Asumag 625 Shutterstock31456222 Library Reference Room

Carpet Specification

Nov. 1, 1998
Tips for specifying carpet in schools.

Certain issues need to be addressed in order to specify carpet, regardless of the type of installation site. The specifier needs to determine the expectation for the carpet and which of the selection criteria are most important. The following basic issues should be considered to determine carpet specification:

-Aesthetics: color, texture, design/pattern, luster and appearance.

-Appearance: durability, wearability, cleanability, installability, color retention and fastness, texture retention, appearance retention, etc.

-Functionality: flammability, static propensity, indoor air quality, acoustical value, insulation, value, etc.

-Cost: initial product cost, installation, maintenance, disposal, life cycle.

-Government or building code requirements.

There are two types of carpet specifications: construction and performance. Construction specifications tell the manufacturer in very precise terms how the carpet is to be made (look, size, weight and manufacturing of raw materials and processes) without directly stipulating performance needs or end-use requirements. A construction specification would include the following:

-Construction type: tufted, woven, knitted, needlepunched, etc.

-Construction materials: fiber (fiber type, size), backing (type, weight) and adhesives.

-Construction methods: yarn manufacturing (yarn size and ply), fabric formation (gauge, pile height and texture, density, total weight), coloration techniques (dyeing methods), finishing and treatments.

-Product characteristics: texture, color/design, size/type and functional enhancements.

Common errors in construction specifications are either to under- or over-specify. When too many minor details are included, there is a tendency to specify beyond the possibilities of the manufacturer or to limit the flexibility of new technology. The specification for yarn size might be too large for a particular gauge, or the yarn size, gauge, stitch, pile height and weight might be impossible to create in the specified combination. There also is a tendency to perceive that more is better-more pile weight, more plies, more rows, etc., mean better durability. Each of these does play a role, but the "more" perception may not relate to better performance or product.

Another consideration is that with current manufacturing technology and anticipated technological developments, many of the standard terms may not apply today. For instance, air-entangled yarns are really not plied; therefore, twist per inch does not have the same meaning as for twisted yarn. Scrolling, shifting, eccentric or pattern tufting machines provide mixed gauges and stitches and, with overtufting, even changing gauges.

Construction specifications should be used to describe the overall look of a product and not be so detailed as to limit the manufacturer from making a quality product.

Important factors

One of the most important, and often most misunderstood, factors in a construction specification is density. Density is simply the index of how much yarn is packed into a given volume or area. The larger the density value, the more compact the pile, which yields a firm walking surface.

Density can be an important determinant of carpet performance-especially for high-traffic environments. Density is influenced by many factors, such as stitches per inch, yarn thickness, gauge and tuft height. Gauge is more a function of yarn size: a "fat" or larger size can be tufted at a wider gauge, or smaller yarns at a tighter gauge, and receive the same density rating. Specifiers who understand the various factors affecting density have a greater chance of specifying the best carpet performance for a given budget.

There are various methods of stating relative density specification for pile carpet. Average pile yarn density (APYD) is the most common and useful decision tool used in conjunction with other carpet specifications. It is determined by pile weight (specified in finished ounces per square yard), pile thickness or tuft height. Pile thickness and tuft height are laboratory means ofdetermining what is commonly known as pile height. Pile height is sometimes measured with a small ruler or dipstick, but these only make rough determinations and should not be considered accurate.

Note that while other approaches quantify density, APYD usually is adequate. Generally, the higher the APYD value, the better the expected carpet performance, once other important factors are considered. Average pile yarn density for quality commercial carpet will normally exceed 4,000, while high-demand usage may require an APYD of more than 6,000. Other factors indirectly help determine density, such as the number of tufted rows across a unit width and the number of stitches per unit length of each tuft row.

In tufted carpet, gauge, or the reciprocal of the number of tuft rows per inch of width, is a major density factor. For example, a 1/8-gauge carpet has eight tuft rows per inch of width and a 5/32-gauge carpet has 6.4 rows per inch of width.

When comparing density, look at the whole picture. In theory, a 1/8-gauge carpet should be more dense than a 5/32-gauge carpet. However, other factors, such as yarn size and pile thickness, come into play and will have a great effect on the pile density of the product.

For woven carpet, the equivalent of gauge may be obtained by dividing the pitch (number of ends of yarn in 27 inches of width) by 27 inches.

The number of stitches (tufts) per running inch of carpet usually is specified directly for tufted carpet, but is called rows per inch for woven carpet. The numerical product of tuft rows per inch of width multiplied by stitches per running inch is the number of tufts per square inch, or tuft density.

Additional factors

Other factors that affect carpet performance include yarn size and characteristics. Yarn twist and proper heat setting are of utmost importance for cut-pile styles. A low twist, or poorly heat-set yarn in a cut-pile carpet will tend to mat, tangle and appear worn.

Other quality determinants often written into construction specifications are the backing systems used, the type of fiber, whether the yarn is spun or continuous filament, and the dye method used.

Although not considered descriptive of quality or performance, total finished carpet weight is sometimes included in specifications. It should not be confused with pile yarn weight. Total finished weight includes all backing materials, latex, foams, topical finishes and face yarns. Like pile yarn weight, total finished carpet weight is expressed in ounces per square yard. It is primarily used as an indication of roll weights.

Construction specifications can be proprietary, identifying a specific carpet by grade, name and manufacturer. An "or equal" specification also could identify a specific grade, listing its construction factors so that other manufacturers can bid for the order competitively. In this case, the usual procedure is to approve "or equals" in advance of the actual bidding. Full attention then can be given to price and delivery information when bids are analyzed.

Avoid over-specifying. As new technologies emerge, construction specifications will become less important, especially as performance estimators. Appearance is simply an aesthetic choice, while appearance retention truly is a performance issue. Therefore, performance specifications will likely increase in the future.

Performance specifications Performance specifications detail the necessary performance attributes, telling the manufacturer how the carpet must perform without detailing how it must be made. Specifying performance rather than construction can take the difficult pressures off the specifier to provide accurate details and is safer for the specifier who is not familiar with the latest carpet technology and materials.

A typical performance specification for carpet might include the following:

-Functionality factors, such as


-Delamination resistance.

-Colorfastness-light, crocking (rubbing), water bleed.

-Static propensity.

-Acoustical information.

-Moisture penetration.

-Stability to moisture.

-Appearance retention and wear properties as defined by the specification. An example would be soil resistant treatment.

-Indoor air quality emissions requirements.

-Safety/regulatory requirements, including flammability, smoke density, combustion toxicity (New York State), ADA requirements.

The creative factors-pattern, color, texture-which are properly and exclusively the province of the carpet designer or decorator on the job, also are major contributing factors in the specification.

Specifiers should be aware that specifying performance for special order or custom-made carpet rather than for in-stock grades can create some unanticipated delays. In the case of a custom order, the specifier must allow time for development and testing against performance criteria. Not only must the manufacturer have time to develop the basic construction, trial samples must be tested to be sure they perform as expected. The time involved may run considerably longer than typical specifying and bidding periods allow.

Requirements for inclusions

Whether written for construction or performance, most carpet specifications should incorporate requirements governing the following items:

-Installation procedures and accessories. (Follow manufacturer's recommendations and/or Standard for Installation of Commercial Textile Floorcovering Materials, CRI 104 or Standard for Installation of Residential Textile Floorcovering Materials, CRI 105.)

-Qualifications of the installation contractor (Floor Covering Installation Board certified or certified by the manufacturer).

-Type of installation (stretch-in, glue-down or alternative methods).

-Cushion type and weight.

-Certification that materials meet federal, state and local government ordinances for flammability and ADA requirements.

-Delivery and installation schedules.

-Carpet maintenance (request manufacturer maintenance instructions).

-Government specifications and regulations.

-Special installation instructions for patterns, unusual shapes, borders, etc.


-Guidelines for IAQ.

Specifying installations

Two of the most important factors in completing the specification are stipulating installation procedures and cushion requirements. There are two main types of commercial carpet installation methods: stretch-in and glue-down. In some cases other types of installations may be used, such as double glue-down and alternative-type methods. There are several factors to consider before making a decision regarding installation type, including:

-The load and nature of the traffic. Direct glue-down generally is specified where rolling equipment and heavy traffic is expected.

-Necessity of partial installation, such as when the workplace is occupied or installments.

-Type and condition of the sub-floor. Especially important for glue-down installation on concrete slabs.

-Dimensional stability. Heavy use on large, open areas can cause dimensional movement, buckling and stretching of stretched-in carpet.

-Ventilation during installation.

Flammability requirements

All carpet and rugs 4 ft. x 6 ft. (122 cm x 183 cm) or larger must meet the requirements of FF1-70 (flammable fabrics) as found in 16 CFR 1630 (Code of Federal Regulations). This requirement, under the jurisdiction of the Consumer Product Safety Commission (CPSC), states that no more than one out of eight specimens shall burn a distance of 3 inches from the point of ignition when tested according to the prescribed method.

The test method, known as the "pill test," involves subjecting a 9 inch x 9 inch specimen, which has been dried in an oven, to the flame from a standard igniting source in the form of a methenamine tablet. The tablet, or pill, is placed on top of the pile in the center of the specimen and ignited with a match, providing a standardized flame source for a period of about two minutes. If the flame is spread by the carpet more than three inches from the point of ignition, the specimen fails; and if more than one specimen of eight fails, the style of carpet cannot be legally manufactured for sale. The burden of compliance with FF1-70 rests with the carpet manufacturer.

The flooring radiant panel test method evaluates the tendency of a floor system to spread flame when exposed to the radiant heating of a gas-fired radiant panel. The method determines a material's critical radiant flux, or the minimum radiant energy a fire needs to sustain flame propagation of the flooring system measured in watts per square centimeter. The flooring radiant panel apparatus involves a 100 cm x 20 cm, 39 inch x 8 inch sample mounted horizontally on the floor of the test chamber.

The specimen receives the radiant energy exposure from an air-gas fueled radiant panel mounted above the specimen. The gas-fired radiant panel generates a radiant heat-energy exposure along the length of the specimen ranging from a maximum of approximately 1.1 watts per square centimeter immediately under the radiant panel, to approximately 0.1 watts per square centimeter at the far end of the test specimen. A gas-fired pilot burner is used to initiate flaming of the sample.

The test is continued until the specimen ceases to burn. The distance the flooring system burned is noted. The level of radiant heat-energy exposure is noted at the point the flooring system self-extinguished. This measurement is reported as the sample's critical radiant flux, or the minimum energy necessary to sustain flame propagation.

Following are CRI recommended critical radiant flux limits for specific installations where automatic sprinkler protection is not provided:

-Class I-average minimum 0.45 watts per square centimeter within exits and access to exits (corridors) of health-care facilities (hospitals, nursing homes, etc.), and new construction detention and correctional facilities.

-Class II-average minimum 0.22 watts per square centimeter within exits and access to exits (corridors) of day-care centers, residence halls and apartment buildings. These limits are based upon comparison of performance of traditionally used materials and performance of flooring systems within full-scale corridor fire tests.

The flooring radiant panel test method is applicable to carpet installed in corridors and has no application to room installations.

Life-cycle costs

The life-cycle of the flooring system is referred to as the "use life" of that material before replacement. "Use life" is defined as the actual years carpet or other materials are used, rather than indicating when they are worn out. Flooring materials may be removed due to aesthetic renovation or during scheduled refurbishment of the facility.

Cleaning material costs and the cost of maintaining cleaning equipment are major variables in a life-cycle cost analysis. It generally is recognized that repair costs on hard-surface cleaning equipment are higher than the repair costs of carpet maintenance equipment. The cleaning involves higher speed moving parts and, thus, more equipment repairs.

The common perception is that carpet costs less at the time of installation, but over time, hard surface floor coverings cost less. However, for an accurate assessment of life-cycle costs, specifiers should base their analyses on total-use costs, taking into consideration the initial installed cost of the product, the length of the use life both in terms of durability and appearance retention, maintenance expenses including labor, supplies and equipment, and removal costs.


Several warranties commonly are offered by manufacturers as an assurance to the end users of long-term satisfaction and product performance. These warranties often are listed as part of the specification.

Common items typically covered by warranties are wear (loss from fiber abrasion), static propensity, tuft bind, edge ravel, dimensional stability, pattern match, staining and other non-specified latent defects. In most cases, the warranties are limited to a specific number of years, but in some cases, such as static, the warranty is, in effect, for the life of the product. Warranties should be reviewed carefully to determine the obligations of the end-user and the manufacturer.

Ensuring access

The Americans with Disabilities Act (ADA), which became effective January 26, 1992, is intended to ensure that people with disabilities have access to employment, public accommodations, government services, transportation, telecommunications and commercial facilities.

Ground and floor surfaces along accessible routes and in accessible rooms and spaces including floors, walks, ramps, stairs and curb ramps, shall be stable, firm, slip-resistant and shall comply with general requirements of ground and floor surfaces.

The carpet shall be securely attached; have a firm cushion pad or backing, or no cushion or pad; and have a level loop, textured loop, level cut pile, or level cut/uncut pile texture. The maximum pile thickness shall be 1/2 inch. Exposed edges of carpet shall be fastened to floor surfaces and have trim along the entire length of the exposed edge.

Changes in level up to 1/4 inch may be vertical and without edge treatment. Changes in level between 1/4 inch and 1/2 inch shall be beveled with a slope no greater than 1:2. Changes in level greater than 1/2 inch shall be accomplished by means of a ramp.

Specifying for good indoor air quality While there currently are no federal laws or regulations governing IAQ in commercial or institutional buildings, the federal government encourages builders, designers and manufacturers to adopt reasonable standards to ensure good indoor air quality. Although there are many factors that affect IAQ, one proactive way to ensure good air quality is to specify low-emitting indoor furnishings, building supplies and surfaces.

When specifying carpet, choose a product that bears the Indoor Air Quality Carpet Testing Program label. Under the program, carpet product types are collected from carpet manufacturers and tested quarterly for total volatile organic compounds (TVOC). Carpet products that do not exceed the established emission levels are allowed to display the label. The label has a number that identifies the manufacturer of the carpet. The label may be affixed to carpet samples and used in a variety of manufacturers' literature to architects, interior designers and specifiers. Using new carpet with the CRI label assures the specifier and the end user that the carpet is a low-emitting product, and its low emissions will have minimal impact on the indoor environment.

The following timeline will be an effective guide whether the installation is for a new facility or a replacement of carpet in an existing facility:

120 days before occupancy:

-Write specifications for carpet and installation.

-Request proposals.

90 days before occupancy:

-Review proposals.

-Check reference of carpet companies and installation contractors under consideration.

-Select company; place order.

-Prepare maintenance plan under the guidance of the carpet manufacturer.

60 days before occupancy:

-Confirm that order was placed with mill; confirm shipment date from mill.

-Schedule delivery, arranging for holding site.

-Confirm installation date.

30 days before occupancy:

-Check correctness of shipment: carpet style, color, pattern and dye lot.

-Check for manufacturing defects. (Note: Manufacturers will not replace carpet that has been installed.)

-Complete all other construction prior to installation to protect new carpet.

-Have carpet installed observing CRI 104/105 guidelines for installation.

-Ventilate during installation to protect indoor air quality.

-Have representative come to review punch list.

Sponsored Recommendations

Schedule an AIA Course Presentation

Get closer to completing your annual AIA Continuing Education requirement.. Our continuing education courses will get you that much closer to completi…