To Stretch or Not to Stretch
In the forties and fifties, the favored installation was rugs or loose-lay carpet, tack-down carpet or linoleum. In the sixties, demand for carpet in homes was booming and installers who worked for contracting firms or work rooms began taking installation jobs over the weekend. Most of the jobs were wall-to-wall jobs over tackless. Many of the installers did not have stretchers, so they used their kickers to stretch the carpet over the tackless pins.
Today, a lot of carpet is still installed with a kicker by independent installers who work out of their truck at low-end prices. This is the exception instead of the rule, but corners are cut from time to time by fast and cheap carpet layers.
Many organizations are involved today in installation training, and contractors adhere to industry standards. The Carpet and Rug Institute (CRI), industry unions and installer associations promote quality installations to assure that the carpet installation the consumer purchases will provide customers with quality installations. The CRI publishes the Carpet Primer, which, among many other details, has a section on carpet installation. Following are some excerpts from the section on carpet installation methods. The two predominant methods of installation are stretch-in and glue-down.
In stretch-in installations, the carpet is stretched using a power stretcher over a separate cushion and held tightly in place with tack strips mounted around the edge of the room. To get the required tension in any size area, use of a power stretcher is required. This stretch-in method is most commonly used in residential installations but can be a part of many commercial installations.
Some advantages of the stretch-in method are:
• Ease in pattern matching
• Can be used over floors unsuitable for glue-down
• Corrective measures, such as seam repair, may be easier to perform
• Removal costs are usually less than the removal of an adhered installation
Stretch-in installations should be avoided:
• On ramps and inclines
• Where office systems furniture and moveable partitions are utilized
• Where heavy rolling traffic is likely
• When carpet has a unitary backing or other backing systems designed only for glue-down installation
Here are the keys to successful stretch-in installation:
• Sufficient tension applied and maintained on the carpet
• Cushion selection that meets the carpet manufacturer's requirements of thickness and density
• Carpet seams correctly trimmed, edges properly secured or sealed with the required seam adhesive, and seam placement conforming to approved shop standards
• Proper environmental conditions maintained before, during and after installation
Tack strip is the most widely used fastening device to maintain tension. There are several types of tack strip, each with a specific use. For example, commercial strip with three rows of pins is used when dimensions exceed 30 feet. Alternately, double stripping, using two rows of standard strip, may be used.
Regardless of the anchoring method, the strip must be installed with pins facing the wall, leaving a space between the wall and strip (gully) slightly less than the thickness of the carpet, but no more than 3/8-inch.
Glue-Down Carpet Installation
The most widely used method of installing carpet in commercial areas is with adhesives. Carpet with or without an attached cushion or separate cushion can be installed in this way. There are two basic types of adhesive methods: direct glue-down and double glue-down.
In direct glue-down (carpet may be with or without an attached cushion), an adhesive is used to bond the carpet to the floor. Double glue-down is a method whereby carpet cushion is first adhered to the floor, and then the carpet is adhered to the cushion.
Reasons for Specifying Direct Glue-Down Installation:
• Functions well for rolling traffic and ramp areas
• Provides more durable seams since there is no vertical flexing
• Minimizes carpet buckling in buildings that have HVAC systems turned off for extended periods of time
• Practically eliminates incidences of seam peaking
• Creates no restrictions for area size
• Offers intricate border and inlay possibilities
• Usually is less expensive
Reasons for Specifying Double Glue-Down Installation:
• Combines the stability of direct glue-down carpet with the cushioning benefits of a separate cushion, stretch-in installation
• Improves carpet appearance retention, foot comfort and overall performance
• Simplifies carpet bordering and inlaying
• Functions well for wheeled traffic areas
• Creates no restrictions for size of area
Seams should be prepared according to the carpet manufacturer's recommendations, using appropriate seam cutting tools. Seam edges should be protected with the appropriate seam adhesive to prevent fraying and raveling, unless otherwise directed by the manufacturer's recommendations.
The specific amount of adhesive must be applied to the floor to obtain the required 100 percent adhesive transfer onto the carpet back. The quantity applied is controlled by the size of notches in the installer's trowel. If too little adhesive is used, the long-term integrity of the bond will be compromised.
For the purposes of improved indoor air quality, low-emitting adhesives (adhesives without a solvent base) are available. When coupled with CRI guidelines for ventilation, these low-emitting adhesives will improve indoor air quality conditions, both for the installer and the building occupants.
When field-applied, glue-down installations are used, allowing traffic too soon can cause installation failure. Traffic should be restricted for a minimum of 24 to 48 hours to allow proper adhesive cure. However, some manufacturers recommend restricting traffic for an extended period.
To facilitate move-in, protect the installation from rolling traffic by using sheets of hardboard or plywood in the affected areas. Craft or rosin paper can be used to protect installations from soil and/or light traffic, but never use plastic sheeting, as the curing of the adhesive will be adversely affected, resulting in the growth of mold or mildew. Exposure to water from cleaning or other sources should be restricted for a minimum of 30 days after installation.
Installing Carpet Over Carpet
Carpet contractors are sometimes asked to install new carpet over old carpet. Unless it's the manufacturer's specific recommendation, carpet should not be installed over existing carpet.
Effective stretching is retarded by the drag of the old carpet pile. In addition, flexing of the old carpet pile under traffic stretches the new carpet and creates bubbles. The new carpet traps existing oil, bacteria and contamination that may be present in the old carpet.
Finally, the additional layer of carpet may result in the new carpet system not meeting fire and building codes.