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 pose a high-liability safety hazard.

This article discusses the most common types of failure, their causes and methods of prevention. The quotes are from applicable sections of the Carpet and Rug Institute’s CRI 104 - Standard For Installation Specification of Commercial Carpet.

The #1 Culprit: Not Enough Adhesive

By far the leading cause of bond failure in both direct-glue and double-glue installations is application of too little adhesive. This almost always cause by use of a trowel that is the wrong size (figures 1 and 2) and/or too worn (figures 3, 4 and 5) to provide 100% transfer of adhesive to the carpet.

Select the appropriate adhesive and trowel notch configuration recommended by the carpet manufacturer and/or adhesive supplier, or refer to the list shown in Table II as a minimum.

—§9.3.1

Figure 3

The floor adhesive must be spread uniformly over the subfloor with an appropriate trowel, leaving ridges of sufficient height to achieve full and complete coverage of the substrate and carpet backing, including penetration into the backing’s deepest recesses. Trowel notches wear down during use. Maintain a clean and properly notched trowel throughout the installation process. After sufficient open time, the carpet must be pressed into the adhesive and rolled with an appropriate roller as specified in section 9.6.

—§9.3.2

Figure 4

When applying cushion to floors and carpet to cushion, select the appropriate adhesive and trowel notch size recommended by the carpet, cushion and adhesive manufacturer. If recommendations are not available, refer to the general minimum guidelines in Table II. Adhesive must be spread uniformly over the cushion with the specified trowel or other application procedure. After sufficient open time, the carpet is to be pressed into the adhesive and rolled with the appropriate roller. Proper open time is critical for a successful installation.

—§10.5

CRI 104, Table II - Trowel Size Minimum Guidelines

[insert table here]

Even with the correct sized trowel, too little adhesive may be applied if the trowel is used incorrectly. For example, holding the trowel at a 45-degree angle results in approximately 30% less adhesive being applied compared to the same trowel held at 90 degrees to the floor. Another bad habit is holding the trowel at an angle relative to the direction of travel. The trowel should be held perpendicular to the direction of travel; if it’s held at a sharp angle, too little adhesive may be applied.

Notes: The above guidelines should only be used when specific recommendations are not available from the carpet manufacturer and/or the adhesive supplier. Rough, porous concrete surfaces and heavily textured carpet backs may require a trowel with deeper notches than listed above. A 100% transfer of floor adhesive into the carpet backing while maintaining full coverage of the floor must be obtained.

Real world: Though 100% transfer is what the standard requires, installation don’t fail if the transfer is 80-90%. In fact, I don’t think I’ve ever seen a failure occur with a transfer of 70%. Installations that fail due to too little adhesive transfer typically have less than 50% transfer — often a lot less. In other words, if there’s so little transfer that the installation actually fails, it’s not even close to meeting the 100% transfer requirement.

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.

Open Time – Appropriate open time varies depending upon environmental conditions, subfloor porosity, backing system and adhesive type. Refer to the adhesive and/or carpet manufacturer for recommendations regarding open time.

—§9.3.3

Terrazzo, Ceramic, Marble, Slate and Other Nonporous Surfaces - Remove surface finishes and abrade flooring surfaces to ensure adhesion. Grout lines must be filled and flush with flooring material surface. Strict attention must be given to the “open time” recommendations of the adhesive manufacturer when adhering carpet to these surfaces.

—§9.2.4

Open Time - Adequate open time for adhesive must be allowed. Open time varies depending upon environmental conditions and the adhesive type.

—§11.3.2

Moisture and Alkali

Prolonged exposure to moisture and/or high alkalinity is detrimental to most adhesives. (Figures 6 and 7). 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.

Adhesive Installations - The owner or general contractor must have concrete subfloors tested to determine the moisture emission rate and surface pH prior to installation. (See Section 7.10.) CAUTION: Any concrete floor, even when adequately cured and dry, can allow moisture vapor to pass through to its surface. Depending upon the type of carpet and method of installation, the moisture emission rate greatly influences the long-term success of an installation. The use of a properly installed, uncompromised, approved moisture membrane is essential in preventing moisture migration into and through a concrete slab. (Ref. ASTM F 710.)

—§7.4.2

Testing Concrete Subfloors - Before making an adhesive-adhered installation, the owner or general contractor, or their designated testing agent, must submit to the flooring contractor a written report on the vapor emission levels and the surface alkalinity of concrete subflooring. Testing must conform to ASTM standards. Note: It is recommended that qualified independent testing agencies be used for determining vapor emissions and alkalinity in the floor surface. Testing by an independent specialist to determine installation suitability is a prudent and necessary safeguard for general contractors, owners, architects, flooring products providers and installation contractors.

—§7.10

Figure 7

Moisture Vapor Emissions Testing - Concrete floors, even with adequate curing time, can present an unacceptable moisture condition by allowing excessive amounts of moisture vapor to pass through to the surface. This can be a problem even on suspended concrete floors. Test all concrete floors for moisture emission rates using an anhydrous calcium chloride moisture test kit. This quantitative test method must be conducted carefully in strict compliance with ASTM Test Method F 1869. Moisture emission rate is measured in pounds of moisture over a 1000 ft2 area during a 24 hour period. Because calcium chloride testing requires a minimum of 60 hours to conduct, proper installation planning is required. As a general guideline, an emission rate of 3.0 lbs. (1.4 kg) or less is acceptable unless otherwise specified by the carpet manufacturer.

—§7.10.1

Testing for Alkalinity - A pH range of 7-9 is satisfactory; however, a reading above 9 requires corrective measures. Perform testing in accordance with ASTM Standard Practice F-710; or consult the adhesive manufacturer for recommended testing and corrective procedures. Note: The results obtained from testing reflect only the condition of the concrete floor at the time of testing. Further, it is highly recommended that the test site or building be at the same temperature and humidity expected during normal use. These conditions must be maintained 48 hrs prior to, and during testing.

—§7.10.2

Other Subfloor 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 can not prevent failure caused by poor floor preparation.

Figure 9a

Subfloors must be structurally sound and free of foreign substances that might compromise the carpet or its installation. Patching compounds must be suitable for the use application. They must be polymer-fortified and applied according to the patch manufacturer’s instructions. Note: Patched areas may be porous and highly alkaline, which may prevent adequate adhesive bond. For best results patched areas should be primed.

—§7.3

Figure 9b

Metal floors must create a smooth, even plane, and be cleaned of grease, oil, soil and rust.

—§7.6

Painted surfaces may be suitable for adhesive application; however, appropriate bond tests may be required. Contact the adhesive manufacturer for recommendations. Glossy surfaces must be abraded prior to installation.

—§9.2.2

Figure 10

There are a number of liquid adhesive removers available that effectively remove existing adhesive residue from sub-floors; however, there is evidence that some products may adversely affect the new adhesive or the new floor covering. Residues left in or on the concrete slab may cause failure of the new floor adhesive. These compounds may leave residue that interferes with adhesive bonding. They must not be used prior to adhesive application. Vacuum dusty areas instead.

—§9.2.6-7

Figure 11

Concrete surfaces must be clean, dry and free from excess alkalinity. Wax must be removed, and painted surfaces must be sanded thoroughly and cleaned before installation.

—§17.2.1

Painted wood surfaces must be roughened prior to installation. Slotted wood surfaces must be covered with an outdoor-grade plywood and primed with a primer that is compatible with the adhesive selected. Waxed or oiled wood surfaces present special problems and require resurfacing. Adhesive installations over pressure-treated lumber generally are not recommended. Contact the adhesive and carpet manufacturer for recommendations.

—§17.2.2

Metal surfaces must be cleaned of grease, oil, soil and rust, and they must be properly primed. Painted metal surfaces must be rough-sanded, with loose paint removed. Aluminum surfaces should be sanded immediately before applying adhesive.

—§17.2.3

Inadequate Conditioning

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.

Temperature and Humidity – Carpet must be installed when the indoor temperature is between 65-95ºF (18-35ºC) with a maximum relative humidity of 65%. If ambient temperatures are outside these parameters, the installation must not begin until the HVAC system is operational and these conditions are maintained at least 48 hours before, during and 72 hours after completion.

—§7.2

Relaxing/Conditioning Carpet – To minimize wrinkling and buckling, and to facilitate installation, it is highly recommended that carpet be unrolled and allowed to relax in the installation area for a minimum of 24 hours at a temperature between 65-95ºF (18 -35ºC).

—§7.11

Relaxation/Conditioning Carpet – Refer to Section 7.11. Site conditions, environmental and ventilation conditions become even more important when performing ouble-glue-down installations. In double-glue installations, a separate cushion is adhered to the subfloor and the carpet is glued to the cushion. CAUTION: Because significant differences exist in various carpet cushions, consult with the manufacturer of the cushion, carpet and adhesive for recommendations regarding this installation method. Only materials specifically designed for this installation method may be used.

—§10.1

Premature Traffic

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.

It is highly recommended that traffic over field-applied adhesive installations be restricted for a minimum of 24-48 hours to allow adhesives to cure properly. Premature trafficking can cause installation failure. Restrict carpet exposure to water from cleaning or other sources for a minimum of 30 days.

—§16.1

Material Incompatibility

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.

Wood that is chemically pressure-treated to alter properties relating to outdoor exposure or flame resistance may not be a suitable substrate. Floor covering adhesives could be subject to chemical degradation when applied to these surfaces; therefore, direct-glue installations on pressure-treated wood sub floors are not recommended.

—§9.2.1

It is not recommended that carpet adhesive systems be used directly over existing sheet vinyl, homogeneous or laminated solid vinyl tile, and some rubber flooring products. These materials may contain vinyl plasticizers that could migrate into the carpet adhesive and loosen the bond. … Soil, dust, wax, oil, grease, moisture and other contaminants can prevent or otherwise destroy adhesion causing localized or widespread failure.

—§9.2.3

Using primers on floor surfaces generally is not required except for sanded wood sheet products, dusty, porous or acoustical concrete surfaces. Priming cannot overcome moisture vapor emissions and must not be used for that purpose. They must be compatible with adhesives, which should be applied only after the primer is cured. Where lightweight or acoustical concrete subfloor is present, refer to manufacturer recommendations for the proper installation procedure to use before the carpet is installed. Note: Subfloor primers are recommended by some manufacturers for specific carpet installations to enhance adhesion.

—§9.2.5

Cushion Problems

Double-glue installations may fail when the surface of a cushion will not allow adhesive to bond to it. The cushion MUST be suitable for double-glued installation and the adhesive MUST be compatible with the cushion.

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.

Improper Rolling

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.

After sufficient adhesive application and open time, the carpet must be pressed into the adhesive and rolled with an appropriate roller. Rolling must be performed with the lightest roller that achieves full and complete coverage of the substrate and carpet backing, including penetration into the backing’s deepest recesses. Refer to manufacturer recommendations for roller weight. Roll the carpet in both directions, but do not roll excessively.

—§9.6

Rolling must be performed with the lightest roller that achieves proper transfer of the adhesive into the carpet back. Refer to manufacturer recommendation for roller weight. Roll the carpet in both directions, but do not over roll.

—§10.7

Investigating Bond Failure

Because numerous variables are involved, correctly diagnosing the cause of bond failure can be complex. In the illustrations below, pre-installation bond tests (Figures 9a and 9b) were conducted to assess the suitability of the slab to receive carpet. Fortunately, the tests identified a bonding problem before installation began. (Figure 10) Additional tests confirmed that an extremely strong bond could be achieved with additional floor preparation. (Figure 11)

References

CRI 104 - Standard For Installation Specification of Commercial Carpet

CRI 105 - Standard For Installation Of Residential Carpet

ASTM F-1869-98 – Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Calcium Chloride

ASTM F-710-98 – Standard Practice for Preparing Concrete to Receive Resilient Flooring

Last week I started sifting through a bunch of articles I wrote years ago for various industry publications. The topics are all over the map—too diverse to fit comfortably into one cohesive book (i.e., writing books is a lot of work), so I decided to dust them off and publish them here as my spare time allows. If there seems to be enough interest, I may even publish some new stuff that previously didn’t get past the “notes” phase.

What is Carpetology, anyway?

Carpetology is just a nonsense word, a descriptive catch-all for the loosely-related arts and sciences related to preventing, investigating and solving carpet problems. It’s a main course of engineering, chemistry, manufacturing, architecture, design, installation and maintenance, with side orders of psychology, intuition and curiosity.

The Carpetologist is someone who puts himself (or herself) in the middle of other people’s carpet problems and tries to sort things out. While they’re not necessarily textile scientists, cleaning wizards, or installation gurus, carpetologists are good at synthesizing the big picture—collating expertise from many unrelated disciplines to determine how some situation came to be and what, if anything, can be done about it.

Carpetology is the never-get-bored occupation where you learn more than you ever wanted to know about everything from concrete chemistry to Axminster looms to trip-and-fall biomechanics to sheep to construction law to pesticides to Georgia humidity in August. You get paid to crawl around on your hands and knees, tear things apart and use cool gadgets, frightening chemicals and big words.

Aside from the forensic fun, it’s sometimes tedious (I’ve literally been paid to watch glue dry), and people often get cranky when your findings don’t support their position. You’ll appreciate whole new dimensions of irrational consumer behavior and tragic business decisions, learn how committees work (or don’t), and understand the importance of wearing good socks.

To keep things interesting, I plan on posting articles on those technical subjects I know a little about, plus some useful how-to’s, rules of thumb, and maybe occasional rants if I get worked up about something. And if you like mysteries, I have a few truly bizarre case studies on deck to puzzle the daylights out of you.

Please let me know if you find these articles useful; if enough people do, I’ll keep ‘em coming. Feel free to post questions and comments, and I’ll do my best to read everything that comes in.

Here we go…