By Floorcovering Forensics Company
BOND FAILURE SYMPTOMS AND SOLUTIONS
Despite the carpet industry’s efforts to improve the quality of installation workmanship, bond failure in commercial carpet installations remains a leading cause of complaints, lawsuits and premature replacement. Annual losses from such failures run into the millions of dollars, and ripples and open seams caused by bond failure create a high-liability safety hazard.
This bulletin discusses the most common types of failure, their causes and methods of prevention. The highlighted boxes are selected quotes from applicable sections of the Carpet and Rug Institute’s CRI 104 Standard for Installation of Commercial Textile Floorcovering Materials.
CAUSES OF BOND FAILURE
The #1 Cause: Incorrect Trowel Size
By far the leading cause of bond failure in both direct-glue and double-glue installations is application of too little adhesive, usually resulting from use of a trowel that is the wrong size and/or too worn to provide 100% transfer of adhesive to the carpet.
INCORRECT OPEN TIME
Open time is the time allowed after spreading adhesive before carpet is laid into it. This time allows the adhesive to release some of its moisture and develop tack. Proper open time is critical, since too little open time may result in too much adhesive being absorbed into the back of the carpet, leaving too little between the carpet and floor or cushion. Allowing the adhesive to stand too long reduces its ability to bond to the back of the carpet.
MOISTURE AND ALKALI
Prolonged exposure to moisture and/or high alkalinity is detrimental to most adhesives. Unfortunately, the pH of moisture released by concrete often is as high as 12 to 12.5, more than 1,000 times higher than most adhesives can withstand. Alkali from within concrete is carried to the surface by migration of water from under or within the slab toward warmer, drier air at the surface. Depending on the porosity of the carpet, moisture emissions generally should be below 3-5 pounds per 1000 square feet per 24 hours as measured by the quantitative calcium chloride test. In addition to concrete, cleaning, if done improperly (allowing the carpet’s back to become saturated) or using excessively alkaline chemicals, can cause the adhesive to gradually deteriorate.
OTHER CONCRETE PROBLEMS
If the surface of a concrete slab is dirty, oily, dusty or contaminated with curing or parting agents, a secure bond cannot be established. Even the best workmanship cannot prevent failure caused by poor floor preparation.
All installation materials must be thoroughly acclimated before installation. Ideally the temperature and humidity at which the materials are conditioned should be similar to that under which they will be used. Though this often seems impractical due to construction schedules and site conditions, it is a very real factor in the success or failure of the installation.
Adhesive takes time to set up enough to withstand traffic. Premature traffic forces adhesive out from between the carpet and floor (or carpet and cushion) up into the carpet’s back, where it cannot provide bond strength.
If an adhesive is chemically incompatible with a carpet backing or cushion, adhesive deterioration and/or failure are almost inevitable. Though not a common cause of failure, it does occur, usually due to the wrong adhesive being used.
CUSHION PROBL EMS
Double-glue installation failures may occur when the surface of a cushion will not allow the adhesive to bond securely. In some cases, the cushion actually fractured within, leaving half glued to the carpet and half glued to the floor. This is particularly probable if the cushion used is unsuitable for the type and/or volume of traffic of the application.
If carpet is not properly pressed into the adhesive, it is unlikely that 100% transfer will be achieved. But if the carpet is rolled too much, or with a roller that is too heavy, the adhesive will be forced up into the recesses of the carpet’s back, resulting in a weak bond.