation keeps the heat inside when it's cold outside and the heat out when it's hot out side. Therefore, good insulation is important in most climates.
When examining the economic benefits of insulation, the first question that arises is, how much can be saved by the proper insulation of a house? The answer depends on many factors but mainly on how weather proof the windows and doors have been made and on the quality both of the ceiling insulation and ventilation and of the wall insulation. The calculation of the heat losses and gains in terms of insulation is a subject best left to heating and cooling experts. Local electric companies, how ever, will supply complete information on how the losses and gains can be calculated.
Here are some rules of thumb for heating and cooling savings that can be obtained by adding various types of weatherproofing and insulation to a frame, one-story building:
The total difference between fuel costs for an uninsulated house and for an otherwise identical one with storm windows and doors and good insulation in the walls and ceiling can be 50 % .
The standard measurement for the effectiveness of insulation is its “R” value (resistance to heat flow). The higher the “R” value, the better the insulation. Thus, most brand-name insulation products are marked with their “R” value.
Over-ceiling or under-roof insulation should have an “R” rating from R-13 in mild climates where there is no air-conditioning and gas or oil heat to R-24 or better in colder climates or hot climates or where there is electric heat or air-conditioning.
Exterior wall insulation requires an R-11 rating for hot or cold climates or electric heat or air-conditioning, down to R-8 for mild climates, no air-conditioning and gas and oil heat.
Floor insulation, if a house is built over a crawl area, should be at least R-9 and preferably R-13. When the house is built on a slab, only edge floor insulation is required. and when the house is built over a basement, no floor insulation is needed at all.
When examining the occupant comfort benefits of insulation, the first to consider is reduction of the “cold wall” effect. The human body feels uncomfortable when it's losing heat too fast. and , even if a room itself feels warm, body heat will radiate to a nearby cold surface (wall, floor, ceiling) and produce a chilled feeling. In the summer, reverse conditions are in effect when excessively warm surfaces make it difficult for the body to maintain its normal temperature.
To compensate for the discomfort produced by heat radiation, most people will set the thermostat higher in the winter and lower in the summer, thereby increasing the fuel cost. But insulation helps to make a house comfortable without increased fuel costs because it helps make more uniform room-to-room and floor-to-ceiling air-temperature differences. Moreover, it reduces drafts from convection currents that are generated by interior surface-air temperature differences.
Figure 5.7 illustrates the recommended insulation and ventilation for a house.
According to the MPS, a dwelling ideally should provide natural ventilation in areas such as attics and basementless spaces to minimize decay and deterioration of the house and to reduce attic heat in the summer. Thus, the MPS makes the following recommendations:
1. Eight-mesh-per-inch screening should be used to cover all exterior openings.
2. At least four foundation-wall ventilators should be provided in basementless spaces or crawl spaces unless one side of such space is completely open to the basement.
3. Cross ventilation should be provided in an attic and in spaces between roofs and top-floor ceilings by venting. All openings should be designed to prevent the entrance of rain or snow.
INTERIOR WALLS and CEILINGS
Interior Masonry Walls
Interior masonry walls can be classified as either load bearing or non-load bearing. According to the MPS, the load-bearing walls should be 6 inches thick when supporting not more than one floor and 8 inches thick when supporting more than one floor. Nonbearing partitions should be 3 inches thick and all masonry should be supported on masonry, concrete or steel. Wood framing shouldn't be used for support and intersecting masonry walls should be bonded or anchored together.
Interior Wall Framing
An interior wall or partition is framed in generally the same way as an exterior wall. First, a shoe or sole plate is nailed to the subflooring. Then, studs are nailed to this plate either 2 by 4 inches for bearing walls or 2 by 3 inches for nonbearing walls. and finally, the top of the stud is nailed to a ceiling plate or cap.
Framing around door openings also is erected in the same manner as in exterior walls. Openings under 36 inches may be single- or double- framed (one or two studs) and jamb studs should extend in one piece from header to sole plate, according to the MPS.
The bottom sides of the joists for the floor above act as the framing for the ceiling below. Finishes are applied to the ceiling joists similarly to the way in which they are attached to the wall studs. Usually, ceiling joists should be a maximum of 16 inches on center.
INTERIOR WALL and CEILING FINISHES
An MPS objective is to secure an interior wall and ceiling finish that will provide a suitable base for decorative finish, a waterproof finish in spaces subject to moisture and reasonable durability and economy of maintenance. The materials now most commonly used to fulfill this threefold objective include plaster, gypsum, plywood, hardboard, fiberboard, ceramic tile and wood paneling.
Plaster walls are constructed by applying up to three coats of plaster over either metal lath, wire lath, wire fabric, gypsum lath, wood lath or fiber board lath that has been attached to the studs or furring strips. Over metal lath, wire lath and wire fabric, the plaster usually is applied in three coats. The first two are called the scratch coat and the brown coat, respectively. Together they are about 1/8 inch thick. The final white coat is a maximum of 1/16 inch thick. Over gypsum lath, wood lath, fiberboard lath or masonry, the plaster can be applied as previously described or in two coats to a minimum thickness of 1/2 inch.
A well-constructed plaster wall provides a high degree of sound- proofing. Its main disadvantages, however, are high cost and susceptibility to cracking.
Loose or Defective Interior Plastering
As long as cracked plaster is tight to the wall, it may be sufficient to just patch and redecorate a crack.
Bulging plaster on the ceiling is dangerous and should be repaired. When this is suspected, the defect often can be detected by pressing a broom handle against the ceiling and feeling if there is any give in the plaster.
Gypsum drywalls are constructed by nailing, gluing or screwing sheets of gypsum boards directly to the studs or masonry or to furring strips attached to the masonry wall.
As the MPS prescribes, “When single 1/8 inch thick sheets of gypsum board are used they should be nailed to studs 16 inches o.c., i.e., on center. When 1/2 inch and 1/8 inch thick sheets are used, the studs may be 24 inches o.c. When two layers of 1/8 inch thick or thicker gypsum board are used, the stud may be 24 inches o.c.” Moreover, when constructing gyp sum drywalls, all exterior corners should be protected with metal corner beads, angles or wood molding to prevent damage and all joints in wall board surfaces to be painted or wallpapered should be taped and cemented.
Gypsum drywalls eliminate the time wasted by the drying out period between coats applied to plaster walls. A disadvantage of gypsum dry- walls, however, is the possibility that nails may pop out if there is an improper moisture content in the studs.
Plywood can be nailed or fastened directly to the studs. One-quarter-inch plywood requires studs 24 inches on center. Plywood of any thickness can be nailed over gypsum board.
Like plywood, hardboard is nailed or fastened directly to the studs or fur ring strips. As the MPS prescribes, “When applied alone it should be a minimum of 1/4 inch thick with the studs 16 inches o.c.”
Also like plywood, fiberboard is nailed or fastened directly to the studs or furring strips. According to the MPS “When applied alone it should have a minimum of 1/2 inch thickness with studs 16 inches o.c. and 3/4 inch thickness with studs 24 inches o.c.” Although plywood, hardboard and fiberboard vary in cost according to thickness and quality, they often pro vide less expensive interior wall finishes than plaster or gypsum.
Ceramic Wall Tile—Cement-Plaster Method
When ceramic wall tile is applied by the cement-plaster method (also known as a mud job), a plaster wall is constructed by installing lath over water-resistant sheathing paper attached to the studs that should be firmly blocked to support the heavy weight of the tile. Next, two coats of plaster are applied to the lath. The first coat is the scratch coat that forms the base and the second is the mortar coat into which the tiles are embedded. The scratch coat is allowed to thoroughly harden and then is re-dampened. Next, the tiles are set into the freshly applied mortar coat by either “floating” or “buttering.” “Floating” is placing the tile in the mortar with small, twisting motions, while “buttering” is spreading the mortar on each individual tile as butter is spread on bread. After the tiles are floated or buttered, the joints between the tiles are filled with a thin grout of white or gray portland cement and water. Finally, all traces of cement on the surface are wiped off.
Ceramic and Plastic Tile Wall—Adhesive Method
When a ceramic or plastic tile wall is used as an interior finish, first a wall of plaster, gypsum or other wallboard is constructed as previously de scribed. Then, the entire surface is sealed with a water-resistant sealer. Next, the tile adhesive is applied to the entire surface with a notched spreader blade. Then the tile is set by the floating method. The buttering method of setting this tile shouldn't be used for it does not make a good bond. Finally, the wall is finished in the same manner as in the plaster method.
Cracked, Loose or Leaking Tiles
The principal area where tile problems occur is around the tub, especially when there is a shower that splashes water on the tile wall. Defective grout will permit the water to seep behind the tile and loosen the glue. New types of waterproof adhesives help eliminate this. Tiles set in plaster also are less likely to present problems.
This is an area where initial good workmanship will produce lasting, trouble-free results, while shoddy work soon will have to be redone. Often when repairs are undertaken, it may be necessary to replace the wallboard that has become damaged by the moisture. Special waterproof wall- boards now have been developed to cut down this problem.
When wood paneling is used as an interior finish, the MPS suggests that the “wood panel… be thoroughly seasoned and suitable for its intended use and applied over No. 15 asphalt-saturated felt or vapor barrier when application is direct to exterior wall framing or blocking” and that its maximum width be 12 inches, its minimum thickness 1/2 inch and the maximum spacing of supports 24 inches on center.
The objective, according to the MPS, of a well-planned stairway is to pro vide safe ascent and descent and a design and arrangement of stairs that assures adequate headroom and space for moving furniture and equipment.
The major part of a staircase running from one floor to the next or from a floor to a landing is called a flight. Important components of a staircase are the stringers (also called carriages or horses) that run at an angle from one floor or landing to the adjoining floor or landing and that support the horizontal member or top of the stair called a tread and the vertical front of the stair called the riser. The approximately triangular-shaped threads on a curve are winders. and the tip of the tread that extends beyond the riser is the nose. The width of the rise is called the run. Often under the nose is a piece of cove molding.
The handrail can be attached to the wall with brackets or supported by posts called balusters. The end of the handrail that curves parallel to the floor is the easing and the top of the bottom baluster is a newel.
A complicated staircase always must be carefully planned. According to the FHA, a simple check for adequate design of the stairs includes the following features: headroom, width clear of handrail, run, rise, winders, landings, handrail and railings.
Depending on the custom of the area and the facilities and skills of the builder, stairs are built in place or they are built as a unit in the shop or mill and delivered preassembled to the site to be set in place. Because the construction of a spiral, dog-leg stairway requires special skills, most stairs built today are straight.
A built-in-place stair is made first by cutting the carriages and setting them in place with the top nailed to the header of the upper floor and the bottom resting on the lower floor. The treads and risers, which are tongued and grooved to fit together, are nailed to the stringers and the cove molding is nailed under the nose of the tread. Then, if a wall stringer is used, it's fitted into place.
Balusters can be attached to the treads by nailing (which is the poorest method), by being inserted into drilled holes in the rail and tread (a more satisfactory method than nailing but one that carries the risk of the rail tending to loosen in time and turn) or by dovetailing the lower end of each baluster into the tread and fitting the upper end into holes bored into the lower side of the railing.
The rails are attached to the walls of enclosed stairs with wall brackets, which shouldn't be more than 10 feet apart, and then securely screwed or lag-bolted to the studs or blocking. They shouldn't , however, be screwed into the lath.
Figure 5.8 illustrates wood stair construction.
The first feature that must be considered with interior stairs is headroom, which should be continuous and clear, measured vertically from the front edge of the nosing to a line parallel with the stair pitch. For main stairs, there should be a minimum of 6 feet, 8 inches of headroom and for basement and service stairs, a minimum of 6 feet, 4 inches. On interior stairs, the width clear of the handrail should be at least 2 feet, 8 inches for main stairs and at least 2 feet, 6 inches for basement or service stairs.
Main stairs with either a closed or open riser, as well as basement stairs with a closed riser, should have a run of at least 9 inches plus a 1 1/8-inch nosing. Basement stairs with an open riser require a run of at least 9 inches plus a 1/2-inch nosing.
The maximum riser height condoned by the FHA for interior stairs is 8¼ inches. The winders should run at a point 18 inches from the converging end and should be no less than the run of the straight portion.
Landings of no less than 2 feet, 6 inches should be provided at the top of any stair run with a door that swings toward the stair. A continuous handrail should be installed on at least one side of each flight of stairs that exceeds three risers. Stairs that are open on both sides, including basement stairs, should have a continuous handrail on one side and a railing on the open portion on the other side. Railings also should be in stalled around the open sides of all other interior stairwells, including those in attics.
On all exterior stairs, with the exception of those running to the basement of the house, the FHA prescribes the following: (1) that the width be that of the walk but that it be no less than 3 feet; (2) that the run be no more than 11 inches; (3) that the rise be no more than 7 1/2 inches and that all riser heights within a flight be uniform; and (4) that a continuous hand rail be installed on all open sides of stair flights to a platform more than four risers or 30 inches above finish grade.
Unprotected exterior stairs to the basement require the following ac cording to the standards set up by the MPS: (1) that the headroom be at least 6 feet, 4 inches; (2) that the width clear of the handrail be at least 2 feet, 6 inches; (3) that the run be no more than 7 1/2 inches; and (4) that a handrail be installed on at least one side if the stairs exceed four risers.
For protected exterior stairs to the basement, the MPS prescribes the following: (1) that the headroom be at least 6 feet, 2 inches; (2) that the run be at least 8 inches plus a 1 1/2 nosing; and (3) that the rise be no more than 8 1/4 inches.
The roof must be constructed first so that it will support its own weight plus that of loads from snow, ice and wind and also so that it will act as a base for the application of the roof finish materials. The most common systems of roof construction used in houses are trusses, joists and rafters, joists alone, planks and beams and panelized construction (see Figure 5.9).
A truss is made up of a number of individual boards (chords), usually 2 by 4 inches or 2 by 6 inches, arranged into a framework of triangles and connected by wood or metal gusset plates, metal gang-nail plates or metal ring connectors. Trusses usually are preassembled at a mill or on the ground. They are suspended between load-bearing walls spaced from 24 to 48 inches on center so that each truss acts as a unit to support the roof loads. Thus, they usually span the entire width of the house without additional support, allowing all the interior walls to be flexibly placed for they need not be load-bearing.
Joists are horizontal boards of from 2 by 4 inches to 2 by 8 inches that are suspended, with their narrow sides parallel to the ground, from exterior walls and often supported by interior bearing walls. Often when joists are used, rafters, usually of the same size, are erected as part of the framing system and run from the exterior bearing walls diagonally up ward to a ridge board or hip rafter.
If enough joists are used, they can be suspended between the exterior bearing wall and a ridge beam supported by an interior bearing wall, thus eliminating the need for the rafters.
Plank-and-beam roofs consist of 2-inch by 6-inch to 2-inch by 8-inch boards generally connected by cutting them tongue-and-groove so that they fit into a structural ridge beam and the exterior bearing wall beams. An alternate method used with plank-and-beam roofs is that of running them longitudinally, supported by the exterior wall and posts.
Panelized roof systems consist of pre-framed, precut and sheathed panels usually made up of 2-inch by 3-inch or 2-inch by 4-inch boards covered with plywood. In a stressed-skin roof panel, the plywood skins are bonded to the framing members under heat and pressure by glue- nailing techniques or by special adhesives. A sandwich panel is similarly constructed except that the faces are separated by weaker lightweight core materials instead of actual framing members.
Panels may be supported between transverse or longitudinal beams or may be centrally supported by bearing walls or beams as in joist roofs.
According to the MPS, the objective of roof sheathing is to provide safe support of roof loads without excessive deflection and to provide backing for the attachment of roofing materials. The most common types of sheathing are plywood, fiberboard and roof boards (planks). See Figure 5.10.
Plywood sheathing should be from 5 to 7 thick. The thickness of the plywood chosen depends on the type of plywood, the joist spacing and the roofing material to be used. The plywood is nailed or stapled to the frame.
Several good fiberboard sheathing materials are available that are in stalled similarly to plywood. When boards (planks) are used they should be at least 3/4 inch thick and not more than 12 inches wide, tongue-and- groove shiplap or square-edged. They are nailed either parallel to the rafters or diagonally across them. The roof boards should be nailed tightly to each other except in instances where single roofing is used in a climate where there is no snow. In these instances, the roof boards may be spaced the width of the board.
Whenever a roof is complicated by an intersection of the joining of two different roof slopes, adjoining walls or projections through the surface by chimneys or pipes or other protrusions, the joint must be flashed. Flashing usually is accomplished by first nailing metal strips across or under the point, then applying a waterproofing compound or cement and finally applying the roofing material over the edges to permanently hold it in place.
The objective of a roof covering is to prevent the entrance of moisture and to provide reasonable durability and economy of maintenance, ac cording to the MPS.
Shingles and shakes made of wood, asphalt, asbestos, cement, slate or tile are used for the majority of house roofs. However, metal roof, clay tile and built-up or membrane roofs also can be found. Figure 5.11 shows the construction of two types of roof covering, shingle and clay tile. Shingles are applied by nailing a double layer, known as a starter course, at the bottom of the roof and at the sides or rake of the roof so that they project at least 1 inch beyond the lower edge of the roof sheathing to enable rain to run clear of the roof. Each succeeding course or row of shingles then is nailed to the sheathing so that it covers the top of the row below, leaving part of the lower row exposed to the weather. The amount left exposed depends on the type of shingle, its length and the effect desired. The lines must be kept straight, however, and the joints must be staggered so that there is at least 1 or 2 inches of overlap to make the roof watertight.
There are various methods of joining the shingles and ridges, hips and valleys in conjunction with flashing materials to keep them water tight. Certain types of shingles, known as diamond, hexagonal and Dutch lap, are cut in special designs to reduce the amount of lap required and thus save material. These shingles are installed according to individualized, special instructions.
Slate is laid over the sheathing, which is covered with special impregnated slater’s felt. A cant strip is nailed to the lower end of the eave and the starter course is nailed down with the long side parallel to the eaves. The second course, as well as each succeeding course, is nailed down with copper or zinc nails so that at least three inches overlap the course below it. Several different techniques are used with flashing to make the ridges, valleys, hips and rake waterproof. The application of tile shingles varies with the type of tile being used. Some type of cant strip and roofing strip, however, is required with almost every kind of tile shingle.
Shingle tile is applied to the roof in the same manner as slate. A cant strip is nailed to the edge of the eave and the tiles are nailed through pre drilled holes in successive overlapping courses with copper nails. Special cut tiles are used for the ridge and for the hips and valleys.
Interlocking tiles—French tile, Spanish tile, Mission tile, Roman tile and Greek tile—are designed to provide maximum coverage with minimum material. The interlocking ridges on each side of the tile reduce the amount of lap needed for water-tightness and hold the tile together.
The closest design to a flat tile is the French tile. The bottom row is laid on top of a cant strip. Specially shaped pieces are used at the hip, ridge and valleys. The tiles are nailed and cemented. Mission tiles and Spanish tiles are installed by turning each adjacent tile alternately con cave (“pans”) and convex (“covers”) so that the covers fit down over the upturned edges of the pans. Then they are nailed with a single nail at the upper end. The convex tiles rest on 1-inch by 4-inch wood strips set on edge, running from eave to ridge. Specially shaped pieces are used at the ridge, rake, hips and valleys. Both Green tile and Roman tile are combinations of flat tile with upstanding outer edges and curved or angular covers that are tapered so that succeeding courses fit snugly.
Roll roofing is applied by nailing it down in strips that lap and then sealing the laps with roofer’s cement. At the eaves and rakes, the roofing is bent over the roof board, nailed down and bent over the top of the ridge. Sometimes, when the roof is to be walked on, duckboards are laid over the roofing to protect it.
Water may leak through the roof for a variety of reasons. Asphalt shingle roofs may leak during a high wind if light-grade shingles are used. As these shingles get older, they curl and tear and become pierced with holes. Wood shingles may curl and split, become loose and broken and fall off the roof, while asbestos shingles may crack and break. Metal roofs can rust, become bent and pierced with holes. Roll and built-up roofs may be come loose, torn, patched and worn through.
A fireplace with logs burning in the hearth still provides a strong roman tic appeal. Basically an amenity in most American homes rather than a heating system, the fireplace usually is constructed of masonry. There are many fireplace designs and variations, of which the simplest and most common is the single opening with a damper and hearth. Other designs, however, feature two, three or four openings. Figure 5.12 shows four fire place types.
The opening of the fireplace should be wider than it's high, but it shouldn't be very deep because the shallower the fireplace, the more heat is reflected into the room. The inside walls should go back at an angle so that the rear inside wall is at least 1 1/2 feet narrower than the front opening because square inside corners interfere with the air flow and cause smoking and poor combustion. The rear inside wall should slope forward to the back of the damper.
A damper is a desirable feature. It should be at least 8 inches above the top, but it shouldn't be set directly on top of the fireplace opening because such a position may, at times, allow smoke to escape into the room. Another desirable feature is an ash dump connected to an ash pit with an ash-cleanout door.
A well-designed smoke shelf, at least 4 inches wide, stops the cold air that flows down the inside of the chimney flue from blocking the flow of smoke upward. The cold air flow is turned back upward, causing it to mix with the rising warm air and smoke.
The smoke chamber is the large space above the damper and smoke shelf. The back is straight, but the sides start at the ends of the damper and slope inward to the two inner sides of the flue. The rate of slope is about 7 inches inward to each 12 inches of height.
The inner hearth (really the back hearth under the fire), together with the cheeks and the back of the fireplace, must be built of heat- resistant materials to withstand the intense heat of the fire. Thus, fire- brick and fireclay are the most commonly used materials. A front hearth extending at least 16 inches from the front of the fireplace and at least 8 inches beyond each side is needed as a precaution against flying sparks. Because this hearth, which usually is supported by a trimmer arch or concrete slab, must be fireproof, it often is made of tile, brick or stone.
CHIMNEYS and VENTS
Chimneys and vents should be constructed and installed to be structurally safe, durable, smoke-tight and capable of withstanding the action of flue gases.
The efficiency of any heating system (except electric) depends on the chimney or vent. Defective chimneys and vents may become serious fire hazards. A chimney may be a simple flue or an intricate masonry construction consisting of heater flues, ash pits, incinerators, ash chutes, fireplaces and fireplace flues. Figure 5.13 shows the typical construction of a masonry chimney.
Whatever its construction, the chimney is the heaviest portion of the house and it must be supported by its own concrete footings. The footings must be designed so that the chimney will not settle faster than the rest of the building.
The masonry chimney walls should be 8 inches thick when they are exposed to the exterior of the house. The space between flues, when there is more than one flue in a chimney, is called the wythe. In the best construction, this space is solidly filled with brick and the joints are slushed full of mortar at least 4 inches thick. As the MPS prescribes, “Masonry and factory-built chimneys shall extend at least 2 feet above any part of a roof, roof ridge or parapet wall within 10 feet of the chimney” and “masonry chimney walls shall be separated from combustible construction.”
A 2-inch airspace filled with fireproof material is recommended. At the bottom of the chimney should be an ash pit with a cleanout door into which run the flues from the fireplaces.
Flues from the furnace and hot-water heater shouldn't run into the ash pit because cold air below the smoke-pipe connection will interfere with the draft in the flue. A cleanout door should be close below the junction of the smoke pipe and the chimney.
The furnace and hot-water heater are connected to the chimney by a smoke pipe through a metal or terra-cotta collar built into the brickwork. The smoke pipe is slipped into the collar to a point where its end is just flush with the inside wall of the flue. If extended in error too far into the flue, the efficiency of the draft will be reduced substantially. For fire safety, the smoke pipe should be at least 10 inches below the floor joists and the joists should be further protected with plaster or a shield of metal or asbestos. According to the MPS, “The smoke pipe shouldn't exceed 10 feet in length or 75 % of the vertical height of the chimney, whichever is less.”
The heart of the chimney is the vertical open shaft through which the smoke and gas pass from the fire to the outside air. The size of the flue required for the best combustion efficiency depends on the size of the fireplace or furnace, its design and the type of fuel being used.
The warm air or smoke rises up the flue. It ascends in spirals and occupies the greater part of the center of the flue. A rough surface retards this upward flow. The best way to overcome the roughness is to use a flue lining. The most common shapes for flue linings are circular, square and rectangular. A square or rectangular flue is less efficient than a round one. Its capacity is only the same as a round flue that would fit inside it. Thus, the main reason shapes other than circular are used is for ease of construction. A single flue, however, shouldn't be used for more than one heating device.
The flue should extend a few inches out of the top of the chimney wall. The top of the wall is capped with concrete, metal, stone or other non-combustible, waterproof material sloped from the flue to the outside edge. The cap should be at least 2 inches thick at the outside edge, according to the MPS.
Another type of chimney is made and assembled off the premises in a factory. Many of the prefabricated units consist of a flue liner encased in a concrete wall. The units should be approved by Underwriters’ Laboratories and should be the proper size and design for the appliance to be used.
GUTTERS and DOWNSPOUTS
Gutters and downspouts provide means for the controlled water disposal from roofs to prevent damage to the property or to prevent the unsightly appearance of walls when roof overhangs aren't provided. The MPS states that gutters are needed when either the soil is of such a nature that excessive erosion or expansion might occur or if the roof overhangs are less than 12 inches in width for one story or 24 inches in width for two stories. If gutters aren't provided in these instances, a diverter or another means must be provided to prevent water from roofs or valleys from draining on uncovered entrance platforms or steps.
Gutters, or eaves troughs, catch the rainwater as it reaches the edge of the roof and carry it to the downspouts or leaders. In northern climates, gutters must be installed below the slope line so that snow and ice can slide clear.
Metal gutters, which are attached to the house with various types of metal hangers, are the most common type now being made. Aluminum, copper, galvanized iron and other metals are used in the construction of these gutters, the size of which is determined by the size of the roof served and the rainfall of the area. Figure 5.14 shows gutter construction.
Wood gutters still are used, however, mostly in the Northeast. The most common types are cut from solid pieces of wood such as Douglas fir, cypress and redwood cedar. A wooden gutter is shaped with a semicircular channel inside and an ornamental molding (ogee) on the outside and it sometimes is completely or partially lined with metal. Care must be taken when two pieces of gutter are joined together to prevent the joint from leaking and rotting. Thus, the joint should be covered with a piece of metal embedded in elastic roofers cement.
Wood gutters are attached to the house with non-corroding screws bedded in elastic roofers cement to prevent leakage. Built-in gutters are made of metal and set into the deeply notched rafter a short distance up the roof from the eaves. Pole gutters consist of a wooden strip nailed perpendicularly to the roof and covered with sheet metal.
Downspouts or headers are vertical pipes that carry the water from the gutter to the ground and sometimes into sewers, dry wells, drain tiles or splash pans. Their most common shapes are rectangular, corrugated rectangular, corrugated round and plain round. They must be large enough to carry the water away as fast as they receive it.
The junction of the gutter and the downspout should be covered with a basket strainer to hold back leaves and twigs, especially if the gutter is connected to a storm or sanitary sewer that may become clogged and may be difficult to clean out.
The objective of wood floor framing is to provide floor construction that will assure the safe and adequate support of all loads and also to eliminate objectionable vibrations, according to the MPS.
Floor framing is relatively simple and the same regardless of the general framing method used for the rest of the house. Basically, floors consist of subflooring resting on joists (floor beams) stiffened by bridging; the joists are carried by girders, walls or load-bearing partitions.
In narrow houses, the joists can run from exterior wall to exterior wall. Usually at least one girder also is required. Girders generally are supported by wooden posts, brick or block or poured-concrete piers, hollow steel pipes (Lally columns) or steel pipes filled with concrete. All these supports must rest on an adequate footing and must have a suitable cap on which the girder rests.
Most house girders are made either of wood or steel “I” beams. Wood girders can be solid pieces of timber or built-up beams consisting of 2-inch or 3-inch boards standing on edge and spiked or lag screwed together to form a larger piece. The use of solid girders has substantially de creased in recent years because of their increase in cost and tendency to split (check) more easily than built-up ones. Another advantage with built up girders is that, by spacing the joints, the beam can be made continuous and thus run unbroken from one end of the house to the other.
The use of at least one steel I beam is quite common. These beams are handled in the same manner as wood beams except that they usually come in sections and are bolted together. They should be covered with 1 inch of cement, however, to protect them from heat in the event of a fire because relatively little heat (only about 500 degrees to weaken and 1,000 degrees to buckle) can cause such a beam to lose its ability to hold the joists
According to the MPS, the objective in subflooring is to provide construction that will assure the safe support of floor loads without excessive deflection and to provide adequate underlayment for the support and attachment of finish flooring materials.
Plywood is the most common material now being used for subflooring. When properly installed with the grain of the outer piles at right angles to joists and staggered so that the division between adjacent panels comes over different joists, plywood is as good as boards or planks.
Wood boards with a minimum thickness of ¾ of an inch and a maxi mum width of 8 inches may be installed diagonally to or at right angles to Joists If the boards are installed at right angles to the joists, the finish floor should be installed across the subflooring
Plank and beam floor systems usually are made with 2-inch by 6- inch or 2 inch by 8-inch tongue-and-grooved or splined planks spanning between beams generally spaced 4 to 8 feet on center The planks serve as the subfloor and working platform and transmit the floor loads to fewer but larger members than in wood joist floor systems.
Panelized floor systems are increasing in popularity. Panels are either pre-manufactured in the mill or on the job site and are set in place over the joists. Stressed-skin floor panels are made with framing members to which plywood skins are bonded either by the glue-nailing techniques or by adhesive applied under heat and pressure. Sandwich panels are similar, but the faces are glued to and separated by weaker lightweight core materials instead of actual framing members. A few houses also are made with steel and concrete subflooring systems.
To stiffen the joists and prevent them from deflecting sideways, strips of wood or bands of metal are fastened crosswise between the joists and are nailed top and bottom to form the bridging. There should be a line of bridging for each 6 to 8 feet of unsupported length of joist.
Carpeting, which can be installed over either finished flooring or sub- flooring, is rapidly gaining in popularity as a floor covering because manufacturers claim that it can be used in every room in the house. Thus, the FHA has reversed its former position on carpeting and now considers it part of the real estate.
Rubber-backed carpeting is glued with a special glue to the flooring or subflooring. Once down, it's hard to remove without damaging the carpet and the finished floor beneath. Jute-backed carpet, on the other hand, is installed over a carpet pad. It can be fastened down at the edges with tacks or by installing a tackless strip around the perimeter and attaching the carpet to it. Tackless strips can be glued to concrete and other hard surfaces. In either case, the carpet must be stretched to eliminate wrinkles or buckles.
Ceramic tile can be set in plaster. A waterproof building paper and then wire mesh is laid over the subflooring. The setting bed of plaster must be 1¼ inches thick. (An alternate process is attaching the rough flooring to strips below the top of the joists that are beveled and extend into the plaster bed; the plaster bed must be 1¼ inches over the top of the joists.) On top of this, a 1/8-inch skim coat is applied. The tiles are soaked in water and then pressed firmly in place in the plastic setting bed. Mortar is compressed into joints, which are tooled the same day the tile is set, and then covered with waterproof paper and damp core.
Ceramic tile also can be attached with special adhesive to a smooth concrete floor or to a subfloor covered with a special adhesive or special underlayment material. The following steps are used for this method of installing ceramic tile. Before applying the tile, the entire surface is sealed with a suitable water-resistant sealer or a coat of tile adhesive. Then tile adhesive is applied to the surface with a notched spreader blade. The tile is set by the floating method, using a slight twisting motion. Before the grouting, time is allowed for the volatiles from the adhesive to evaporate. Grout is forced into joints, with care taken to leave no open joints. Then the joints are tooled.
Concrete slabs may be used for floor covering with no further treatment, painted with special concrete paint or covered with other flooring coverings. Resilient tiles are glued down with special adhesives according to the individual manufacturer’s recommendation for a particular tile. The tiles must not be installed directly over a board or plank subfloor. A suitable underlayment first must be installed.
Terrazzo flooring is made of colored marble chips mixed into cement. After being laid, it's ground down to a very smooth surface. There are two basic methods of installation: the unbonded method, where the cement is separated from the subfloor by an isolation membrane; and the bonded method, where the cement is bonded directly to the subflooring. In both methods, metal divider or expansion strips are installed to pre vent cracking.
Wood block flooring may be installed over an underlayment or directly to most sub-floorings. According to the MPS, “The blocks are nailed with at least two nails in each tongued side (four per block), driving the nail at an angle of 40 to 50 degrees. They also may be installed by attaching them to a suitable underlayment with special adhesives. When installed over concrete, the concrete should be first sealed with a primer compatible with the adhesive.”
Wood strip flooring may be installed directly over the joists or over the subflooring. When installed directly to the joist, hardwood must be 25/32 of an inch thick and not more than 2 1/4 inches wide. Softwood al ways must be at least 25/32 of an inch thick and installed at right angles to the joists. Each flooring strip should bear on at least two joists. Approximately 1/2 of an inch of clearance should be provided between the flooring and the wall to allow for expansion. The flooring is blind-nailed to each joist with a threaded or screw-type nail, driving the nail at an angle of approximately 50 degrees.
The boards over wood flooring are nailed at right angles to the sub- flooring except when the subflooring is plywood or is laid diagonally. A layer of 15-pound asphalt-impregnated felt or another suitable building paper should be placed on top of the subflooring to prevent drafts, dust and moisture from coming up through the strips. The flooring should be blind-nailed, driving nails at an angle of 40 to 50 degrees.
Flooring must be kept dry at all times. It often is kiln-dried to a low moisture content of 6 to 8 % and must be kept that way. Flooring that's moist when it's laid shrinks in the dry winter, leaving ugly joints. After the flooring is laid, it's scraped, sanded and varnished.
Random-width flooring of various lengths is laid to resemble old floors. In this process, the boards are blind-nailed or pegged to simulate old floors. This flooring is available prefinished with nail holes to decrease the possibility of damaging it during installation. Plywood with special surface coatings and finishes is nailed down like any other flooring.
Other types of flooring include the many attractive vinyl tiles that now are available, rubber tiles, asphalt tiles and rolled goods such as linoleum.
Figure 5.15 illustrates subfloors and floor coverings.
Weak and Defective Floors
Sagging and sloping floors can be caused by defective framing. There are, however, other reasons for floor troubles. The rest of the house framing may be fine and it may be just the floor joists that are too small or lack support because inadequate bridging is causing sagging or sloping. Poor carpentry in one area, however, usually is a tip-off to poor carpentry throughout the house.
Floors that have been exposed to water may warp and bulge upward. Wide cracks between the floorboards are a sign of poor workmanship or shrinkage caused by wood that was improperly dried or not stored correctly at the time of installation. Fortunately, rough, stained, discolored, blemished, burned or gouged floors usually can be cured by refinishing.
FIRE PROTECTION and SAFETY
The following is a summary of the major items that the MPS requires a house to have to make it safe from fire. When houses are built to the lot line or with party walls such as in a town house, the party or lot-line wall must extend the full height of the building without any openings and must not have less than a two-hour fire-resistance rating.
Fire-stopping is required in concealed vertical spaces in walls and partitions at each floor level and at the ceiling of the uppermost story. Fire-stopping should be of wood blocking, wood construction or non- combustible material. If wood, it should be a minimum thickness of 2 inches. If of a material other than wood, the fire-stopping should provide equivalent protection.
Fireplaces should be supported on concrete or other masonry but not on wood framing. A separate flue is required for each fireplace. Where a lining of firebrick at least 2 inches thick is provided, the total thickness of the firebox wall, including lining, should be not less than 8 inches. Where firebrick lining isn't provided, the thickness should be not less than 12 inches. and steel fireplace lining at least 1/4 of an inch thick may be used in lieu of brick lining.
The fireplace walls and chimney should be separated from combustible construction by a 2-inch airspace from all framing members; this air space should be fire-stopped at floor level with an extension of the ceiling finish, strips of asbestos board or other noncombustible material.
Every fireplace should have a damper that effectively closes the flue passage. Smoke chambers less than 8 inches thick should be parged with fireclay mortar (not masonry mortar) on all sides.
A hearth supported with noncombustible material made out of fire-brick, brick, concrete, stone, tile or any other noncombustible heat-resistant material should extend at least 16 inches in front of the fireplace opening and 8 inches on each side. Combustible material shouldn't be placed within 3 1/2 inches of the edges of a fireplace opening. Combustible material above and projecting more than 1 1/2 inches in front of the fireplace opening should be placed at least 12 inches above the opening.
Factory-built fireplaces and their chimneys should be labeled and approved by Underwriters’ Laboratories, Inc., and installed according to the conditions of the approval. The outer hearth for factory-built fire places should be made of noncombustible material not less than 1/8 of an inch thick and may be placed on the subfloor or the finish floor.
Chimneys should, of course, be constructed of fireproof materials. Smoke pipes should be constructed of a fireproof material equivalent to U.S. standard 24-gauge steel. Factory-built chimneys should be listed by Underwriters’ Laboratories and installed in exact accordance with the listing. Chimneys should extend at least 2 feet above any part of a roof or roof ridge or parapet wall within 10 feet of the chimney.
Smoke pipes and flues should have a maximum length from the appliance outlet to the chimney of 10 feet or 75 % of the chimney height, whichever is less. Fireclay flue lining should be installed in all masonry chimneys less than 8 inches thick. Heating equipment construction and installation should comply with published industry standards.
Domestic cooking ranges should be installed so that there is a mini mum of 2 feet, 6 inches of clearance between the top of the range and the bottom of all unprotected wood or metal cabinets over the range. A 2- foot minimum clearance is acceptable when the bottom of the cabinet is protected with at least 1/2-inch asbestos mill board covered with not less than 28-gauge sheet metal (.015 stainless steel, .024 aluminum or .020 copper). The distance from the cooking surface to the bottom of the hood should be not less than the maximum projection of the hood from the wall. The minimum distance from the edge of a burner to a wall or cabinet should be 10 inches.
Other Safety Hazards
The number of household accidents is staggering and unfortunately many of them result in death or serious injury.
Here are a few of the common causes of household accidents that can be eliminated:
1. Closets and cupboards that latch shut so that they can be opened only from the outside and can trap children inside.
2. Doors that open out over stairs without a landing.
3. Steep, poorly lit basement stairs without a handrail.
4. Bathroom light fixtures with pull strings or switches that can be reached from the tub or shower.
5. Swimming pools that aren't 100 % fenced in, with at least a 4-foot fence and a gate that locks (this applies to neighbors’ pools, too).
6. No adequate convenient space to lock up dangerous cleaning products, medicines and other poisonous substances so that young children can't get at them.
7. Too little headroom on stairs.
8. Porches, patios and stairwells without strong handrails around them.
9. Changes in floor levels in the house with a difference of only one or two steps.
10. Stair risers of unequal size.
11. Stairs without adequate lights that can be turned on and off from both the top and the bottom of the stairs.
PROTECTION AGAINST TERMITES and DECAY
The subterranean termite (see Figure 5.16) is an insect that attacks in colonies and derives its nourishment from cellulose materials such as wood, fabrics, paper and fiberboard. To obtain nourishment, the termite may attack wood structures above the ground by means of shelter tubes attached to foundation walls, piers and other construction members in con tact with the ground. Only under conditions that permit the insect to establish and maintain contact with soil moisture, however, is a colony able to penetrate and consume wood in service. This requirement indicates that a barrier separating the wood from the earth, supplemented by an inspection, is a practical and effective method for preventing damage by termites.
Protection of wood structures to provide maximum service-life involves three methods of control that can be handled by proper design and construction. One or more of the following methods may be employed:
1. Controlling the moisture content of wood.
2. Providing effective termite barriers.
3. Using naturally durable or treated wood.
According to the MPS, the objective is to provide protection of wood materials from damage by termites and decay by applying suitable construction methods and control measures. It is possible by careful plan- fling and attention to construction details to produce a frame house that will resist damage by subterranean termites and fungi that produce decay. Control of the moisture content of the wood is a practical and effective method for prevention of decay.
The extent of termite control that's needed is determined by local conditions. Generally, termite control is required in all states except Alaska, Maine, New Hampshire, Vermont, Michigan (except the very southern part), Wisconsin, Minnesota, North Dakota, South Dakota, Montana, Wyoming, Washington, Oregon, Idaho and the northern parts of Nevada, Utah, Colorado, Nebraska, Iowa and New York.
For effective termite control, the following steps should be taken during construction:
1. All roots, wood forms and scraps of lumber should be removed from the immediate vicinity of the house before backfilling and be fore placing a floor slab. Particular care should be taken to remove all scraps of lumber from enclosed crawl spaces.
2. The building site should be graded to provide positive drainage away from foundation walls.
3. Provisions should be made for moisture-proofing the foundation walls in the manner described in the foundation section of this section.
4. Adequate roof and wall flashing should be provided for in the manner described in this section’s roof and wall section.
5. In crawl spaces, the clearance from the lowest wood joists or planks should be 18 inches and from the bottom of wood girders or wood posts, 12 inches.
6. In basements or cellars, wood posts that support floor framing should rest on concrete pedestals extending 2 inches above concrete floors and 6 inches above earth floors and separated by an impervious barrier.
7. Main beams or girders framing into masonry walls should have ½ of an inch of airspace at the top, end and sides.
8. Wood sills that rest on concrete or masonry exterior walls should be at least 8 inches above the exposed earth on the exterior of the building.
9. Wood siding and trim should be at least 6 inches above the exposed earth on the exterior of a structure.
10. In exterior steps, the structural portions of wood stairs, such as the stringers and posts, should be at least 6 inches above the finish grade.
11. In porches and breezeways and on patios, the beams, headers and posts supporting the floor framing should be at least 12 inches above the ground. Floor joists should be at least 18 inches above the ground. Posts that rest on wood, concrete or masonry floors should be supported on pedestals extending at least 2 inches above the floor or at least 6 inches above the exposed earth.
12. Planters, concrete steps or porch slabs resting on the ground should be below the top of the foundation or they should be separated from the wood in the main structure by at least 2 inches or otherwise protected from concealed termite penetration.
13. The ends of main structural members exposed to weather and supporting roofs or floors should rest on foundations that provide a clearance of at least 12 inches above the ground or 6 inches above the concrete.
14. Shutters, window boxes and other decorative attachments should be separated from the exterior siding to avoid trapping rainwater.
15. Adequate ventilation should be provided to prevent condensation in enclosing spaces as described in the ventilation section of this section.
Termite barriers (see Figure 5.17) are provided by any building material or component that can be made impenetrable to termites and that drives the insects into the open where their activities can be detected and eliminated. When there are adequate separation clearances as previously de scribed, termite barriers shouldn't be needed except in very heavily infested areas.
Following are the five types of termite barriers employed when needed:
1. Preservative-treated lumber for all floor framing up to and including the subfloor. For this purpose, pressure treatment with an approved preservative is recommended.
2. Properly installed termite shields. These should be made of not less than 26-gauge galvanized iron, or another suitable metal of proper thickness, installed in an approved manner on top of all foundation walls and piers and around all pipes leading from the ground. Longitudinal joints should be locked and soldered. Where masonry veneer is used, the shield should extend through the wall to the outside face of the veneer.
3. Chemical soil treatment. The following chemical formulations have been found to be successful and are recommended: aldrin, 0.5 per cent in water emulsion or oil solution; benzene hexachloride, 0.8 per cent gamma in water emulsion or oil solution; chlordane, 1 % in water emulsion or oil solution; dieldrin, 0.5 % in water emulsion or oil solution. In general, water emulsions aren't injurious to plants. Applications of chemicals and precautions involved in their use should be made according to manufacturers’ recommendations.
4. Poured concrete foundations, provided no cracks greater than 1 of an inch are present.
5. Poured, reinforced concrete caps, at least 4 inches thick, on unit masonry foundations, provided no cracks greater than 1/64 of an inch occur.
Slab-on-ground construction requires special consideration in areas where the termite hazard is a significant problem. Concrete slabs vary in their susceptibility to penetration by termites; thus, they can't provide adequate protection unless the slab and supporting foundation are poured integrally to avoid cracks or holes through which termites may enter.
Where other types of slab construction are used, termites may penetrate through the joints between the slab and the wall. They also may enter through the expansion joints or the openings made for plumbing or conduit. Thus it's necessary at these points to provide a barrier either by using termite shields, coal-tar pitch or chemical soil treatment.
Masonry veneer in contact with the ground may provide access for termites in infested areas. For this reason, the veneer should be kept at least 8 inches above the finished grade unless termite shields are installed in an approved manner or the soil on the exterior has received a chemical treatment.
Naturally durable or treated wood should be used when the member is so located that it can't be maintained at a safe moisture content or where climatic or site conditions are such that construction practices alone aren't sufficient for the control of decay or termites. This type of wood should be used where wood is embedded in the ground, where it's resting on concrete that's in direct contact with the earth or where it's not possible to maintain the recommended separations between the wood and the earth.
Woods that are naturally decay-resistant are bald cypress (tide-water red), cedar, redwood, black locust and black walnut. Termite-resistant species are redwood, bald cypress and eastern red cedar.
Wood may be treated by the pressure method in which it's impregnated with toxic chemicals at elevated pressures and temperatures in a re tort. Wood may be preservative-treated by the non-pressure process of cold soaking, by the vacuum process or by the hot-and-cold bath method. It is best not to cut the wood after it has been treated. If cutting is necessary, however, the new surfaces must be treated with a liberal application of the preservative used in the initial treatment.
The best way to check for termites is to hire a professional. The FHA, Veterans Administration (VA) and other lending institutions re quire professional termite inspections in many areas of the country.
Termites work slowly. If they are caught in the early stages of infestation, they may be stopped for a few hundred dollars. Damage caused in the more advanced stages of infestation may cost thousands of dollars to repair.
Maintenance inspections of the house at least annually in the spring will detect problems at an early stage. Such inspections should concentrate on three specific areas: the foundation, including crawl spaces; the attic spaces and roof; and the exterior surfaces, joints and architectural details. When termite shelter tubes are discovered, they should be destroyed and the ground below should be poisoned. When evidence of termites is discovered, a professional exterminator should be employed to correct the problem. If dampness is noticed, proper clearances between the wood and the ground should be reestablished and vents should be checked and repaired.
Carpenter ants don't actually cut wood, but they tunnel into the wood to make their nests. They tend to damage wood that's soft because of dampness and previous rotting.
PAINTING and DECORATING
When painting and decorating a house, the objective should be to provide a coating that will provide adequate resistance to weathering, protection from damage by corrosion, reasonable durability, economical maintenance and an attractive appearance.
All paints or other coatings should be standard commercial brands with a history of satisfactory use under conditions equal to or similar to the conditions present in the area concerned.
Application of paint or other coating should be in strict accordance with manufacturers’ directions. Ready-mixed paint shouldn't be thinned, except as permitted in the application instructions. Exterior painting should be done only in favorable weather. All surfaces should be free of dew or frost and must be dry to the touch except with certain masonry paints formulated for application to wet surfaces. Painting shouldn't be done when the temperature is below 40 degrees. All surfaces to be finished should be clean and free of foreign material such as dirt, grease, asphalt or rust.
Application should be made in a workmanlike manner to provide a smooth surface. Additional coats may be required if the finish surface does not provide acceptable coverage or hiding. Certain pigments provide excellent hiding ability even when thinly applied. With paints of this type, care must be taken to obtain adequate coverage if the coating is to offer reasonable durability.
Figures 5.18 to 5.22 indicate the proper preparation, priming and finish coating recommended by the FHA for various surfaces inside and outside of a house.
FIGURE 5.18 Interior Wood, Metal and Concrete Surfaces
1. When used in kitchen or bathroom, must provide a durable, waterproof finish.
2. be left unfinished.
3. be left unfinished in uninhabitable rooms and their closets and when covered with other floor material.
FIGURE 5.19 Interior Walls and Ceilings
FIGURE 5.20 Exterior Wood Surfaces
1. Factory-applied finishes of comparable quality also acceptable.
2. Made of edge-grain redwood or red cedar, may be left unfinished.
Caution: Natural finishes or surface-coated finishes (for example, varnishes and synthetics) should be used only on surfaces that aren't directly exposed to rain or sunlight. Varnish, if used, should be spar varnish formulated for exterior use; not less than two coats should be applied. Penetrating finishes such as sealers, oils, pigmented oils and water repellents should be used on surfaces exposed to sunlight or rain.