CONSTRAINTS to Interior Design

Home | Fire Safety | Skyscrapers

Home Emergencies | Glossary


In construction detailing, constraints include any limitation over which the designer has little or no control. In conjunction with design intent and function, determining constraints is part of any problem-solving process because it helps define the problem. This section discusses some of the common constraints encountered in interior construction detailing and gives some reference information for common detailing conditions. Not included here are client preferences, which may include a directive to the designer to use a particular material or not use a material or construction technique.

Although they are usually fixed, some constraints may be questioned, such as budget, regulatory requirements, industry standards, and local construction practices. For budget, the designer may investigate whether a budget can be reallocated to allow more money for one detail if less money is given to another detail. If a regulatory requirement prevents the use of a particular material, the designer may think it’s important enough to explore getting a variance or doing the research necessary to convince the local authority having jurisdiction that the proposed material is equivalent. This can often be done with an IBC evaluation report that manufacturers obtain for new materials not yet in the building code.

Good designers can often turn a constraint into an asset. E.g., a limited budget forces the designer to focus on the essential aspects of the problem and may suggest new, innovative ways to solve a problem, which can lead to a unique design solution.

Although constraints may be determined at any time during the detailing process, the detailer should first determine those that are the most restrictive and work toward those that are the least restrictive, as shown in ill. 1.

As the constraints are determined, record them as sketches that can serve as quick re minders during the detailing process. ill. 2 shows two quick sketches that consolidate existing conditions and code requirements for an entry into a bar from a hotel lobby. Concept alternatives for this design are shown in ill. 7.

ill. 1 Sequence of determining constraints Determine and record existing substrates and conditions Determine regulatory requirements Sketch and note constraints Understand budget, schedule, and climate Determine local construction practices and trade conditions Recognize industry standards and material qualities

ill. 2 Sketch of constraints

Tbl. 1 Substrates for Interior Details

Substrate Material

Concrete Masonry Solid wood Panel products Aluminum Steel, structural Steel, light gage Gypsum wallboard



Hard and dense with high strength

Hard and brittle; typically not used for interior work except for fire-rated or security partitions

Relatively strong and most softwoods used for framing have good holding power for nails and screws

Particleboard, oriented strand board, medium-density fiberboard Lightweight; can be used structurally or as a finish material; many extruded shapes or can be custom extruded; accepts a wide variety of finishes

Very strong with high strength-to-weight ratio

Very flexible for wall and ceiling framing, as well as soffits and other constructions; noncombustible

Good wall finish material for painting and other finishes; excellent sound attenuation and fire resistance; easy to attach fasteners


Typical Sizes/Thicknesses:

Floors typically 4 in. to 6 in. (102 mm to 152 mm) thick;

walls 8 in. to 12 in. (203 mm to 305 mm) thick 8 in. x 8 in. x 16 in. (200 × 200 × 400 mm) blocks Standard 2 × 4 (1-1/2 in. x 3-1/2 in. [38 mm x 89 mm]; others 2 in. x 6 in., 2 in. x 8 in., 2in.x10in.

Thicknesses from 1/4 in. to 1-1/4 (6.4 mm to 32 mm) with 3/4 in. (19 mm) most common Extruded shapes vary by manufacturer; available in tubes, angles, bars, and channel shapes as well as sheets Sizes based on type; available in bars, tubes, pipes, angles; Z bars, H-shapes, lightweight I beams 1-5/8 in., 2-1/2 in., 3-5/8 in., 4 in., and 6 in. deep studs; runners, J-shapes, angles, and various other specialty shapes for wall framing 1/4 in., 3/8 in., 1/2 in., 5/8 in., 3/4 in. (6.4 mm, 10 mm, 13 mm, 16 mm, 19 mm) thick boards, 4 in. wide sheets 8 ft, 10 ft, 12 ft, and 14 ft long


Fasteners Used:

Power actuated fasteners, expansion bolts, adhesive for lightweight products Power-actuated fasteners, molly bolts, and adhesive for panel products Nails, power staples, screws, through-bolts Screws, bolts, mastic, nails, Screws, bolts, mastic for lightweight material;

heavier aluminum can be welded and bolted Welding, power-actuated fasteners, through bolting, drill and tap for screws Self-tapping screws, through bolts, molly bolts Plastic anchors, molly bolts, hollow wall anchors, toggle bolts, various proprietary fasteners;

screws directly into studs


Other Concerns:

Floors and walls contain reinforcing steel; however, most fasteners for interior detail anchoring don’t con flict.

Generally requires wood or metal furring to attach wallboard or other finishes May shrink; nails may pop out Strong material but with low pullout resistance for some fasteners Galvanic action is a concern with fasteners and other metals touching the aluminum Galvanic action is a concern with fasteners and other metals touching the steel.

Galvanic action is a concern with fasteners and other metals touching the steel Wallboard by itself cannot hold large loads (see Tbl. 4); may need wood blocking in metal stud walls for support


Interior design details are always part of an existing structure. The interior designer is working either within an existing building or on a building being planned or under construction for which architectural plans are available. Basic components, such as floor structure, ceiling construction, columns, exterior walls, and windows, are all known elements as are the base building mechanical, plumbing, and electrical systems. Unless the interior designer is working with an architect and planning major modifications to an existing building, these elements are generally the basic structural constraints with which the designer must work.

In developing an interior construction detail, the designer may be limited in what is possible because of existing conditions. E.g., a relatively thin concrete floor may preclude the use of a floor-mounted door closer, and detailing may require a larger head frame for a concealed overhead closer. In some cases, even existing building services may preclude some design details. An existing main supply air duct, for instance, may prevent making a raised ceiling detail higher than the existing ceiling line.

There are basically four aspects of existing construction that the interior designer must contend with during detailing: substrate material, condition of the substrate, size and position of substrate elements, and available space allowed by the substrates.

Substrate Material

The substrate material refers to the type of material on which or to which the interior detail is attached or touches. Different substrate materials may require different responses. E.g., attachment of ornamental metal to an existing steel structural member must take into account possible galvanic action when different metals are in contact with each other. The metals may need to be separated with a plastic or neoprene spacer to prevent direct contact. Some of the common substrate materials and their basic characteristics are shown in Tbl. 1.

Some substrate materials may also be limited in their inherent strength. E.g., it may be more difficult to attach wall-mounted items to a partition framed with metal studs than one with wood studs. See Tbl. 4 for load capacities of some common fasteners in studs.

Substrate Condition

Substrate condition is the strength and appearance of the base material to which the interior de tail is attached. In most cases, the strength is the most important characteristic because if affects the ability of the new detail to be adequately supported without additional construction. E.g., existing, spalling concrete in an old building may not provide the required strength for anchoring a bolt as well as new concrete. If the strength of any component or connection is a concern, a structural engineer or architect should be consulted for recommendations.

In some detailing situations, the substrate material may be fully or partially visible, in which case its appearance may also be of concern. It may have to be cleaned, painted, refinished, or otherwise modified to make it suitable for the new detail.

Substrate Size and Position

The size and/or position of the substrate may affect how a detail is designed. The thickness of wood subflooring, E.g., may dictate how new flooring is anchored or the spacing of floor joists may influence how partitions are anchored to the structure above.

Substrate Space

Substrate space is space available for a portion of the new detail or for its attachment, including clearances required for tools and workspace. This is typically stud depth and spacing, floor or ceiling joint depth and spacing, or clearance around structural beams and columns. It can also include space in architectural woodwork, above ceilings, in mechanical chases, and around the exterior cladding of buildings. The designer must understand tools and construction processes to provide sufficient space to allow a worker to build the detail.

Tbl. 2 IBC Requirements for Interior Partition Materials

Construction Element Accessories Wall framing Wall framing Wall framing Wall framing Wall framing Gypsum wallboard Gypsum wallboard Gypsum wallboard Gypsum wallboard Gypsum wallboard Gypsum wallboard Gypsum wallboard Gypsum wallboard Gypsum wallboard Gypsum plaster Gypsum plaster Gypsum plaster Gypsum plaster Gypsum plaster Gypsum plaster Gypsum plaster


Agency | Standard Number

  • ASTM C1047 AISI S211 AISI S212 ASTM C754 ASTM C954 ASTM C955
  • ASTM C840
  • ASTM C960
  • ASTM C1002
  • ASTM C1395
  • ASTM C1396
  • ASTM C1629
  • ASTM C1658
  • GA 216
  • GA 600
  • ASTM C28/C28M
  • ASTM C587
  • ASTM C588
  • ASTM C842
  • ASTM C843
  • ASTM C844
  • ASTM C847-06

Standard Name:

Specification for Accessories for Gypsum Wallboard and Gypsum Veneer Base North American Standard for Cold-formed Steel Framing-Wall Stud Design North American Standard for Cold-formed Steel Framing-Header Design Specification for Installation of Steel Framing Members to Receive Screw-attached Gypsum Panel Products Specification for Steel Drill Screws for the Application of Gypsum Panel Products or Metal Plaster Bases to Steel Studs from 0.033 inch (0.84 mm) to 0.112 inch (2.84 mm) in Thickness Standard Specification for Load-bearing Transverse and Axial Steel Studs, Runners Tracks, and Bracing or Bridging, for Screw Application of Gypsum Panel Products and Metal Plaster Bases Specification for Application and Finishing of Gypsum Board Specification for Predecorated Gypsum Board

Specification for Steel; Self-piercing; Tapping Screws for the Application of Gypsum Panel Products or Metal Plaster Bases to Wood Studs or Steel Studs

Specification for Gypsum Ceiling Board

Specification for Gypsum Board

Standard Classification for Abuse-resistant Nondecorated Interior Gypsum Panel Products and Fiber-reinforced Cement Panels

Standard Specification for Glass Mat Gypsum Panels Application and Finishing of Gypsum Panel Products Fire-resistance Design Manual.

Specification for Gypsum Plasters Specification for Gypsum Veneer Plaster Specification for Gypsum Base for Veneer Plasters Specification for Application of Interior Gypsum Plaster Specification for Application of Gypsum Veneer Plaster Specification for Application of Gypsum Base to Receive Gypsum Veneer Plaster

Specification for Metal Lath


Tbl. 3 IBC Requirements for Quality of Common Interior Materials Other Than Partitions Construction Element Agency Standard Number Standard Name Ceilings Acoustical ceilings ASTM C635 Specification for the Manufacture, Performance and Testing of Metal Suspension Systems for Acoustical Tile and Lay-in Panel Ceilings Acoustical ceilings ASTM C636 Practice for Installation of Metal Ceiling Suspension Systems for Acoustical Tile and Lay-in Panels Doors WDMA 101/I.S.2/A440 Specifications for Windows, Doors, and Unit Skylights Fire doors NFPA 80 Fire Doors and Other Opening Protectives Hardware UL 305 Panic Hardware UL 325 Door, Drapery, Gate, Louver and Window Operations and Systems Power-operated BHMA A156.10 Power Operated Pedestrian Doors Power-operated BHMA A156.19 Standard for Power Assist and Low Energy Operated Doors Glazing/windows Glass ASTM E1300 Practice for Determining Load Resistance of Glass in Buildings Safety glazing CPSC 16 CFR 1201 Safety Standard for Architectural Glazing Material Windows ASTM F2090 Specification for Window Fall Prevention Devices with Emergency Escape (Egress) Release Mechanisms Tile Ceramic tile ANSI A108 series Installation of Ceramic Tile (various methods in this series) Ceramic tile ANSI A118 series Standards for Mortar and Grout (various types in this series) Ceramic tile ANSI A136.1 American National Standard for Organic Adhesives for Installation of Ceramic Tile Ceramic tile ANSI A137.1 American National Standard Specifications for Ceramic Tile Wood Glulam construction AITC 04 Typical Construction Details Hardboard ANSI A135.4 Basic Hardboard Panels DOC PS-2 Performance Standard for Wood-based Structural Panels Particleboard ANSI A208.1 Particleboard Plywood DOC PS-1 Structural Plywood HPVA HP-1 Standard for Hardwood and Decorative Plywood Wood framing DOC PS-20 American Softwood Lumber Standard Agencies:

AITC American Institute of Timber Construction ANSI American National Standards Institute ASTM International BHMA Builders Hardware Manufacturers' Association CPSC Consumer Product Safety Commission DOC U.S. Department of Commerce HPVA Hardwood Plywood Veneer Association NFPA National Fire Protection Association UL Underwriters Laboratories WDMA Window and Door Manufacturers Association Note: masonry and metal products not included in this table


Tbl. 4 Summary of Tests for Flammability of Interior Design Components Common Name Application Test Number(s) Floor finishes Flooring radiant panel test Carpet, resilient floors, and other floor coverings in corridors NFPA 253 (ASTM E648) Methenamine pill test Carpets and rugs 16 CFR 1630 (ASTM D2859) Floor/ceiling construction Wall and floor/ceiling assembly test Fire ratings of walls, structure, and floor construction assemblies ASTM E119 Wall finishes Steiner tunnel test Flame-spread rating of finishes ASTM E84 Room corner test Evaluates extent to which wall and ceiling finish (other than textiles) contributes to fire growth NFPA 286 Room corner test for textiles Contribution of textile wall finish to fire growth in full-scale mockup NFPA 265 Wall construction Wall and floor/ceiling assembly test Fire ratings of walls, structure, and floor construction assemblies ASTM E119 Ceiling finish Steiner tunnel test Flame-spread rating of finishes ASTM E84 Alternate to E84 Evaluates extent to which wall and ceiling finish (other than textiles) contributes to fire growth NFPA 286 Door/glass openings Fire tests of door assemblies Endurance test of doors to flame and heat transfer NFPA 252 (UL 10C) Fire tests of window assemblies Endurance of glazing for 45 minutes to flame and heat transfer, including glass block NFPA 257 Fire tests of fire-resistance-rated glazing Endurance of glazing when tested as a transparent wall ASTM E119 Trim and decorative materials Decorative materials Draperies, curtains, and other window treatment as well as banners, awnings, and fabric structures NFPA 701 Foam plastic used as trim Maximum flame spread index of 75 with limitations on density, thickness, and total area within a room ASTM E84 Trim such as baseboards, chair rails, picture molds, door and window frames Flame-spread rating with minimum Class C, excluding handrails and guardrails ASTM E84 Window coverings Vertical ignition test Draperies, curtains, and other window treatment as well as banners, awnings, and fabric structures NFPA 701 Requirements based on 2009 International Building Code



Regulatory requirements usually affect detailing in terms of a material's quality, strength, and flammability. Accessibility laws may also affect how materials are selected for some details and how they are sized and con figure d.

Tbl. 2 and 2-3 summarize some of the regulatory requirements for interior materials as found in the International Building Code (IBC). However, the standards listed in Tbl. 2 and 2-3 are only those to which the IBC refers. There are hundreds of additional ASTM, ANSI, and industry standards that apply to interior construction elements. A partial list of these standards for various products is shown in Appendix A. These standards can be used to evaluate materials and to include when specifying them in the final project documents and are especially useful when evaluating new or innovative products.

Flammability and fire resistance are especially important when selecting materials for details or developing details for construction assemblies such as partitions and openings.

Tbl. 4 summarizes some of the flammability requirements for interior components and finishes as regulated by the IBC. The following sections describe these in more detail.

Fire Tests for Finish Materials

Flammability tests for finish materials determine the following:

++ Whether a material is flammable, and if so, if it simply burns with applied heat or if it supports combustion (adds fuel to the fire)

++ The degree of flammability (how fast fire spreads across the material)

++ How much smoke and toxic gas the material produces when ignited evaluate materials and to include when specifying them in the final project documents and are especially useful when evaluating new or innovative products.

Flammability and fire resistance are especially important when selecting materials for details or developing details for construction assemblies such as partitions and openings.

Tbl. 4 summarizes some of the flammability requirements for interior components and finishes as regulated by the IBC. The following sections describe these in more detail.

Fire Tests for Finish Materials Flammability tests for finish materials determine the following:

++ Whether a material is flammable, and if so, if it simply burns with applied heat or if it supports combustion (adds fuel to the fire)

++ The degree of flammability (how fast fire spreads across the material)

++ How much smoke and toxic gas the material produces when ignited Several tests are typically used for building and interior construction as briefly described in the following list.


ASTM E84, Standard Test Method for Surface Burning Characteristics of Building Materials, is one of the most common fire-testing standards. It’s also known as the Steiner tunnel test and rates the surface burning characteristics of interior finishes and other building materials by testing, in a narrow test chamber, a sample piece with a controlled flame at one end. The primary result is a material's flame-spread rating compared to glass-reinforced cement board (with a rating of 0) and red oak flooring (with an arbitrary rating of 100). ASTM E84 can also be used to generate a smoke developed index, which is a number representing the amount of smoke generated as a material burns in the test chamber.

With this test, materials are classified into one of three groups. A, B, or C, based on their tested flame-spread characteristics. These groups and their flame-spread indexes are given.

Class A is the most fire resistant. Product literature generally indicates the flame spread of the material, either by class (indicated with a letter, A, B, or C) or by numerical value of I, II, or III. The IBC then specifies the minimum flame-spread requirements for various occupancies in specific areas of the building.

Traditionally, the E84 test was used exclusively for interior finishes, but the IBC also allows the use of finish materials other than textiles if they meet requirements set forth in the IBC when tested in accordance with NFPA 286 and when a Class A finish would otherwise be required.

NFPA 253

NFPA 253, Standard Method of Test for Critical Radiant Flux for Floor Covering Systems Using a Radiant Heat Energy Source. Also called the Flooring Radiant Panel Test, this procedure tests a sample of floor covering mounted on a typical substrate in the normal horizontal position and measures the flame spread in a corridor or exit way that is under the influence of a fully developed fire in an adjacent space. The resulting test numbers are measured in watts per square centimeter; the higher the number, the more resistant the material is to flame propagation.

This is the same test as ASTM E648.

Two material classes are defined by NFPA 253: Class I and Class II. Class I materials have a critical radiant flux of 0.45 W/cm2 or greater, and Class II materials have a critical radiant flux of 0.22W/cm2 or greater. Class I finishes are typically required in corridors and exitways of hospitals, nursing homes, and detention facilities. Class II flooring is typically required in corridors and exitways of other occupancies, except one- and two-family dwellings. The IBC establishes criteria that limit the critical radiant flux of flooring material for textile coverings or coverings composed of fibers. The IBC specifically excludes traditional flooring types such as wood, vinyl, linoleum, and terrazzo. It also allows Class II materials in sprinklered buildings where Class I materials might otherwise be required.

NFPA 265

NFPA 265 is the Method of Fire Tests for Evaluating Room Fire Growth Contribution of Textile Wall Coverings on Full Height Panels and Walls. Also called the Room Corner Test for Textile Wall Coverings, this test determines the contribution of interior wall and ceiling textile coverings to room fire growth. It attempts to simulate real-world conditions by testing the material in the corner of a full-sized test room. It was developed as an alternate to the ASTM E84 Steiner tunnel test.

NFPA 286

NFPA 286 is the Standard Methods of Fire Test for Evaluating Contribution of Wall and Ceiling Interior Finish to Room Fire Growth. Also called the Room Corner Test, this standard was developed to address concerns with interior finishes that don’t remain in place during testing according to the E84 tunnel test. It’s sometimes required in addition to or instead of an ASTM E84 rating for interior finishes. The 286 test evaluates materials other than textiles.

It’s similar to NFPA 265 in that materials are mounted on the walls or ceilings inside a room, but more of the test room wall surfaces are covered, and ceiling materials can be tested.

This test evaluates the extent to which finishes contribute to fire growth in a room, assessing factors such as heat and smoke released, combustion products released, and the potential for fire spread beyond the room.

NFPA 701

NFPA 701 is the Standard Methods of Fire Tests for Flame Propagation of Textiles and Films. This test, also called the Vertical Ignition Test, establishes two procedures for testing the flammability of draperies, curtains, or other window treatments. Test 1 provides a procedure for assessing the response of fabrics lighter than 21 oz/yd^2 individually and in multilayer composites used as curtains, draperies, and other window treatments. Test 2 is for fabrics weighing more than 21 oz/yd^2 , such as fabric blackout linings, awnings, and similar architectural fabric structures and banners. NFPA 701 is appropriate for testing materials that are exposed to air on both sides. A sample either passes or fails the test.

16 CFR 1630

Another test for carpet flammability is the Code of Federal Regulations, 16 CFR Part 1630 (also ASTM D2859, Standard Test Method for Ignition Characteristics of Finished Textile Floor Covering Materials), also known as the Methenamine Pill Test, which is required for all carpet sold and manufactured in the United States. A test sample of the carpet is placed in a draft protected cube and held in place with a metal plate with an 8-in. (203-mm) diameter hole.

A timed methenamine pill is placed in the center and lighted. If the sample burns to within 1 in. (25 mm) of the metal plate, it fails the test. This is also sometimes called by an older designation, DOC FF-1.

Fire Tests for Construction Assemblies The following summaries include fire testing for building assemblies such as partitions, door openings, and ceiling/floor assemblies.


One of the most commonly used tests for fire resistance of construction assemblies is ASTM E119, Standard Test Methods for Fire Tests of Building Construction and Materials. This test involves building a sample of the wall or floor/ceiling assembly in the laboratory and burning a controlled fire on one side. Monitoring devices measure temperature and other aspects of the test as it proceeds.

There are two parts to the E119 test. The first measures heat transfer through the assembly.

The goal of this test is to determine the temperature at which the surface or adjacent materials on the side of the assembly not exposed to the heat source will combust. The second is the hose stream test, which uses a high-pressure fire hose stream to simulate an impact from falling debris to evaluate how well the assembly stands up to it and the cooling and eroding effects of water. Overall, the test evaluates an assembly's ability to prevent the passage of fire, heat, and hot gases for a given amount of time.

For construction assembly testing according to ASTM E119, a time-based rating is given to the assembly. In general terms, this rating is the amount of time an assembly can resist a standard test fire without failing. The ratings are 1 hour, 2 hours, 3 hours, and 4 hours. Doors and other opening assemblies can also be given 20-minute, 30-minute, and 45-minute ratings.

NFPA 252

NFPA 252, Standard Methods for Fire Tests of Door Assemblies, evaluates the ability of a door assembly to resist the passage of flame, heat, and gases. It establishes a time-endurance rating for the door assembly, and the hose stream part of the test determines if the door will stay within its frame when subjected to a standard blast from a fire hose after the door has been subjected to the fire-endurance part of the test. Similar tests include UL10B, UL10C, and UBC 7-2.

NFPA 257

NFPA 257, Standard for Fire Test for Window and Glass Block Assemblies, prescribes specific fire and hose stream test procedures to establish a degree of fire protection, in units of time, for window openings in fire-resistive walls. It determines the degree of protection from the spread of fire, including flame, heat, and hot gasses.


The budget for an interiors project is usually fixed and, in the designer's mind, never enough to do the job adequately. However, like other constraints, the budget can be a generator of design ideas and solutions whether is it low or high. A low budget may force the designer to explore new ways of using inexpensive materials and construction processes, while a generous budget may encourage exploration into materials and solutions that the designer might otherwise not investigate.

Even though a budget is fixed there are three ways to use it: by reallocation, phasing, and life-cycle costing. Reallocation is simply setting priorities concerning what is most important in the overall design and using more of the budget in those areas and less where it may not be as important. E.g., in an office design, it may be more important to spend more of the budget in the public reception and conference areas than in private offices. The designer may even suggest forgoing private offices for systems furniture to reduce construction costs and where the purchase may have beneficial tax advantages for the client.

Phasing is the postponement of building a portion of the interior until more money is available. The designer may feel it’s critical for the success of the project to put the available budget into certain areas, while waiting to complete other portions of the project.

E.g., basic partition and ceiling finishes can be used until money is available for more decorative treatments and improved functionality. Of course, the reality of this approach is that more money is seldom available or the client will elect never to make the additional improvements.

Life-cycle costing is more than examining just the first costs of construction. Instead, it determines what the cost is over the life of the product or material, including the maintenance costs of a material, its expected service life, its replacement costs, disposal costs, and the value of money over time. Although not technically a way to use an existing budget, the technique may be used to convince a client it’s in their economic interest to budget more money initially. E.g., one flooring material may have a higher first cost than another but will last longer and require lower maintenance and disposal costs over its service life and, in the long run, be less expensive for the client.

Whether or not life-cycle costing is important depends on the type of client. If the client will the owner of the facility and be responsible for its maintenance, then long-terms costs are important. If the client is a tenant and expects only short-term use and won’t be responsible for maintenance and replacement, then only first costs are likely to be important. It’s beyond the scope of this guide to discuss the methods in detail but one good resource is Life Cycle.

In the detailing process the designer can most affect the cost of construction in material selection and the complexity of details. In many cases, a less expensive finish material can achieve the same goals as a more expensive material without compromising the look and overall effect of the design. As discussed in Section 4, the designer can also minimize costs by developing a detail with the least number of components and connections, and by minimizing the number of construction trades involved and the time it takes to build the detail.


In the construction industry, time is always a constraint. It’s closely related to budget in that the longer it takes to design and build generally the more money it takes, unless the contractor is working on a strictly fixed price basis. The interior designer is usually under constant pressure to produce the design and construction documentation as fast as possible. In turn, accurate, innovative, and efficient details must be completed as quickly as possible. If time is limited, the designer may decide to use simple, standard details that can be developed quickly without excessive research, development, review, and documentation. In turn, standard details generally require less time to build than custom details.

When selecting materials, availability is an important criterion as it relates to how easily a product can be obtained and if it can be delivered to the job site in time to maintain the overall project schedule. Some specialty products can require six months or more to get. Other products are in stock for immediate delivery but may only be available in a limited choice of colors or finishes. Some products are specifically available in "quick ship" programs to meet tight schedules.


Although climate does not influence interior design nearly as much as architectural design, it can nonetheless affect some material and detailing decisions. The orientation of windows and sun angle can influence the type of window coverings and selection of materials that may fade in the sunlight. Hard, durable, easy-to-clean flooring materials near entrances may be warranted in climates where snow, rain, and mud are tracked into the building. In very dry climates, wood should be detailed differently than in humid climates to conceal the inevitable shrinkage. If the building in which the interior project is located was built to use passive solar design, the choice of interior materials and construction should not compromise this intent.


The local labor market for an interior design project can affect the selection of materials and construction techniques in four ways. These include the availability of skilled labor, the common trade divisions of labor, the use of union or nonunion workers, and the preferred local materials and construction methods.

First, every interior design project, residential or commercial, requires some type of skilled labor, whether it’s as simple as painting or as complex as installing a custom stair involving steel, glass, stone, and other materials. Most large urban markets have an abundance of skilled labor in all trades, while smaller cities and rural areas may not. If cost and time are important constraints, the detailer may want to select materials and develop details that the local labor market can readily construct. The alternate is to have skilled labor brought in from other areas, usually at a significant cost. Even for projects in large cities, some specialty product manufacturers often insist on using their own installers or approved installers, who may be far removed from the project locale.

Second, the construction industry has developed commonly accepted divisions of labor;

that is, one type of worker will only do particular work. A plumber, E.g., does not install gypsum wallboard. For every trade worker involved in a detail, the cost increases. The best approach to detailing is to design the detail to minimize the number of separate trades that must work on it.

A related factor is the sequence of labor. In most cases, tradespeople don’t want to be working in the same area of the project as other trades and generally only want to come on a job site once. A detail that requires a trade to do one portion of a job, leave the job site, and come back later to do additional work will cost more, and such a detail runs the risk of slowing the job if the trade cannot come back at the appropriate time to finish its work.

E.g., a complex partition detail should not require drywall finishers to finish part of their work before the carpenters can place additional framing, which then requires the finishers to return to complete their work. This type of detail would only be efficient if the drywall finishers could be working on another part of the job while the carpenters prepared the framing for them. Tbl. 6 lists some of the common trade names and the type of work they do as well as the unions that represent the workers when union labor is involved.

The third way labor can affect detailing is whether or not union or nonunion workers will be involved. Again, if cost is a consideration, union work on a detail may be slightly more expensive than having it built by nonunion workers. The robustness of the local labor market may also affect the cost of building. When business is good and competition low, price estimates are usually higher than in sluggish markets. Both of these factors may suggest how complex a detail should be given the client's budget. Refer to the various union web sites given in Tbl. 6 for more information.

Finally, any given labor market has preferred materials and methods of building. E.g., in the northeast part of the United States, it’s common for gypsum veneer plaster to be used whereas in the Midwest, gypsum wallboard is only finished at the joints and fastener locations. When working in a new or unfamiliar market, the interior designer should talk with local designers and contractors to determine local trade practices.


Tbl. 6 Trade Divisions of Labor Trade Name Work Performed Trade Union Carpenter, residential carpenter Residential rough and finish carpentry, residential flooring UBC Carpenter, interior systems carpenter Metal studs and framing, suspended ceiling systems, wood trim, specialty interior products UBC Carpenter, lather/drywaller Lath for plaster UBC Carpenter, cabinet maker/millworker Architectural woodwork, store fixtures, furniture UBC Carpenter, floor layer Carpet, hardwood flooring, resilient flooring UBC Drywall finisher Drywall taping and finishing IUPAT Plasterer Plastering, concrete construction, cement finishing OPCMIA Flooring installer Carpet, resilient flooring, prefinished hardwood, Laminate flooring, seamless flooring,

flooring trim and accessories, underlayment IUPAT Mason Stone and marble masonry, tile setting, terrazzo and mosaic BAC Painter Painting, wallcovering, stretched fabric systems, plastic wallcoverings, wall accessories and trim IUPAT Glazier Glass, mirrors, decorative glass, glass handrails, shower enclosures, aluminum storefront frames, suspended glass systems, column covers, glass doors IUPAT Ornamental iron worker (finisher) Ornamental metal, metal stairs, gratings and ladders, railings, elevator fronts, metal screens IABSORIW Sheet metal worker Architectural sheet metal work, HVAC, heating and air conditioning ducts SMWIA Sign and display worker Signage, trade show decorators, metal polishing IUPAT Electrician (inside wireman) Electrical, computer cabling, telecommunications IBEW Plumber Plumbing UA Sprinkler fitter Sprinkler systems UA Elevator contractor Elevator installation and remodeling IUEC Steel worker (steel fixer) Reinforcing bar for concrete IABSORIW BAC International Union of Bricklayers and Allied Craft workers IABSORIW International Association of Bridge, Structural, Ornamental and Reinforcing Iron Workers IBEW International Brotherhood of Electrical Workers IUEC International Union of Elevator Contractors IUPAT International Union of Painters and Allied Trades OPCMIA Operative Plasterers' and Cement Masons' International Association SMWIA Sheet Metal Workers International Association UA United Association of Journeymen and Apprentices of the Plumbing and Pipe Fitting Industry of the United States and Canada UBC United Brotherhood of Carpenters and Joiners of America


ill. 3 Common metal framing components 5/16" (8) 1 1/4" (32) 1 5/8" (41) 2 1/2" (64) 3 5/8" (92) 4" (102) 6" (152) 1" (25) 1 1/4" (32) stud width 2 1/2" (64) 4" (102) 6" (152) 2" (51) 1" (25) 3/4" (19) 1 1/2" (38) 1/2" (13) 1 1/4" (32) 7/8" (22) 2 9/16" (65) 1 3/8" (35) 7/8" (22) 1 1/2" (38) 2 1/2" (64) 1/2" (13) 2 1/2" (64) 2 1/2" (64) (d) angle runner (f) cold-rolled channel (h) resilient channel (i) Z-furring channel (e) corner angle (c) J-runner (g) furring channel 1" (25) 1 1/2" (38) 2" (51) 3" (76) 1 1/4" (32) 7/8" (22) (a) studs (b) runners ill. 4 Glazing framing dimensions bite edge face butt joint see Table 2.9 glass sizes see Table 2.7 see Table 2.8 for clearances

- Tbl. 7 Approximate Maximum Glass Sizes Based on Type and Thickness Glass Type Thickness, in. (mm) Maximum Size, in. (mm) Float glass 1/8 (3) 102 × 130 (2590 × 3300) 1/4 (6) 130 × 200 (3300 × 5080) Tempered glass 1/8 (3) 42 × 84 (1067 × 2134) 3/16 (5) 78 × 102 (2000 × 2600) 1/4 (6) 78 × 165 (2000 × 4200) 3/8 (10) 78 × 165 (2000 × 4200) 1/2 (12) 78 × 165 (2000 × 4200) 3/4 (19) 71 × 158 (1800 × 4000) Laminated glass 13/64 (5.2) 84 × 130 (2134 × 3300) 9/32 (7.1) 84 × 144 (2134 × 3658) 1/2 (13) 84 × 180 (2134 × 4570) Bent glass, tempered 1/4 (6) 130 × 72 (curve) (3300 × 1830) 1/2 (12) 130 × 84 (curve) (3300 × 2134) Fire-resistant rated (requires manufacturer's special framing) 45 min., 3/4 (19) 95 × 95 (2413 × 2413) 60 min., 15/16 (23) 95 × 95 (2413 × 2413) 90 min., 1-7/16 (37) 90 × 90 (2286 × 2286) Source: manufacturers' catalogs. Sizes are only approximate; consult individual manufacturers for specific limits on size based on glass type and thickness.

Tbl. 8 Recommended Face and Edge Clearance for Interior Glass Minimum Clearance, in. (mm) Glass Thickness, in. (mm) Face Edge Bite 1/8 (3) 1/8 (3.2) 1/4 (6.4) 3/8 (9.5) 3/16 (5) 1/8 (3.2) 1/4 (6.4) 3/8 (9.5) 1/4 (6) 1/8 (3.2) 1/4 (6.4) 3/8 (9.5) 5/16 (8) 3/16 (4.8) 5/16 (7.9) 7/16 (11.1) 3/8 (10) 3/16 (4.8) 3/16 (4.8) 7/16 (11.1) 1/2 (12) 1/4 (6.4) 3/8 (9.5) 7/16 (11.1) 3/4 (19) 1/4 (6.4) 1/2 (12.7) 5/8 (15.9) Source: GANA Glazing Manual Tbl. 9 Recommended Joint Width for Butt-joint Glazing Glass Thickness, in. (mm) Joint Width, Min., in. (mm) Joint Width, Max., in. (mm) 3/8 (10) 3/8 (10) 7/16 (11) 1/2 (12) 3/8 (10) 7/16 (11) 5/8 (16) 3/8 (10) 1/2 (12) 3/4 (19) 1/2 (12) 5/8 (16) 7/8 (22) 1/2 (12) 5/8 (16) Source: GANA Glazing Manual


Three of the basic constraints for detailing are industry standards for sizes, material quality, and configuration of details. Common materials such as lumber, steel studs, panel products, and metal shapes are manufactured to standard sizes and shapes. In nearly all cases, these should be used as is, although some materials can be modified more easily than others.

E.g., it’s a fairly simple matter to trim a piece of lumber to a custom size but not possible to manufacture nonstandard metal studs. It may be possible to have a metal shop custom-fabricate a unique size of brass angle, but it’s less costly and faster to use a standard brass angle size. Proprietary products are often manufactured to fixed sizes, and these sizes are usually the basis for developing a detail that incorporates them into the design.

Standard methods of detailing can be found in references such as Interior Graphic Standards and Architectural Graphic Standards. Refer to Appendix A for a list of industry standards for material qualities.

Some common sizes of substrates are given in Tbl. 1. In addition, limiting sizes of metal partition framing, glass, and ornamental metal are often constraints when developing custom details. The sizes and shapes of common metal framing components are shown in ill. 3.

Constraints of glass detailing are shown in ill. 4, and values are given in Tbl. 7, 8, and 9.

Details utilizing ornamental metal are least costly and most efficient if standard shapes and sizes are used. Some of these for stainless steel and brass and copper alloys are shown in ill.5 and 6, and sizes given in Tbl. 10 and 2-11.

ill. 5 Standard stainless steel shapes (a) channels and angles (b) tubing round tubing square tubing rectangular tubing

ill. 6 Standard brass shapes (a) channels and angles (b) bar stock (c) tubing equal unequal equal legs unequal legs rectangular bar square bar rod round tubing square tubing rectangular tubing web flange

Tbl. 10 Standard Sizes of Common Stainless Steel Shapes Channels, in. (mm) Square Tubing, in. (mm) Tubing, in. (mm) Flange Web Thickness Angles, in. (mm) Size Thickness Rectangular Round


Although an almost unlimited number of details can be developed using standard materials, each does have its own advantages and disadvantages that the detailer must understand to use them effectively. Many products have withstood the test of time, and their quality and characteristics are well known and documented. Newer materials should be reviewed carefully and their qualities documented with standardized tests or individual manufacturer's tests to verify that they will serve the intended purpose. The manufacturer is the best source for detailed information on any particular product. However, for a more objective evaluation, trade associations and designers who have already used a new material are good sources to consult. When determining which materials or products to use in a detail, the following criteria should be reviewed.

Aesthetic Qualities

Aesthetic qualities are the characteristics that contribute to the design intent of the detail, as reviewed in Section 1. These qualities either contribute to the overall design concept of the space, resolve problems of connection or transition, visually coordinate with adjacent construction, or ful fill some combination of these three purposes.

Depending on the particular material or product, aesthetic qualities include color, texture, scale, proportion, shape, line, form, light reflectance, and any number of unique qualities specific to the material. The designer must make selections based on aesthetic qualities, while considering the other functional and practical aspects of the material. Some manufacturers or product lines may have a wider range of choice than others, and this fact alone my sway the decision to use a particular company or material.


Acoustic qualities of a material relate to the material's ability to absorb sound or to block the transmission of sound. For most finish materials, sound absorption is the more important criterion and is typically measured with the sound absorption average (SAA) or the previously used noise reduction coefficient (NRC). For open-plan office design, the articulation class of ceilings may also be important. For details of barriers, such as partitions, doors, glazing, and ceiling assemblies, sound transmission is important and may factor into the configuration of the detail.

Installation method is the precise sequence of steps needed to place the material or product into the work. Installation method can affect the cost and scheduling of a material and whether skilled workers will be required or not. In most cases, installation methods for the same types of materials will be very similar. However, some specialty items may require a particular method using factory-approved installers.

Refer to Section 3 for a full discussion of functional requirements of details.

Tbl. 12 VOC Limits for Interior Materials Volume Limits, g/L (lb/gal) Material EPA Limits California Limits a Green Seal Limits Flat, interior paint 250 (2.1) 50 (0.42) 100 (0.84)

Nonflat, interior paint 380 (3.2) 50 (0.42) 150 (1.26)

Interior stains 550 (4.6)

100 (0.84) 250 (2.10) Clear wood finishes, varnish 450 (3.8) 275 (2.31) 350 (2.94) Clear wood finish, lacquer 680 (5.7) 275 (2.31) 550 (4.62) Multicolored coatings 580 (4.8) 250 (2.1) Carpet adhesives 50 (0.42) 150 (1.26)

Wood flooring adhesives 100 (0.84) 150 (1.26) Ceramic tile adhesives 65 (0.55) 130 (1.09) Drywall and panel adhesives 50 (0.42) Multipurpose construction adhesives 70 (0.59) 200 (1.68) a South Coast Air Quality Management District (SCAQMD) Rules 1113 and 1168.

Effective 1/1/10 with colorant added at the point-of-sale.

EPA limits for clear and semitransparent stains. Opaque stain limits are 350 g/L (2.9 lb/gal).

For carpet pad only.

In California the Collaborative for High Performance Schools (CHPS) maintains a low-emitting material list.

Safety and Health

Safety relates to the prevention of accidental harm to people, as well as to security from intentional harm. Health covers a wide variety of topics, from mold resistance to indoor air quality.

Finish safety relates to the surface and edge condition of products. There should be no sharp projections, edges, or surfaces rough enough to cut or abrade people when they come in contact with the exposed portions of the detail.

Flammability, the likelihood that a material will combust, is one of the most important criteria for material and finish selection. Regulatory requirements for flammability is discussed in a separate section of this section.

Mold and mildew resistance of a material is important to prevent the growth of these microscopic organisms. Many materials are inherently susceptible to the growth of mold or mildew because they provide an organic nutrient that, when combined with moisture and a suitable temperature, will provide a growing medium for these biological contaminants. Most materials can be treated to resist the growth of mold and mildew.

Outgassing is the release of toxic gasses from materials, most commonly after the material has been installed. These gasses include formaldehyde, chlorofluorocarbons (CFCs), and others listed on the Environmental Protection Agency's list of hazardous substances. Outgassing is one of the important components of indoor air quality. Refer to Section 3 for a discussion of sustainability issues.

Security is providing protection against theft, vandalism, intentional physical harm, or a combination of all three. If security is an important aspect of a design, material and product selection can be evaluated in terms of this. Doors, glazing, and hardware are common products that are available with various levels of security.

Slip resistance is the ability of a flooring material to help prevent accidental slipping. It’s commonly measured with the coefficient of friction (COF). The COF is a measurement of the degree of slip resistance of a floor surface and ranges from 0 to 1. The higher the COF, the less slippery the surface. Although both the International Building Code and the Americans with Disabilities Act require flooring to be slip resistant, there are no specific requirements for the COF.

Many variables affect slip resistance, including wet versus dry conditions, shoe material, a person's weight, the angle of impact, stride length, and floor contamination. Numerous tests have been developed to measure the COF accurately and consistently, while accounting for the slip-resistance variables. These ASTM tests are listed in Appendix A. One of the most commonly used tests is ASTM D2047, Standard Test Method for Static Coefficient of Friction of Polish-Coated Floor Surfaces as Measured by the James Machine. This test is considered by many to be the most accurate and reliable measurement of slip resistance. However, it can only be performed in the laboratory on smooth, dry surfaces. It should not be used for wet or rough surfaces.

When using the James Machine test, a COF of 0.5 has generally been considered the minimum required for a slip-resistant floor. Underwriters Laboratories requires a level of 0.5 or higher as a minimum safety level based on the ASTM C1028 standard. The Occupational Safety and Health Administration (OSHA) also recommends a COF of 0.5 as a minimum.

Some have suggested a level of 0.6 for a good slip-resistant floor. In any case, when developing

flooring details and specifying slip resistance, the designer must refer to the specific test being used.

As stated earlier, the Americans with Disabilities Act requires that a floor surface be slip resistant, but it does not give any specific test values. However, an appendix in a hand guide for the ADA recommends a static coefficient of friction of 0.6 for accessible routes and 0.8 for ramps.

Until specific, uniform criteria are established, the designer should take into account the conditions under which flooring materials will be used before selecting a particular type of floor and incorporating it into a detail. E.g., a public lobby where snow and rain may be tracked in may need to be more slip resistant than a residential bathroom, where people are taking smaller strides without slippery shoe material.

Volatile organic compound (VOC) emissions result when chemicals that contain carbon and hydrogen vaporize at room temperature and pressure. VOCs are found in many indoor sources such as paint, sealants, and carpeting as well as many cleaning products. When selecting a material, its VOC content must be limited to the applicable standards. Tbl 2 gives some VOC standards from various organizations. Refer to a discussion of VOCs.


Durability relates to the serviceability of the product or material when in use. There are many aspects of durability, and one or more of these may apply to a particular detail. The following list gives some of the more common aspects of durability. Most of them have associated ASTM or other recognized standards that describe how they are measured and applied to products.

Some standards are specific to a particular type of test, while others apply to a particular type of material. E.g., durability standards for wall coverings are covered in ASTM F793, Standard Classification of Wallcovering by Durability Characteristics.

Abrasion resistance is the ability of a material or finish to resist being worn away or to maintain its original appearance when rubbed with another object. Abrasion resistance can be measured according to several standard test methods.

Attachment is the method by which one material is connected to another. This criterion can have a significant influence on product selection, depending on the substrate. Some products or materials cannot be attached to other materials or can only be attached with significant expense or extra effort. Attachment is one criterion that applies to nearly all materials and that must be reviewed as part of a systematic view of the entire detail of which the material is a part. Connection methods are discussed in more detail.

Breaking strength refers to the load that, when placed on a material, is just great enough to break the material. In interior design, it typically refers to fabrics and other textiles where the load is applied in the plane of the material, with the material laid flat. It may also apply to tile, stone, and other materials subjected to a localized load.

Chemical resistance is a material's resistance to damage, change of finish, or other deleterious changes resulting from exposure to chemicals. Because there are so many possible combinations of chemicals and finishes, most manufacturers specifically state which chemicals their products are resistant to.

Coating adhesion refers to the ability of a thin coating, like wall covering or paint, to adhere to its substrate.

Colorfastness is the resistance of a finish to change or loss of color when exposed to light, most commonly the ultraviolet light of the sun.

Corrosion resistance is a product's resistance to deterioration by a chemical or electrochemical reaction resulting from exposure to moisture, chemicals, or other elements. Corrosion is typically a problem when metal products are exposed to moisture.

Fabrication quality is the measure of how well a product is assembled in the factory. Each industry establishes measures of fabrication quality. E.g., woodwork is measured ac cording to three grades-economy, custom, and premium-as established by the Architectural Woodwork Institute's (Awe’s) Architectural Woodwork Standards.

Heat-aging resistance is a wall covering's resistance to the deterioration caused by high temperatures over an extended time.

Scrubbability is a material's ability to be cleaned repeatedly with a brush and detergent.

Stain resistance is a material's resistance to a change in appearance after the application and removal of another material. As with chemical resistance, all products are resistant to some staining agents more than others, so the manufacturer's literature should be consulted to verify if a material is resistant to staining agents likely to be present in a particular application.


Maintainability is an important quality for finish materials, products, and details that experience wear and tear through the life of a building. All buildings and interior finishes need to be maintained to preserve their appearance and service life. Many durability criteria directly relate to maintainability; the more durable a material is, the less maintenance is required.

Cleanability refers to the ease with which a material can be cleaned using whatever methods are appropriate for the material. E.g., carpet must be easy to vacuum, while wall finishes in a restaurant should be easy to wash. Because all materials in all types of buildings get dirty with time, cleanability is one of the most important criteria to consider when selecting finishes and incorporating them into a detail.

Repairability is a product or material's ability to be repaired when damaged. The ability to replace damaged components of a detail may also be evaluated when selecting a product.

The designer should avoid details that make it difficult or expensive to repair or replace one of the component parts.

Resilience is a material's capacity to recover its original size and shape after deformation caused by some load. Resilience is typically applied to soft floor covering material, such as vinyl tile but may also be an important consideration for wall details that incorporate soft covering materials.

Self-healing quality is a material's ability to return to its original configuration after it has been deformed or temporarily changed. It’s similar to resilience but may apply to any type of product. E.g., the holes in a corkboard should be self-healing after pins have been removed.

Cost and Delivery: Time Cost of a detail, as it relates to overall project budget, was discussed in a previous section.

However, when looking at a detail individually, it’s important to look at the cost of the detail in proportion to the total cost of the project. If the entire project is going to cost $3 million, it does not make sense to spend a great deal of time and worry over saving $100 on one detail.

On the other hand, if research and study on a typical wall detail of the same building can save

$30,000, then it’s reasonable to make the effort. In another situation, saving a little money on quantity items is desirable. If just $100 can be trimmed from the construction cost of one door detail that occurs three hundred times, then saving this amount will add up to $30,000.

Also, as previously discussed, the availability and delivery time of components of a detail may affect how the designer develops a detail.

Sustainability : Sustainability can be viewed as a constraint if there are local, state, or federal regulations concerning aspects such as energy use, volatile organic compounds, indoor air quality, and the like. E.g., California has very strict regulations on VOCs, lighting, and other aspects of energy conservation. However, in most cases, sustainability should be viewed as a basic function of any detail, even absent governmental regulations. Refer to Section 3 for a discussion of sustainability issues as a functional requirement.

Previous: (Process of DESIGN and DETAILING)
Next: FUNCTION of Interior Design

top of page | Home