Interior TRANSITIONS--PLANAR

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INTRODUCTION

In addition to the transition between different architectural planes in an interior space discussed in Section 10, there are also transitions between different materials, finishes, or levels in the same plane, including partitions, floors, and ceilings. These planar transitions are necessary to physically join different construction elements and resolve other functional requirements, but they can also contribute to the overall design concept.

As space dividers, walls and partitions serve the obvious functional purposes of visual and acoustical separation, security, and control of movement. Beyond this, however, they are one of the prime determinates in de fining the character of interior space. Planar transitions provide design opportunities to differentiate materials, emphasize areas, modify scale, modulate space, and create visual interest.

PARTITION TO PARTITION

As discussed here, partitions both divide and create space as vertical barriers and can be treated and detailed in many ways. When two or more finish materials or construction elements join, the resulting transition must be detailed. This can be done so that the partition surfaces are in line with each other or slightly offset. There are nine basic ways these transitions can be made.

The type of partition transition that the designer selects is usually coordinated with the base or ceiling treatment, but it doesn't have to be. E.g., a vertical reveal between sections of a partition may be combined with a reveal transition between the partition and the ceiling. Alternately, vertical corners could be created with 90-degree angles while ceilings could consist of curved forms.

--- Partition-to-partition transition concepts: in plane; plain offset; interrupted offset

--- In-plane partition transitions: (a) butt joint--A butt joint minimizes the effect of the material transition and places more emphasis on the entire plane of the partition. Butt joints are typically used where the adjoining materials are identical.

(b) reveal--A reveal joint provides a distinct separation between materials and conceals any minor imperfections in alignment. Reveal joints also provide a good separation between different materials or finishes.

These joints also make it easy to remove one portion of the partition for repair or replacement without disturbing adjacent panels.

(c) batten--Batten joints are easy to construct and cover any imperfections in the edges or alignment of the surfaces underneath. Battens can be prefinished and when applied, give a neat, crisp edge to the materials.

In-Plane Transitions

BUTT JOINT

The simplest transition is a basic butt joint. In this detail the same substrate material is used and the finishes are joined in a straight, vertical line. Examples of this type of joint include two different adjacent paint colors, a vertical seam in vinyl wallcovering, or two wood panels touching along their vertical edges.

Butt joints provide a smooth, uniform appearance to a partition if that is the design intent.

They are simple to construct and inexpensive and are necessary for most panelized materials such as wood or stone. However, some materials, such as wallpaper or vinyl wallcovering may peel at the joint or two materials may shrink, causing an unsightly gap and defeating the design goal of a plain, uniform surface finish. The designer must choose to minimize the effect of a joint with a butt joint or celebrate it with one of the other transitions discussed in this section.

One variation of a butt joint is a butt joint with eased edge. An eased edge is a slight beveling of the edge of a material, generally a fraction of the total thickness, so the visible edge is not at a ninety-degree angle. E.g., a wood panel can be given a 1/16 in. (1.6 mm) bevel. Although this shows the joint a little more, it’s effective in concealing any slight, uneven shrinkage of the panels because the beveling was intentional.

REVEAL

Reveals are obvious separations between two materials with a joint that has an obvious depth to it. As discussed here, reveals are useful for concealing minor imperfections in joint width or alignment of adjacent surfaces. They also make painting or other finishing of different adjacent materials easier. Some of the ways reveals can be created.

--- Plain offset partition transitions: (a) sharp edge Sharp edge wall transitions are the most common and simplest and least expensive to construct. They are what most people expect to see. Partition molding can easily be cut and fit to these types of transitions. (b) chamfer Chamfered corners soften the look of the corner and provide a safer edge. Both inside and outside corners shown here are chamfered, but typically only outside corners are chamfered. (c) rounded: Rounded transitions soften the corners even more than chamfered corners and deemphasize the change in plane. Rounded corners are also safer than square corners. As with chamfering, only the outside corners may be rounded, while inside corners can remain squared off.

BATTEN

A batten joint is one that is covered with another material extending from the face of two

finished surfaces that are in the same plane. A batten may be the same material as the surfaces, such as wood, or a different material, such as metal over stone panels.

In most cases, the batten is narrow relative to the exposed finished surfaces, but it may be as wide as the designer determines.

Battens are an easy, effective way to conceal joints because the finish materials don’t have to be installed with their edges perfectly plumb or aligned. The batten hides minor imperfections. Because battens emphasize the joints, their locations should be carefully considered, in relation both to each other and to horizontal details. Battens are especially effective with wood detailing, coordinated with applied base and ceiling trim.

The method of attaching battens to the substrate should also be carefully considered. The connection may be concealed with adhesives or clips, or may be emphasized, with exposed screw heads, bolt covers, or other visible fasteners.

--- Methods of forming chamfers 3/4" (19) approx. 4" (100) with 2-1/2" studs approx. 3-1/2" (90) (c) chamfer with metal studs (d) wallboard chamfer-small studs approx. 2-3/4" (70) with 2-1/2" studs wood blocking 1-5/8" (41) studs 2" x 2" 38 x 38) stud 2" x 4" (38 x 89) stud wood blocking (a) standard chamfer trim (b) fire-rated chamfer (e) chamfer with wood studs ---

Plain Offsets

Offsets are used where two adjacent wall surfaces are not aligned, for aesthetic reasons, for functional reasons, or both. E.g., one portion of an otherwise flat wall may need to be built out a few inches to conceal mechanical services or one portion of a wall may be recessed to highlight a large piece of art. Unlike outside corners of adjacent rooms that may extend for several feet or more, partition offsets are out of plane by only a few inches. The difference is that an offset is perceived as being part of the same partition plane, while an outside corner is clearly perceived as the inside corner of an adjacent space. Offsets can be treated in several ways, three of which are simple in their appearance and detailing and three of which show an obviously interrupted change at the outside and inside of the offset.

SHARP EDGE

A sharp edge offset is simply a 90-degree change in wall surface, as diagrammed.

This is a standard partition corner with the finish material, base, and any ceiling trim following the line of the partition. The offset may also be made with an angle other than 90 degrees.

This detail provides the minimal amount of emphasis to the change in plane. However, if the offset is small, it may be difficult to construct it with some materials, such as wood paneling or propriety metal panels because these materials are sometimes difficult to fabricate in narrow pieces.

CHAMFER

A chamfer is a corner built with a slight angle as a transition between two other planes. Most commonly, a 45-degree chamfer is built between two planes at 90-degree angles to each other.

In contrast with an angled offset, chamfers are small in relation to the height and area of the wall surfaces, most often in the range of a fraction of an inch to a few inches (approximately 15 mm to 100 mm).

Chamfers can be used to visually soften what would otherwise be a sharp angle and to minimize the sharp edge if safety is a concern. For gypsum wallboard partitions chamfers can be easily formed with proprietary aluminum trim pieces. Refer to manufacturers of chamfer trim. However, premanufactured bevel trim usually requires that the wallboard be held back from the corner, so if fire-rating or acoustical performance is important, it may be necessary to use two layers of wallboard.

There also may not be a corresponding premanufactured inside corner bevel, so small in side bevels would have to be framed with wood and finished with joint compound. For larger chamfers, an outside corner needs to be framed with wood.

For materials other than gypsum wallboard, the ease with which small chamfers can be detailed depends on the type of material. Wood is easy to form at an angle, but creating chamfers with some types of thick stone may be problematic.

ROUNDED

Like chamfers, rounded corner offsets are usually small relative the height and area of the wall planes. With gypsum wallboard, both outside and inside corners can be formed with proprietary aluminum trim. These trim pieces are available in radii from 5/8 in. (10 mm) to 6 in. (152 mm), depending on the manufacturer. Larger corners must be formed with curved wallboard or other means.

Although corners can be curved by various means, installing curved base, cornice molding, or chair molding can be problematic. Resilient straight base can be curved easily, but cove base is limited in the smallest radius that it can be curved without distorting. Wood base and other wood moldings can be curved using various means, such as lamination, machining to radius, segmenting, or steam bending, but these methods are sometimes difficult and more expensive than installing straight wood base.

---Interrupted offset partition transitions (a) reentrant (b) trimmed Reentrant corners have a small notch at the corner and are used to add visual interest and emphasis to an otherwise plain 90-degree corner. They may be used on inside corners, as shown here, but they are typically used on outside corners.

Trimmed corners also provide emphasis to a change in plane. They can also be used to conceal changes in material at the corner or hide irregularities in the joint. Trimmed corners are often used in conjunction with other trim molding.

Overlaps can be used to break up an otherwise long partition or to provide a more dynamic sense of enclosure to a space. Concealed lighting can be added to highlight one partition. (c) overlap

--- Reentrant corners (c) inside reentrant corner (d) reentrant formed with trim (a) outside reentrant (b) double reentrant ----

Interrupted Offsets

Interrupted offsets are those planar offsets that have a signi ficant piece of construction where the planes change direction. As shown, there are three basic types of these offsets.

RE-ENTRANT

A reentrant offset has an inside notch at the corner. These can occur at an outside corner as well as an inside corner, although their use is most often limited to outside corners. Reentrant corners are used to soften the abrupt turn of plane as well as to add emphasis and visual interest to the corner. For most types of reentrant corners, the primary partition construction of studs and gypsum wallboard cannot easily be formed into the reentrant shape and would leave an unusual shape on the opposite side of the partition.

The shape itself must be formed with trim or other applied materials. Some of the ways of doing this are shown.

However, larger reentrant corners may be formed by building a standard partition and building the reentrant shape with furring or added studs.

TRIMMED

Trimmed corners have an applied material on outside or inside corners that extends out from the finish surface of the partition. Trimmed corners are used to conceal irregularities in the joint between adjoining planes, to make a transition from one finish material to another, or simply to emphasize the corner for aesthetic reasons.

There may or may not be a flat surface between the trims depending on the amount of offset. Applied trim corners are generally easy to build as the basic partition is constructed and then trim material applied by whatever means is appropriate.

OVERLAP

Overlapped partition transitions create an effect of one partition sliding past another without the connection being visible. These types of transitions can be used to create the effect of floating partitions, to modulate the scale of large expanses of walls, or to create a three-dimensional vertical plane. Functionally, they can also be used to conceal small open storage areas or to provide a space for indirect side lighting.

In addition to overlapping in just one place, an entire wall plane can be modulated in and out with multiple overlaps. The concept of overlapping partitions can be combined with the modulated barrier type discussed in Section 5.

Overlaps are easy to construct as one partition is simply extended past another. Base molding and other finishes are also easy to apply. As variations on this concept, the overlap can be curved or angled to suit the design requirements. The only limitation is that there must be enough distance between the partition planes to allow workers to apply finishes and moldings to the inside of the small space created.

FLOOR TO FLOOR

Floors are major design elements in interior spaces. They can be simple, single-plane functional surfaces or they can be raised or lowered to de fine space or set certain areas apart for speci fic functions. Levels can be varied to create dynamic spaces separated into visually distinct areas without the use of wall planes. Floor-level changes also create a strong sense of "here" and "there" within the same volume.

Floors direct movement horizontally as well as vertically. Changes in floor planes without steps or ramps automatically control and direct horizontal circulation without closing off space. The location and use of stairs or ramps determines the position and type of experience of moving from one plane to another. That experience can be purely functional or it can be made monumental, gradual, deliberate, or exciting to suit the design requirements of the space.

Floors are one of the few building elements that people actually touch. Therefore, the tactile qualities of the flooring and the transition from one floor to another can be a powerful tool for the designer to enhance the experience of a space.

Floors can also affect acoustic qualities by reflecting or absorbing room sounds and by absorbing or emphasizing the footfalls of people walking. This in itself can greatly in fluence people's perception of the size of a space as well as its liveliness, formality, and function.

Noisy spaces, E.g., generally seem more dynamic and exciting, while quiet spaces suggest formality.

Because most interior design involves working within existing buildings or with buildings that have already been designed and are under construction, most floor-level changes involve building up from a structural floor. Depending on the architectural limitations of the space or the existing ceiling height, the amount of floor level change that the interior designer may make can be limited. However, even minor changes can strongly enhance the interior design concept.

Floors transition to other floors in one of two ways, either in the same plane or in different planes. The various ways floor-to- floor transitions can be made. There are three basic types of transitions: in plane, plain offset, and interrupted offset. Refer to a discussion of the ground plane as a design element in itself.

---- Floor-to- floor transitions in plane: plain offset; interrupted offset; interrupted offset; (handrails not shown for clarity).

--- In-plane floor transitions (a) abutting materials (b) protective edge (c) transition strip.

Two materials can be butt-joined if they are approximately the same thickness and are self-edging. This detail minimizes the emphasis given to the joint. However, if one material is slightly higher than the other, damage may occur.

Using a metal angle, plastic edging, or similar protective edge prevents damage to both materials and can accommodate minor differences in height while minimizing the appearance of the joint.

A transition strip highlights the change in floor materials and can accommodate larger differences in material height while maintaining accessibility. The transition strip can be the same material as one of the floor surfaces or it can be a contrasting material.

---

In-Plane Transitions

In-plane transitions are those in which adjacent finishes are flush with each other or within 1/2 in. (13 mm) or each other. The planes must be within this distance to conform to accessibility regulations. Changes greater than this must be made with a ramp. There are three basic ways these types of transitions are made.

ABUTTING MATERIALS

The simplest same-plane transition detail is butting two materials together. They are placed in direct contact with each other. This is the simplest transition to make and may work well for some materials if they are perfectly flush with each other.

However, without additional protection, some materials may be damaged along the edge as people walk across the joint. E.g., a hard surface material like wood or stone may become chipped if installed slightly above another material such as carpet.

This type of flooring installation is used when the materials must change for functional reasons, but the designer does not want to emphasize or call attention to the change.

PROTECTIVE EDGE

To avoid the potential damage to materials, a thin protective edge should be placed between the materials, flush with the highest installed material. This is most commonly done with a metal edge angle. This type of detail provides protections for the edge and minimizes maintenance issues while still minimizing the joint and transition. Carpet and tile accessory manufacturers provide a wide variety of edge strips for their respective materials to transition to other materials.

TRANSITION STRIP

A transition strip is a material placed between two adjacent floor surfaces both to protect the edges of the two materials and to highlight or emphasize the transition. A transition strip can also be used to make minor changes in the finish elevation of the two surfaces. This is a practical safety feature to prevent tripping as well as being required for accessibility. Any change in elevation up to 1/2 in. (6 mm) must be made with a slope no greater than 1:2; that is, a 1/4 in (6.4 mm) high slope would need a horizontal run of 1/2 in. (13 mm). Changes in elevation up to 1/4 in. (6.4 mm) can be made vertical.

--- Floor transition details (a) protective edge angles (b) height transition (c) contrasting transition material.

The designer also has the choice of placing an intermediate material to emphasize the transition or to make up for minor differences in level. The intermediate material can be the same as one of the flooring materials or a third, contrasting material can be used.

-- Interrupted offset floor transitions: (a) visible plane change (b) concealed plane change (c) functional transition (d) floor as bench or platform The floor surfaces and the change in elevation of a visible plane change can be clearly seen from both the lower and upper levels. If a guard is needed it should be as open as possible while still meeting building code requirements.

A concealed plane change looks like a low partition when viewed from the lower level. It’s a simple, low-cost method of minimizing the appearance of the level change while providing a guard. The solid partition also hides furniture and other equipment placed against the wall.

Like a concealed plane change, a functional transition provides usable area along the level change. Functions such as storage, counter space, seating, and display space can be built into the transition.

Using the upper level as a platform provides a visible plane change while making use of the edge. If the applicable building code does not require a guard, accessories along the edge can provide a visual cue for a moderate amount of safety.

----

Plain Offset Floors

When adjacent floors are on different levels, one of two conditions is possible: either there is provision for convenient movement between levels at any location or the two floors are separated so that movement is possible only at selected locations.

Plain offset floors use either stairs or ramps, or both, to make the transition between levels.

In these types of level transitions, the stair or ramp is the main design feature and continues across a wide portion of the level change, serving as both the method of making the transition and the physical means of movement. In most cases, when stairs are provided, an adjoining ramp is required for accessibility. Ramps cannot have a slope greater than 1 vertical unit for every 12 horizontal units, or 8.33%.

Refer to Section 8 for more information on the design and detailing of stairs and ramps.

PLANE CHANGE WITH STAIRS

Stairs can be used where the difference between floor levels is greater than about 12 in. (305 mm). This is because at least two steps should be used for safety; single steps should be avoided whenever possible. Stairs can occupy the majority of an opening with a minimal ramp provided only for accessibility. Handrails must be provided as required by the applicable building code.

PLANE CHANGE WITH RAMP

Ramps are best used for movement where the difference between the floor levels is less than about 12 in. (305 mm) because of the safety issues with single steps. Ramps can be used alone or with a stairway. Ramps allow for barrier-free design and generally create less of an impediment to the smooth flow of circulation. A ramp can occupy the majority of an opening with a stair of minimal width for those who prefer stairs or who cannot use ramps.

Interrupted Offset

Interrupted offsets occur when the majority of the level change is blocked to prevent movement up and down. Of course, at a selected location there is a stair and ramp to allow for physical movement between levels, but in this concept this is a minor part of the level transition. There are four basic methods for designing and detailing interrupted offsets: visible plane changes, concealed plane changes, functional transitions, and transitions in which the upper level becomes a usable surface.

VISIBLE PLANE CHANGE

A visible plane change occurs when occupants can see both the lower and upper levels. If a guard is needed, it’s open so there is a clear sight line. Visible plane changes are used when the space must be kept as open as possible and when the designer wants to emphasize the change. The IBC does not require a guard if the change in level is less than 30 in. (762 mm), but for safety reasons a guard should be used. For a completely open feeling a glass guard can be used. One way to detail this is shown.

CONCEALED PLANE CHANGE

A concealed plane change uses a solid railing to limit the view from the lower level. This is used when the level change needs to be deemphasized or when there is furniture or other equipment near the edge. The simplest method of creating this type of concealment is to use a low partition, continuing the finish material of the level drop up the surface of the partition.

The partition can be capped in any of the ways shown.

FUNCTIONAL TRANSITION

A functional transition incorporates useful elements into the change in level. E.g., storage units face the lower level and built-in seating is located at the upper level. This conceptual approach minimizes the effect of the level change, making it look more like a low partition, if this is the design intent. Whatever functional element is used also serves as a guard for safety.

FLOOR AS BENCH

The upper level of a floor transition can also be used as a bench or other type of work surface. This maintains the open feeling of the space while providing an indication of a level change, providing some degree of safety if a guard is not otherwise needed by the applicable building code.

--- Glass guard and level change: as required by floor structure and design 42" (1067) min. blocking as required carpet or other floor finish carpet or other floor finish glass railing molding, bolt to steel angle steel angle lag screwed to framing metal or wood handrail metal finish or other finish as designed tempered glass.

--- Ceiling-to-ceiling transition concepts: in-plane transitions in plane transition offset transitions offset transitions.

CEILING TO CEILING

As discussed here, the ceiling is a major design element because it’s always in view and occupies a major percentage of the total planar elements that de fine a space. Because the ceiling must also contain a variety of other features such as lighting and mechanical equipment, its design is important.

A ceiling can express the structure of a building or completely conceal it with a suspended flat surface. Alternately, a ceiling can create an entirely new shape. If sufficient space is available, ceilings allow a great deal of flexibility in shaping space because they don’t have to be flat or follow a particular con figuration like floor and wall planes do.

Because ceilings are nearly always out of physical reach, their effect must be a purely visual one. The type of material used for the ceilings and the amount of space above the ceiling determines what type of transition may be most appropriate.

There are basically two variations of transition from one ceiling to another: transitions that are in the same plane and transitions that are offset.

--- In-plane ceiling transitions (a) abutting (b) transition strip (c) reveal (d) feature strip.

Butt joints provide a good in-plane match of finish materials if both finishes are placed on the same substrate or both substrates are the same thickness. These types of joints are simple and easy to make, but it’s difficult to get two surfaces to align if they are on different substrates.

Transition strips can accommodate slightly different substrate thicknesses and disguise any minor problems with alignment. Because it’s difficult to get two surfaces to be flush, it’s best to make the transition strip at a different elevation than the two ceiling materials. Transition strips also highlight the change in ceiling finishes.

As with wall reveals, a ceiling reveal visually separates two different materials and provides an interesting shadow line. A reveal also disguises any minor misalignment between the two edges.

A feature strip is used when the ceiling finishes or substrates are the same thickness. It provides an easy, inexpensive way to conceal the joint thickness and any misalignment of the edges of the finish. Like a transition strip, a feature strip also highlights the change in ceiling materials or finishes.

--- Planar transition details: (a) butt joint with ceiling trim (b) transition strip (c) in-plane ceiling reveal (d) feature strip optional feature strip ceiling angle wallboard L-angle wallboard framing as required metal framing suspended from structure above aluminum trim wallboard framing as required.

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In-Plane Transitions

In-plane transitions occur when two adjacent ceilings are flush or nearly flush with each other. There are four basic ways of designing this type of transition.

ABUTTING

Abutting ceilings are the same as abutting walls or floors. Two materials or finishes touch each other along a single line and are flush or nearly flush. Butt joints minimize the change in ceiling materials and keep the ceiling elevation constant. This is a simple joint to make, but as with other butt joints, it’s sometimes difficult to get both materials to align perfectly and finishing may be difficult. Butt joints are also only appropriate for certain materials. Gypsum wallboard and acoustical ceiling tile, E.g., may be aligned but require some type of trim between them to support the edges of both materials. As shown, a white, aluminum extrusion can be used to serve this purpose without being obvious, but it’s still not a true butt joint.

TRANSITION STRIP

A transition strip is a third material placed between two ceiling surfaces to emphasize the transition, to add visual interest to the ceiling, or to accommodate slightly different substrate thicknesses. The transition strip can be flush with one of the surfaces, both surfaces, or neither surface, depending on the design concept or the functional requirements of the detail. Transition strips are relatively easy to apply on gypsum wallboard ceilings but may be difficult to apply to acoustical ceilings. --- shows one method of using a wood strip with a wallboard ceiling, while using it to support the ceiling angle for an acoustical ceiling.

--- Offset ceiling transitions: (a) sharp edge (b) angle or curve (c) emphasized edges (d) overlap (e) bulkhead A sharp edge is the most common type of ceiling transition and can be formed with almost any material, including acoustical ceiling systems. However, the vertical portion is most commonly gypsum wallboard.

An angle or curve gives a more gentle transition between two ceiling planes and can be an effective design, especially when combined with similar shapes used elsewhere in the space.

Emphasized edges are used to draw attention to the ceiling transition and to add interest the change in plane. The edges can be treated with any material and can be traditional wood trim or contemporary in feeling.

An overlap gives a lighter feeling to a ceiling height transition than other types, making it appear that one ceiling floats below the other. The portion inside the overlap can conceal HVAC registers or indirect lighting.

A bulkhead creates a strong volumetric feeling to the space below the upper ceiling. Combined with a raised floor this design can strongly differentiate one space from another.

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REVEAL

A reveal is a noticeable gap between the two ceiling materials. As with wall reveals, a ceiling reveal conceals any slight misalignment of the surfaces, adds visual interest, creates a clear separation between two materials, and may make finishing easier. A reveal may be created by simply separating the two materials by the desired amount if they have a finished edge, or by using a preformed aluminum trim.

FEATURE STRIP

A feature strip is a third material placed over the joint of the two ceiling surfaces, much like a batten strip used for wall transitions. Featured strips provide a functional way to easily finish a joint, while emphasizing the transition between the two ceiling finishes.

One way to detail this is shown.

Offset Transitions

Offset transitions occur where the adjacent ceiling planes are at obviously different elevations.

Offset transitions are required to create many of the ceiling concepts.

There are five basic types of ceiling-to-ceiling transitions.

SHARP EDGE

A sharp edge is simply a 90-degree change from the lower horizontal ceiling plane to the upper plane. The vertical portion of this type of offset can be constructed of any material but gypsum wallboard is most commonly used whether the horizontal planes are wallboard, suspended acoustical tile, or other materials. Gypsum wallboard and its support framing allow a wide variety of trims and other construction elements to be attached to support any type of ceiling system. If acoustical tile is used for the two horizontal plans details such as those shown can be used.

ANGLED OR CURVED EDGE

The transition between ceilings can also be made with a sloped plane set at any angle that is appropriate for the design concept. It may also be made with a curved pro file. The transition may be made with the same material as the horizontal portions or a different material. E.g., the curve or angle may be gypsum wallboard, while the two level portions can be wallboard, acoustical tile, or other ceiling finishes.

EDGES EMPHASIZED

Emphasized edges are used when the ceiling transition needs to be highlighted. The emphasis may be created with applied trim or, if the ceiling is gypsum wallboard, by building up the desired pro file with wallboard.

Special aluminum trim may also be used to emphasize the edges. Three examples of proprietary trim are shown that combine emphasized edges with an angled transition.

OVERLAP

An overlap transition is one in which the lower ceiling plane is extended beyond the vertical connection so it appears the lower ceiling is floating below the upper ceiling. The elevation difference is determined by the design concept, the desired ceiling height, and by the limitations of structure and mechanical services above the upper ceiling.

The space between the two ceilings can be used for indirect lighting, to conceal air supply registers, or can be left open.

BULKHEAD

A bulkhead is a vertical construction element extending from the upper ceiling to well below the lower ceiling. This detail emphasizes the transition as well as creating a strong sense of spatial volume below the upper ceiling. This design approach is especially effective when coordinated with a differentiated floor finish or a raised ground plane.

Bulkheads are easily constructed with gypsum wallboard framing suspended from the structure above similar to the detail shown except that the lower edge of the bulkhead is extended farther below the elevation of the lower ceiling.

----Emphasized edges: (a) wood trim (c) aluminum trim edges 2" (51) 1" (25) aluminum trim metal framing wood trim as designed attached to metal framing gypsum wallboard acoustical ceiling nested long leg runners gypsum wallboard ceiling system 2" (51) (b) built-up edge section as designed standard aluminum trim sections

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