Installing Hardwood Floors

The installation of hardwood flooring is, in one way, complex. The variety of types, sizes, and application systems is so great that there are literally dozens of ways to install hardwood floors. Once you’ve selected the type of flooring, however, the installation becomes much easier. Each type of hardwood flooring has its own installation methods, and manufacturers and dealers are usually helpful in offering instructions.

The purpose of this section is to guide you through the installation of strip, block, and other types of hardwood flooring so that you can do a professional-looking job — even if you’ve never worked with wood before. More than 50 illustrations will show you exactly how it’s done.


Figure 3-1 illustrates the installation of wood-strip flooring over a concrete slab floor. Since this type of flooring tends to be cold and plain, many people install wood flooring over the top. First, be sure that there is sufficient insulation and a vapor barrier between the slab and the ground, or at least the slab and the flooring. The anchored sleepers in the illustration are intended to allow space between the cold slab and the hardwood floor. Insulation can be installed here, if you desire.

Another way of installing strip flooring over a concrete slab is offered in Fig. 3-2. This method allows a greater air pocket between the concrete and the flooring and includes a waterproof coating and vapor barrier to retard moisture, which is flooring’s worst enemy Nailing must be more precise in this method to make sure that the flooring is anchored to the sleepers. This can be accomplished by using a chalk line to mark the nailing line or by careful nailing.

Fig 3-1: Wood-strip flooring over a concrete slab.

Fig 3-2: Alternate installation over a concrete slab.

Fig. 3-3: Flooring installation at finish grade.

In both cases, be sure that the treated lumber won’t rot and eventually destroy your flooring from below.

Figures 3-3 and 3-4 illustrate the installation of flooring over a concrete slab at and below finish grade. I cover the installation of wood flooring over a concrete slab in more detail in the coming pages.

In most cases, strip and block flooring will be installed over a wood subflooring, as discussed in the last section. The typical wood-subfloor system (FIG. 3-5) includes the floor joists, subfloor, building paper, and finish flooring. The flooring should be installed at a 45- or 90-degree angle (FIG. 3-6) to the subflooring.


Most hardwood flooring has been kiln-dried to the proper moisture con tent. To maintain the moisture level, don’t truck or unload it in rain, snow, or excessively humid conditions. Cover it with a tarpaulin or vinyl if the atmosphere is foggy or damp.

Check the job site before the flooring is delivered. Be sure that the flooring will not be exposed to high humidity or moisture. Surface drain age should direct water away from the building. Basements and crawl spaces must be dry and well-ventilated. In joist construction with no basement, provisions for outside cross ventilation must be provided through vents or other openings in the foundation walls. The total area of these openings should equal 1 1/2 percent of the first floor area. A ground cover of 4- or 6-mil polyethylene film is essential as a moisture barrier.

Flooring that is installed over a heating furnace or uninsulated ducts may develop cracks unless protection from the heat is provided. Use a double layer of 15-pound or a single layer of 30-pound asphalt felt or building paper, or 1/2-inch standard insulation board between the joists under the flooring in these areas. Insulation that is used over a heating plant should be nonflammable.

Fig. 3-4: Flooring installation below finish grade.

Fig. 3-5: Typical wood subfloor system.

Fig. 3-6 Installing strip flooring at a 90-degree angle to subflooring

Before flooring is delivered, the building should be closed in, with outside windows and doors in place in a newly constructed home. All concrete, plaster, and other masonry should be thoroughly dry

In warm months, the building must be well-ventilated. In winter, a temperature of 65 to 70 degrees Fahrenheit (not higher) should be maintained at least 5 days before the flooring is delivered for best results.

When job conditions are satisfactory, have the flooring delivered, broken up into small lots, and stored in the rooms where it will be installed. Allow 2 to 3 days for the flooring to become acclimated to the job site. Such protection from heat, cold, and moisture extremes may seem wasteful, but they will pay off during the installation and maintenance of your hardwood floors.


All types of hardwood flooring can be installed successfully over a concrete slab. The slab must be constructed properly, however, and the instructions below followed precisely.

Watch out for water. New concrete is heavy with moisture, an inherent enemy of wood. Proper on-grade slab construction requires a vapor barrier between the gravel fill and the slab. While this barrier prevents moisture from entering through the slab, it also retards the curing of the slab. So test for dryness, even if the slab has been in place over 2 years. To guide you, here are a few methods that professional builders and hardwood-flooring installers use to test concrete for moisture.

The rubber mat test. Lay a flat, non-corrugated rubber mat on the slab, place a weight on top to prevent moisture from escaping, and allow the mat to remain overnight. If there is trapped moisture in the concrete, the covered area will show water marks when the mat is removed. This test is only useful if the slab surface was originally light in color.

The polyethylene film test. Tape a 1-foot square of heavy, clear polyethylene film to the slab and seal all the edges with plastic packaging tape. If, after 24 hours, there is no clouding, or drops of moisture on the under side of the film, the slab can be considered dry enough to install wood floors.

The calcium chloride test. Place 1/4 teaspoon of dry (anhydrous) calcium chloride crystals, which are available at drug stores, inside a 3-inch diameter putty ring on the slab. Cover with a glass so that the crystals are totally sealed off from the air. If the crystals dissolve within 12 hours, the slab is too wet for a hardwood-flooring installation.

Keep in mind that the test should be made in several areas of each room and on both old and new slabs. The remedy for a moist slab is to wait until it dries naturally or to accelerate the drying process with heat and ventilation.

Vapor barrier

Start with a good vapor barrier. To be absolutely certain that moisture doesn’t reach the finished floor, a vapor barrier must be used on top of the slab. Its placement depends on the type of nailing surface and/or the type of wood flooring to be used. Prepare the slab by sweeping it clean. The slab must be sound, level, and free from grease, oil stains, and dust. Level out any high spots and fill the low spots.

Plywood-on-slab method

This system uses 3/4 or thicker exterior plywood as the subfloor nailing base over the concrete slab. Refer to FIG. 3-7.

Fig. 3-7: Installing a plywood subfloor over a concrete slab

Roll out a 4-mil or heavier polyethylene film over the entire slab. Overlap the edges from 4 to 6 inches and allowing enough to extend under the baseboard on all sides. It does not need to be embedded in mastic.

Loosely lay plastic panels over the entire floor. Cut the first sheet of every run so that end joints will be staggered 4 feet. Level a 1 space at all the wall lines and 1/4 about a 1/8 space.

Fasten the plywood with a powder-actuated concrete nailer or hammer-driven concrete nails. Use a minimum of nine nails per panel. Start at the center of the panel and work toward the edges, so that you are sure to flatten out the plywood and hold it securely

An alternate method is to cut the plywood into 4 x 4-foot squares, score the back of each square, and then lay on mastic adhesive. This method, however, will require the use of either of two types of moisture barriers that can be laid in mastic. These will be described later in this chapter.

Fig. 3-8 Screeds method of installing flooring over concrete slab.

Screeds method

The screeds method of installing strip flooring on a concrete slab is shown in FIG. 3-8. This method uses flat, dry 2 x4-inch screeds, or sleeps, of random lengths from 18 to 48 inches. They must be preservative- treated with a product other than creosote, which might bleed through and stain the finish floor.

Sweep the floor clean, prime it with an asphalt primer, and allow it to dry. Apply hot, poured asphalt mastic and embed the screeds, 12 to 16 inches on center, at right angles to the direction of the finished floor. Stagger the joints and lap ends at least 4 inches. Leave a 3 space between the ends of the screeds and the walls.

Over the screeds spread a vapor barrier of 4- or 6-mil polyethylene film with the edges lapped 6 inches or more. It is not necessary to seal the edges or to affix the film with mastic, but avoid bunching or puncturing the plastic, especially between screeds. The finish flooring will be nailed through the film to the screeds.

Some installers prefer to use a two-membrane asphalt felt or building- paper vapor barrier, which will be explained later. The screeds are laid in rivers of mastic on the asphalt felt or building paper. In this system, the polyethylene film over the screeds is recommended because of the extra moisture protection that is provided at a nominal cost.

The screeds methods alone—that is, without a subfloor and spaced 12 inches on center—is satisfactory for all strip flooring and plank flooring to a 4-inch width. Plank flooring wider than 4 inches requires either the plywood-on-slab subfloor outlined earlier or screeds plus a wood sub- floor in order to provide an adequate nailing surface. The subfloor may be 5/8 inch or thicker plywood or ¾ inch boards.

Installing block flooring over a slab

Parquet, block, herringbone, and similar floors are normally laid in asphalt mastic and thus don’t require a nailing surface on top of the slab. The need for a good moisture barrier is most important, however. The barrier can be achieved by either of the following methods.

Polyethylene method. Prime the slab with an asphalt primer and allow it to dry Apply cold-type, cut-back asphalt mastic with a straight-edged trowel to the entire slab surface. Allow it to dry for 30 minutes. Unroll a 4-mil polyethylene film over the slab, cover the entire area, and overlap the edges by 4 inches. Walk in the film by stepping on every square inch of the floor to ensure proper adhesion. Small bubbles are of no concern.

Two-membrane asphalt felt or building paper method. Prime and apply mastic with a notched trowel (FIG. 3-9) at the rate of 40 square feet per gallon. Let set 2 hours. Roll out 15-pound asphalt felt or building paper and overlap the edges by 4 inches. Butt the ends. Apply another coating of mastic with the notched trowel and roll out a second layer of asphalt felt for building paper. Lay both layers in the same direction, but stagger the overlaps to achieve a more even thickness.

The finish floor will be laid in mastic on the vapor barrier. This method applies only to tongue-and-groove parquet.

Fig. 3-9: Notched trowel for applying mastic

Fig. 3-10: Flooring over a board subflooring


Let’s move on to the installation of hardwood flooring over wood joists. Use exterior plywood or boards of No. 1 or No. 2 common pine or other softwood that is suitable for subfloors over wood joists. If you use ply wood, it must be at least 1/2 inch thick. Lay the panels with the grain of the faces at right angles to the joists and nail every 6 inches along each joist Use appropriate nails for the plywood thickness. Leave a 1/8 inch space between the panels.

For a board subfloor, use only flat, dry, 3/4-inch dressed square-edged boards that are no wider than 6 inches. Lay them diagonally across the joists with a 1 space between the boards to allow for expansion. Don’t use tongue-and-groove boards. Nail to every bearing point with two 8d or 1 Od common nails. All butt joints must rest on bearings.

Mark the location of the joists so that the flooring can be nailed into them. If subfloor boards are used over sleepers or screeds, allow a ½ inch space between boards.

Good nailing is important. It keeps the board rigid and prevents creeping, which is sometimes caused by the shrinkage of the subfloor lumber. Without adequate subfloor nailing, it is impossible to obtain a solid, non-squeaking floor.

Fig. 3-11 Starter line for nailing first strip


Here are instructions for applying strip flooring that is to be laid on plywood-on-slab, screeds, and plywood or board subfloors.

When a plywood or board subfloor is used, start by re-nailing any loose areas and sweeping the subfloor clean. Then cover it with a good grade of 15-pound asphalt felt or building paper and lap 4 inches at the seams to help keep out dust, retard moisture from below, and help pre vent squeaks in dry seasons.

For the best appearance, lay the flooring in the direction of the longest dimension of the room or building — across or at right angles to the joists, as shown in FIG. 3- If a hallway parallels the long dimension of the room, begin the flooring by snapping a chalk line through the center of the hall and work from there into the room. Use a slip-tongue to reverse direction when you complete the hail later.

Fig. 3-12: How initial strip will evenly fit into complete flooring picture.

Fig. 3-13: Cross section of initial strip and molding.

Location and straight alignment of the first course is important. Refer to FIGS. 3-11 through 3-13. Place a strip of flooring 3/4 inch from the starter wall (or leave as much space as will be covered by the base and shoe molding) and put the groove side toward the hail. Mark a point on the subfloor at the edge of the flooring tongue. Do this near both corners of the room and then snap a chalk line between the two points. Nail the first strip with its tongue on this line. The gap between the strip and the wall is needed for expansion space and will be hidden by the shoe mold.

If you’re working with screeds on the slab, you won’t be able to snap a satisfactory chalk line on the loose polyethylene film that has been laid over the screeds. Make the same measurements and stretch a line between the nails at the wall edges. Remove the line after you get the starter board in place.

Lay the first strip along the starting chalk line, tongue out, and drive 8d finish nails at one end of the board near the grooved edge. Drive additional nails at each joist or screed and at the midpoints between joists. Keep the starter strip aligned with the chalk line. Predrilled nail holes will prevent splits. Nail additional boards in the same way to complete the first course.

Refer to FIGS. 3-14 through 3-18. They illustrate the steps for matching, inserting, nailing, and setting nails when you install tongue-and-groove hardwood flooring.

Next, lay out seven or eight loose rows of flooring end to end and in a staggered pattern with the end joints at least 6 inches apart. Find or cut pieces to fit within 1/2 inch of the end wall. Watch your pattern for an even distribution of long and short pieces and to avoid clusters of short boards.

Fit each board snug, groove to tongue, and blind-nail through the tongue according to TABLE 3-1. Refer to FIGS. 3-19 and 3-20 for methods of wedging floor boards tight.

Fig. 3-14 Matching tongue-and-groove flooring.

Fig. 3.15 Nailing tongue-and-groove flooring.

Fig. 3-16 Toe-nailing a flooring nail into the subfloor.

Fig. 3-17 Setting the nail to minimize damage to the hardwood flooring strip.

Fig. 3.18 Cross section of toe-nailed flooring strips

After the second or third course is in place, you can change from a hammer to a power nailer (FIG. 3-21), which is easier to use, does a much better job, and doesn’t require countersinking. The power nailer drives a special barbed fastener, which is fed into the machine like a staple, through the tongue of the floor at the proper angle. Power nailers can be rented from many rental yards or hardwood-flooring suppliers.

When using the power nailer to fasten 3 strip or plank flooring to plywood that has been laid on a slab, be sure to use a 3 cleat. The usual 2-inch cleat may come out of the back of the plywood and prevent the nails from countersinking properly. In all other applications, the 2-inch cleat is preferred.

Table 3-1: Nailing Schedule

Continue across the room. End up on the far wall with the same ¾-inch space allowed on the beginning wall. It may be necessary to rip a strip to fit.

Avoid nailing into a subfloor joint. If the subfloor joint is at right angles to the finish floor, don’t let the ends of the finish floor meet over it.

When nailing directly to screeds (no solid subfloor), nail at all screed intersections and to both screeds where a strip passes over a lapped screed joint. Since flooring ends are tongue-and-groove, all end joints do not need to meet over the screeds. End joints of adjacent strips, however, should not break over the same void between screeds.

Fig. 3-19: Using a pinch bar and wedge to tighten flooring strips.

Fig. 3-20: Another method of keeping boards together, using a wood wedge.

Some long boards may have horizontal bends or sweeps that have resulted from a change in moisture content. A simple lever device (FIG. 3-22) can be made on the job to force such boards into position, as well as to pull up several courses. Once the entire floor is in place, nail the shoe molding to the baseboard, not to the flooring.

Fig. 3-21: Using a power nailer to install strip flooring. Insert illustrates how barbed fastener is installed


Plank flooring is normally made in 3- to 8-inch widths and may have countersunk holes for securing the planks with wood screws (FIG. 3-23). These holes are then filled with wood plugs, which are supplied with the flooring in many cases. Plank flooring is installed in the same manner as strip flooring by alternating courses by widths. Start with the narrowest boards, then the next width, etc., and repeat the pattern.

Fig. 3-22: Job-made lever used for forcing strip flooring boards up tight

Manufacturers’ instructions for fastening the flooring vary and should be followed. The general practice is to blind-nail through the tongue as with conventional strip flooring and then to countersink one or more (depending on the width of the plank) No, 9 or No. 12 screws at each end of each plank and at intervals along the plank to hold it securely. Cover the screws with wood plugs that have been glued into the holes. Take care not to use too many screws because with the plugs in place, they tend to give the flooring a polka-dot appearance.

Be sure the screws are the right length. Use 1 inch if the floor is laid over 3 plywood on a slab. Use 1 to 1 1/4 inches in wood-joist construction or over screeds.

Some manufacturers recommend face nailing in addition to other fasteners. Another practice sometimes recommended is to leave a slight crack, about the thickness of a putty knife, between planks.

Fig. 3-23: Installing wood screws in countersunk holes drilled n plank flooring. Plugs are then inserted over screws


You can also lay a new strip floor over an old floor. In this case, the existing wood floor can serve as a subfloor.

Drive down any raised nails, re-nail loose boards, and replace any warped boards that can’t be leveled. Sweep and clean the floor well, but don’t use water. Remove the thresholds to allow the new flooring to run flush through the doorways. Remove doors and baseboards.

Lay asphalt felt or building paper over the old floor, as discussed earlier. Always install the new floor at right angles to the old floor boards. This method is sometimes the best way to handle an old hardwood floor that is in need of extensive repair.


The styles and types of block and parquet flooring, as well as the recommended procedures for their application, vary somewhat among the different manufacturers. Detailed installation instructions are usually pro vided with the flooring or are available from the manufacturer or distributor.

I’ll cover the installation of parquet, block, herringbone, and similar flooring here and later in this chapter. This section applies only to tongue- and-groove parquet flooring where tongues and grooves are engaged. It doesn’t apply to slat-type or finger-block parquet.

First, lay both blocks and the individual pieces of parquet flooring in mastic to a wood subfloor or over a moisture barrier, as described earlier. Use a cold, cutback asphalt mastic and spread it over the entire area that is to be floored at the rate of 1 gallon per 40 square feet. Use the notched edge of the trowel. Allow the mastic to harden a minimum of 2 hours or up to 48 hours, as directed by the manufacturer. The surface will be solid enough after 12 hours to allow you to snap working lines on it. Use blocks of the flooring as stepping stones to snap lines and begin the installation.

There are two ways to lay out parquet flooring. The most common is with edges of parquet units, and thus the lines they form, square with the walls of the room. The other way is a diagonal pattern, with the lines at a 45-degree angle to the walls.

Fig. 3-24: Working lines for laying b flooring in a square pattern

Let’s learn about the installation of the square pattern first. Never use the walls as a starting line because walls are almost never truly straight. Instead, use a chalk line to snap a starting line about 3 feet or so from the handiest entry door to the room and roughly parallel to the nearest wall. Place this line exactly equal to four or five of the parquet units from the center of the entry doorway

Next find the center point of this baseline and snap another line at an exact 90-degree angle to it from wall to wall. This will become your test line to help keep your pattern straight as the installation proceeds. A quick test for squareness is to measure 4 feet along one line from where they intersect, and 3 feet along the other. The distance between these two points will be 5 feet if the lines are true (FIG. 3-24).

Here’s how to lay a diagonal pattern of parquet block flooring. Mea sure equal distances from one corner of a room along both walls and snap a chalk line between these two points to form the baseline. This pattern need not be at a precise 45-degree angle to the walls in order to appear perfect. A test line should again intersect the center of the baseline at an exact 90-degree angle (FIG. 3-25).

Special patterns also are easy to install. Most exciting parquet patterns can be laid out with the two working lines that were just covered. Her ringbone will require two test lines, however. One will be the 90-degree line already discussed. The other line should cross the same intersection of lines, but at a 45-degree angle to both (FIG. 3-25).

Fig. 3-25: Working lines for laying block flooring in a diagonal pattern

If such elaborate, preliminary layout preparation seems a bit over done, keep in mind that it is wood you are installing. Each piece must be carefully aligned with all its neighbors. Small variations in size, which are natural to wood, must be accommodated during installation to keep the overall pattern squared up. You cannot correct a creeping pattern after it develops. A carefully laid-out floor causes less problems.

Wood parquet must always be installed in a pyramid or stair-step sequence, rather than in rows. This method again prevents the small inaccuracies of size that are found in all wood flooring from magnifying or creeping until the pieces look misaligned.

Place the first parquet unit carefully at the intersection of the base and test lines. Lay the next units along the line ahead and to the right of the first ones. Then continue the stair-step sequence. Carefully watch the corner alignment of new units with those that are already in place. Install in a quadrant of the room. Leave the trimming at the walls until later. Then return to the base and test lines and lay another quadrant, again repeating the stair-step sequence. Cover this area with the flooring. Work backwards from the baseline toward the door. A reducer strip may be needed at the doorway

Most wood floor mastics, regardless of the type or open time, will allow the tiles to slip or skid when sidewise pressure is applied for some time after the open time has elapsed. By working from knee boards or plywood panels that have been laid on top of the installed area of flooring, you can avoid this sidewise pressure. For the same reason, no heavy furniture or activity should be allowed on the finished parquet floor for about 24 hours. Some mastics must also be rolled.

Cut blocks or parquet flooring pieces to fit at the walls. Allow a 3/4 expansion space on all sides. Use cork blocking in 3-inch lengths between the flooring edge and the wall to permit the flooring to expand and contract (FIG. 3-26).

With blocks, a diagonal pattern is recommended in corridors and in rooms where the length is more than 1 1/2 times the width. This diagonal placement minimizes expansion under high humidity conditions.


Every do-it-yourselfer would prefer typical installations that have no handicaps or problems to overcome. Life doesn’t seem to work this way, however. Here are instructions on how to solve special hardwood- flooring installation problems.

Oak flooring over a radiant-heated concrete slab Flooring will not impair the efficiency of the heating system, but slightly higher water temperatures may be required. An outside thermostat is therefore recommended to anticipate rapid temperature changes. Boiler water temperature must be controlled to keep it to a maximum of 25 degrees Fahrenheit and so limit the temperature of the slab surface to about 85 degrees, which is an acceptable level for most mastics.

The flooring should be installed as in any other slab project, except do not fasten the plywood to the concrete with either nails or powder-actuated fasteners. Turn on the heating system at least 48 hours before the flooring is delivered to the job because the heat will drive remaining moisture out of the slab. Allow the flooring to become acclimated to the environment for 2 or 3 days, then install by the recommended slab methods covered earlier in this chapter. Remember to check the flooring and mastic manufacturers’ specifications for suitability for use over radiant heat.

Strip flooring in a wood plenum system. This method of housing construction utilizes a crawl space that is completely sealed to the outside as a plenum to which air from the heating/cooling system is supplied. The air then enters each room through floor ducts.

A ground cover of polyethylene film is essential. The heating system must also operate for at least 48 hours prior to the delivery of the flooring in order to stabilize the moisture condition. No other special considerations are necessary to install the flooring.


Hardwood flooring is popular for school gyms, athletic clubs, and home fitness rooms Gymnasium floor products are often made of 3 pecan or maple. Beach and oak are also suitable. It is most important to have some resiliency built into these floors. In most respects, however, installation closely follows the screeds-in-mastic method, which is recommended for conventional use, with a plywood or board subfloor installed over the screeds.

Make sure the slab is dry and level with a good float finish. Maximum surface variation is 1 inch in 10 feet. Grind down high areas and fill low areas with a concrete leveling compound.

Sweep the slab clean and prime with asphalt primer. Let dry thoroughly and coat with asphalt mastic. Use a notched trowel and apply at a rate of 40 square feet per gallon. Embed a layer of 15-pound asphalt felt or building paper. Start at a wall with a half sheet and lap seams. Cover this with another layer of mastic and embed a second layer of asphalt felt or building paper. Start at the same wall with a full sheet to cover the seams of the first layer.

Either hot or cold mastic is satisfactory. If the cold type is used, be sure to allow 2 hours for the solvents to evaporate before you apply the building paper.

An alternate method of surface damp-proofing is to embed a 6-mil polyethylene film in a cold mastic, as described earlier. Lap the film edges 6 inches.

A suspended concrete slab needs no surface damp-proofing. Cross- ventilation below the slab is essential, however, and if the slab is suspended over exposed earth, a ground covering of 6-mil polyethylene should be provided.

Screeds used in this application are identical to that previously described, with the following exceptions. Place them on 12-inch centers. If a subfloor is used, 16-inch centers are allowed. Leave a 2-inch space between the ends of the screeds and the base plate on all walls to allow for expansion.

The finish flooring may be nailed directly to the screeds. A much more sound and satisfactory floor can be achieved, however, by installing a subfloor of a minimum of 3/4 plywood or 3/4 dressed square-edged boards that are no wider than 6 inches.

Follow the arrangement and nailing schedules described previously. If boards are used, leave a ½ inch space between them.

Start laying the finish flooring in the middle of the room and work toward the walls. Place the first two courses groove to groove and use a slip-tongue joint to join the strips. Face-nail as well as blind-nail both courses. Proceed with succeeding courses in the conventional manner. Use either 7d or 8d cut steel nails, screw-type nails, or 2-inch barbed fasteners.

After an area 3 to 4 feet wide has been laid across the room, leave a 1 expansion space between the last course laid and the next course (FIG. 3-27). Repeat the expansion space evenly at 3- to 4-foot intervals across the room.

Fig. 3-27: Use of metal washers to provide expansion space on a gym floor.

Nailing is most important. Nail to all screeds and to both screeds when a strip passes over a lapped screed joint. All end joints do not need to meet over screeds, but adjoining strips should not break over the same screed space. If a subfloor is used, nails must be no more than 10 to 12 inches apart.

Allow a 2-inch expansion space along all walls and doorways. The space can be covered at the walls with an angle iron that is bolted to the wall or a special wood molding, and at the doorways by a metal plate that is designed for such use.


The National Oak Flooring Manufacturers’ Association recommends a number of tips for easier and better flooring installation.

Work from left to right. When laying strip flooring, you’ll find it easier to work from your left to your right. Left is determined when your back is to the wall where the starting course is laid. When it is necessary to cut a strip to fit to the right wall, use a strip that is long enough for the cutoff piece to be 8 inches or longer. Start the next course on the left wall with this piece.

Save short pieces for closets. For best appearances, always use long flooring strips at entrances and doorways. Save some of the short pieces for closet areas and scatter the rest evenly in the general floor area.

Put a frame around an obstruction. You can give a much more professional and finished look to a strip-flooring installation if you frame hearths and other obstructions and use mitered joints at the corners.

Reverse the direction of strip flooring. Sometimes it’s necessary to reverse the direction of the flooring to extend it into a closet or hallway. To do this, join the groove edges, with a slip-tongue that is available from flooring distributors. Nail it in place in the conventional manner.

Use only sound, straight boards for subfloors. The quality of the sub-flooring will affect the finish flooring. Use only square-edged, 3/4 dressed boards that are no wider than 6 inches. Boards that have been used for concrete form work are often warped and damp and should not be used.

Don’t pour concrete after the flooring is installed. Concrete basement floors are sometimes poured after hardwood flooring has been installed. Many gallons of water from the drying concrete evaporate into the atmosphere of the house, however, where it may be absorbed by hardwood flooring and other wood components. This is not a recommended building practice since excessive moisture will cause problems with wood floors and other woodwork. Wood flooring should not be installed until after all concrete and plaster work is completed and dry.

Put the voids between the screeds to good use. Masonry insulation fill, which is normally used in hollow concrete blocks, can be poured between the screeds or sleepers of a slab installation to give additional moisture protection and deaden the drumming sound that sometimes occurs from foot traffic.

Deaden sound in a multi-story building. Noise transmission from an upper to a lower floor can be reduced in the following way Nail the sub- floor to the joists in the normal manner and then cover it with 1/2-inch or thicker cork or insulation board that has been laid in mastic. Cover this with another 3/4 plywood subfloor, which has been laid in mastic. Nail the finish strip or plank floor to the plywood, or lay block or parquet flooring in mastic on the plywood. In the case of parquet, the second sub- floor plywood can be a 1/2-inch tongue-and-groove type. Note that specifications for some high-rise apartment buildings call for other types of sound-deadening construction and should be followed.


As mentioned earlier, there are numerous ways of installing a satisfactory hardwood floor. Thus far, in this chapter you’ve learned about the more traditional methods. Another method is called the floating floor system.

Figures 3-28 and 3-29 illustrate a cross section of a floating floor installation over wood for suspended concrete with a foam underlayment. If the subfloor is in contact with the ground, or on-grade, a 6-mil polyethylene film barrier should first be installed over the subfloor and the foam applied over the poly film (FIGS. 3-30 and 3-31). Lap the seams of poly film at least 8 inches. If the subfloor is not level to within 3/16 inch in a 10-foot radius, it should be leveled with a latex leveling compound.

Fig. 3-28: Cross section of floating floor installation of (1) plank, (2) foam underlayment, and (3) plywood subfloor.

Fig. 3-29: Floating floor over wood or suspended concrete.

Fig. 3-30: Cross section of floating floor installation of (1) plank, (2) foam underlayment, (3) poly film, and (4) concrete.

Fig. 3-31: Floating floor over concrete on-grade.

Tools required for a floating installation include a hammer, a hand or power saw, wood, plastic, or equivalent 1/2 spaced wedges, crowbar, a chalk line, installation adhesive, an upping cover block, and any special tools.

Once the poly film, if it is used, and the foam underlayment have been installed over the subfloor, the job site is ready for the boards. Don’t open the bundles until you are ready to begin the installation process. Decide which direction the boards will run. Start at one side wall (FIG. 3-32) with the first row of boards. Allow a ½ inch expansion along the side and end walls (FIG. 3-33) by using wood or plastic wedges, or equivalent spacers. If the starting wall is out of square, it is recommended that the first row of boards be scribed to allow for 1/2 inch of expansion (FIG. 3-34) and a straight working line.

Fig. 3-32 Start at one sidewall

Fig. 3-33 Use wedges to establish expansion space

Fig. 3-34 Scribing boards

Fig. 3-35 Applying adhesive along side grooves

Fig. 3-36 Applying adhesive on end joint

The specially milled boards must be edge- and end-glued using the manufacturers’ adhesive or equivalent. Apply the adhesive in 8-inch long beads with a 12-inch space between the beads (FIG. 3-35) along the side grooves. Fully glue every end joint (FIG. 3-36). If any excess glue squeezes out on to the finish surface, wipe it off with a moist cloth.

Install the first row. Use the appropriate expansion space and face the grooved side toward the wall (FIG. 3-37). The subsequent rows are installed and edge- and end-glued with a hammer (FIG. 3-38) and tapping block to prevent damage to the protruding tongue. Check for a tight fit on the sides and ends. Stagger 2 feet between the end joints of adjacent board rows (FIG. 3-39).

Most often, the last row does not fit in width. When this occurs, follow this simple procedure. Lay a row of unglued boards with the tongued side toward the wall, directly on top of the last installed row (FIG. 3-40). Lice a short piece of the strip and put it against the wall. Moving down the wall, draw a line with a pencil along the row. The resulting line gives the proper width for the last row which, when cut (FIG. 3-41), can then be wedged into place using a crowbar and cover board (FIG. 3-42) to prevent damage to finished walls or molding.

Fig. 3-31: Installing first row

Fig. 3-38: Installing subsequent rows with a hammer and block

Fig. 3-39: Check for tight fit of boards

Fig. 3-40: To make last row fit in width: first, lay a row of boards on top of the last install row

Fig. 3-41: Cut the board on the scribed line

Fig. 3-42 Wedge the last row of boards into place with a crow bar

Fig. 3-43: Attach trim to the wall, not the flooring

Make sure that wedges or spacers are removed when the installation is complete. The expansion space should also be covered with an appropriate molding that allows the boards to move freely underneath. Always attach the trim to the wall or vertical object (FIG. 3-43) and never to the floor boards.

One more note: in large areas that measure more than 24 linear feet, use a ¼ inch expansion for each 12-linear feet of width and length.


General installation methods for plank flooring were covered earlier in this chapter. Here’s another popular method.

Fig. 3-44: Cross section of a plank-flooring installation

Suggested tools and accessories include a conventional claw hammer or power nailer and a No. 80, 3/4 counterbore, unless the flooring is pre-bored at the factory. You’ll also need 7d, 2 ¼ inch screw-type flooring nails for conventional nailing or power cleats for power nailing. No. 9, 1 ¼ inch flathead wood screws and walnut or oak wooden plugs, 5/16 x 3 in diameter, should be used.

Figure 3-44 illustrates a cross section of a plank flooring installation, including the subflooring. Kiln-dried coniferous lumber, which is 1 x 4 inch to 6 inch wide, square-edged, and laid diagonally over 16-inch, on- center wood joists, is recommended A minimum of 1/2 thick exterior plywood can also be used with the long edges at right angles to the joists and staggered so that the end joists on adjacent panels break over different joists. Particleboard is not considered a suitable subfloor.

Refer to FIGS. 3-45 through 3-48. Lay out your plank flooring only after the plasterboard and tile work have thoroughly dried and all but the final woodwork and trim have been completed. The building interior should have been dried and seasoned and a comfortable working temperature should exist during the plank flooring installation.

Make sure that the subfloor is adequate and properly nailed before you start. Clean the subfloor surface and cover it with 15- or 30-pound asphalt saturated felt. Lap the edges at least 4 inches. Double the felt around the heat ducts in the floor.

Fig. 3-45 Installation details of plank flooring

Fig. 3-46: Using spacers between plank flooring

Fig. 3-47: Installation of wood screw and plug to fasten plank flooring

Fig. 3-48: The finished plank floor

Plank flooring should be laid at right angles to the floor joists and, if possible, in the direction of the longest dimension of the room. Begin laying tongue-and-groove plank flooring in a room corner with the edge groove of the planks facing the wall. Provide no less than a 3/4 expansion space or what will be covered by the baseboard and trim.

The first run of planks should be face-nailed and then countersunk. All other runs should be nailed at a 50-degree angle on S-inch centers at the tongue. Make sure the end joints are staggered. Remember to leave a small space between the planks — usually 1/32 inch is sufficient.

After nail installation of the plank flooring, bore appropriate holes for screws and plugs. Use the counterbore if the flooring was not factory bored or if additional boring is desired. Screws and plugs should be located at the ends of each plank and at intervals frequent enough to hold the planks securely. Whenever possible, screws should extend into the joists. The number of screws to use is a function of job conditions and the desired surface appearance. Use one screw and plug on each end of 3- and 4-inch wide planks, two widthwise on the ends of 5- and 6-inch planks, and three widthwise on the ends of 7- and 8-inch planks.

How to sand and finish your plank flooring will be covered in the next section.


One of the easiest and most beautiful floorings you can install is the parquet floor (FIG. 3-49). Early parquet floors were extremely difficult to install correctly but modern manufacturing and application techniques have placed parquet flooring within the can-do realm of the typical do-it yourselfer.

Prepare the subfloor in the same manner as for other types of hard wood flooring. Make sure it’s nailed down tightly, clean, and level. If you’ve stripped an old floor off to install your parquet flooring, make sure the mastic and fasteners are gone. Old wood should be thoroughly sanded with 3 1/2 open-grit paper to remove oils, waxes, paints, varnishes, glues, and other foreign matter. After sanding, the subfloor should be swept and vacuumed to remove dirt. An alternate method is to cover the existing subfloor with ½ inch plywood.

Figure 3-50 shows the proper method of laying out the room prior to installation and the proper procedure to follow in laying the parquet blocks. Locate the center of the room by measuring from the center of the length and width sides with a chalk line. Then determine the number of parquet blocks that are to be laid from the center of the room to the wall.

Fig. 3-49: Parquet block flooring is actually easy to install

If the measurement leaves less than 2 inches of block next to the wall, shift the centerline to allow 2 inches or more of the block to be laid at the wall. Be sure that at least 1/2 inch or more of an expansion space is left around all four walls. Following installation, cover the expansion area with baseboard or quarter round.

Spread the adhesive according to label instructions. Lay a quadrant of the room from the centerline with blocks. Complete that area before you start the next. The accurate alignment of the first 10 blocks is most important. Never force or tap blocks with a hammer. Just tightly lift the tongue- and-groove blocks by hand. Be sure that corners form right angles and match properly at points A and B in FIG. 3-50.

Fig. 3-50: Laying out a parquet block floor.


Adhesive is used in most hardwood flooring installations. It is especially critical to the installation of parquet block flooring.

Spread the adhesive on the floor with a notched trowel. Apply the adhesive to an area of such size that the flooring can be laid into the adhesive within approximately 2 hours. Don’t let a heavy skin form on the adhesive. A light skin on the adhesive can easily be broken by pressing the flooring into it.

After you spread the adhesive, wait to install the flooring. Leave the adhesive open to help ensure a faster bond. Allow 20 to 30 minutes for bonding, depending on the temperature and humidity.

To install the flooring, press down firmly Lift a piece of flooring occasionally to be sure the adhesive is transferring to the block. Remember that wood flooring needs expansion space around its edges.

Once the installation is complete, some adhesives require that you roll the floor carefully in both directions with a 75 to 100 pound roller.

To remove adhesive from tools, use naptha, white gas, or mineral spirits. Be careful not to get it on a surface it could damage.

Your hardwood floor is installed! Congratulations. The work isn’t over, though. The final step in the installation of a hardwood floor is the finishing, which includes sanding and then applying one of the many types of finishes that will bring out the wood’s natural beauty while protecting it from wear.

Prev.: Planning a Hardwood Floor
Next: Finishing hardwood floors

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Wednesday, 2020-04-29 12:53