Commercial Carpet Specification
January 22, 2008
Strecth-In Over CushionIn the commercial carpet installation field, installers are faced with the task of installing products that are doomed to fail regardless of the amount of skill used during the installation process. These failures occur mainly because an improper installation technique has been specified.
Architects and specifiers are usually the ones responsible for selecting the method by which a particular project is installed. On occasion they either misunderstand the product, installation method, local conditions or all of the above.
There are various reasons for selecting the method of installation on projects, following are but a few; carpet construction, local conditions, anticipated usage of the area, time constraints, budget, and aesthetics.
Following are explanations of the major installation techniques currently used for broadloom and modular carpets in the commercial field:
Direct-Glue DownCarpets installed with this method are glued directly to the substrate using either the trowel method or a spray system. Seams are secured by the use of a seam sealer. This is probably the least expensive method of installation available. Special attention must be paid to moisture and pH. It is important to specify carpets with an increased tuft bind that are constructed with unitary or specialized backings. This will reduce problems with seam raveling and tufts pulling out. If cushion is desired, carpets with attached cushions are available. In an occupied area, some people may find adhesive odors objectionable, even though most adhesives are designed to emit low odor and minimal VOCs.
Carpet modules or tiles are available that offer the feeling of a cushion and the integrity of a direct-glue installation without the adhesive odor. Future removal of direct-glue installations may be labor intensive, depending upon the type of adhesive used and the backing of the product.
Double-Glue InstallationHigh-density cushion is adhered to the substrate using pressure-sensitive adhesives. The carpet is glued to the cushion using premium adhesives. Seaming for double-glue installations can be specified either utilizing the hot-melt tape method or a chemical seam sealer method. CFI recommends that all seams be taped to avoid future problems.
Moisture and pH limits are critical to success. Quantitative testing should be performed prior to installation. The use of special pressure sensitive and premium adhesives drive up the initial cost of installation. The double-glue method is the most expensive from a labor standpoint. Installers experience “down-time” waiting for the pressure-sensitive adhesive to dry completely. Also, add the additional time waiting for the premium adhesive to flash-off before the carpet can be installed to minimize absorption into the backing. As adhesives are used to secure the products to the floor, the same problems that exist on the direct-glue installations in occupied areas can occur.
In addition to potential odor problems, double-glue installations require that traffic be limited for a minimum of 24 hours after installation. The quality of carpet selected for this type of installation is also critical to the success of the project. If the secondary backing of the carpet is tufted, it must be a minimum of 10-pick to allow for structural stability and reduce the possibility of SBR “fallout” caused by flexing of the backing during usage. Although release adhesives are used during installation, future removal will probably require the use of a floor stripper machine and could run into considerable cost.
Modular Carpet InstallationsModular carpets are intended to be installed using pressure-sensitive adhesives either full spread or the grid and perimeter methods. Manufacturers also have developed a “peel-and-stick” method that requires the use of a primer prior to installation. Though the initial cost of carpet tiles (modular carpets) appears to be higher, if extended over the “life expectancy” of the installation, this method has proven to be more cost effective in many ways. Reduced costs for repairs and the possibility of rotation of the carpets to extend the life by reducing traffic patterns in effect lower the cost by extending the life expectancy. Currently, carpet tiles are available with attached cushions. If replacement is to be with carpet tiles, the cost will be lower as the existing adhesive is reusable. However, if replacement with broadloom is expected, the cost will be somewhat higher as the adhesive will need to be isolated prior to replacement.
Consideration of the Installation TechniqueAll techniques are dependent on the local conditions at the time of installation to ensure success. Temperature and humidity must be controlled; traffic must be reduced and in some cases, eliminated for a specific amount of time. In the case of pattern installations, the job schedule must follow a specific order to guarantee matching of the patterns.
Utilizing the best installation skills on a project that has a wrongfully specified technique can and usually ends in installation failure. When faced with this dilemma, flooring contractors should require, and receive prior to starting, a job specific exemption from warranty on labor.
Other installation techniques are available, but the exotic nature of these techniques limits their amount of usage, and thus are not discussed here.
In order to provide the best outcome on any project, the entire scope of that project must be considered when specifying installation techniques.
When Should Installation Over Cushion Be Specified?In areas that require the use of a cushion, but are limited in size. Individual offices and small areas lend themselves to this style of installation and areas that are considered “light commercial” with limited traffic and no wheeled traffic may also use this method.
If moisture or pH is a concern, but not excessive; the use of synthetic cushion and carpets may be utilized. Their porosity allows for vapor emissions to escape, and pH will have limited effect.
When odors from adhesives may cause disruptions.
On projects where installation noise can be tolerated to mask substrate imperfections.
If immediate occupancy of the areas installed is a concern.
This method MUST be used with certain carpets depending upon construction. Example: Carpets constructed on a Wilton loom.
Installation over cushion may be used in the case of “temporary installations,” as damage to the substrate will be minimal.
Alternatives to the Stretch-in Over Cushion Installation MethodDouble-glue
Direct-glue of attached-backed products.
When Should the Direct-Glue Method Be Specified?Areas that are to receive heavy foot and wheeled traffic.
If a high tuft bind is required, utilizing this method of installation with a unitary-backed product is recommended. This method of installation will enable a faster installation if time constraints are a consideration on the project.
From a budgetary standpoint, this is usually the most cost-effective method of installation. Design capabilities are increased at a lesser cost due to the increased speed of installation.
The possibility of pattern alignment is enhanced with this method. ONLY if the substrate meets requirements for vapor emissions and pH levels based upon the ASTM methods of testing.
When Should Double-Glue Be Specified?Projects that require the use of a cushion; but need to eliminate the possibility of wrinkling.
Large areas where an installation over cushion may fail.
Areas that are to receive heavy traffic, both foot and wheeled, and require the use of a cushion.
On projects where time and budget are of minimal concern.
Alternatives to Double-Glue InstallationsAttached-cushion carpets installed via the direct-glue method.
Installation over cushion if the areas to be covered meet the criteria.
When Should Modular Carpets Be Used?Projects that expect excessive soiling and staining may find modular carpet installations the better choice as they allow for easier replacement.
If traffic patterns are expected to develop, tiles can be rotated to allow for even wear.
On projects that require exceptional tuft bind qualities.
Projects with partitions and other demountable accessories will find modular installations more reasonable from a cost standpoint.
Modular installations allow expanded design capabilities.