How to Seal Carpet Seams
June 2, 2010
Do you seal your seams on all carpet that requires it? The majority of residential and commercial carpets that are constructed using a hot melt system require seam sealing by the manufacturers. In fact, there are only a handful that do not require sealing seams. Are you one of those installers that only seals Berbers on residential installations or only seals one side of the seam? Did you know that cut pile carpet requires seam sealing also? Actually, I’m not aware of any “stretch in” residential or commercial carpet that doesn’t require seam sealing of the seamed edges. Hot melt seams require that BOTH seam edges be sealed. Some of the reasons for not sealing seams I have heard are, that it takes too long to dry, it’s messy, costs too much, and the manufacturers should manufacture the carpet correctly so that installers don’t have to worry about sealing seams and edge ravel.
So if an installer does not seal seams, who is responsible if there is delamination or edge ravel along the seam, as in Photo 1? If the seam was not properly sealed when the manufacturer states that seams shall be sealed by the installer, then the installer is responsible. Now what happens if the seam edge ravels three years down the road? Is the installer responsible then? Yes! If the installer never properly sealed the seam when the manufacturer required it and the consumer maintained the carpet correctly, the installer will own the seam for the life of the installation. Why? Because the one- or two-year labor warranty applies only if the installation was done according to industry or manufacturer guidelines from the date of the installation. There may even be some manufacturer-related issues but if edge ravel or delamination started at the seam, they will inspect to determine if the installer used seam sealer at the time of installation. If you are not sealing your seams, you’re making a business decision stating that if the seam fails, you’re willing to pay the consequences. Does an installer really want this liability? I can’t imagine so.
The traditional method of sealing seams using hot melt tape is the use of a latex or acrylic seam sealer (Photo 2) generally applied with what is referred to as a speed tip (Photo 3).
The tip assists with the application of the seam sealer, which is applied between the primary and secondary backing (Photo 4). The types of seam sealer noted in the photo from left to right are: a universal acrylic, a hot melt acrylic, and a latex seam sealer.
The universal means that it can be applied to both a hot melt seam and a glue-down seam. The hot melt acrylic pictured in the middle is for hot melt only; this company manufacturers a different seam adhesive for glue-down applications. Acrylic seam sealers dry hard and fairly clear; the smell is similar to “white Elmer’s glue,” which is also an acrylic. Acrylic seam sealer can be cleaned while wet with a clean damp white cotton rag and a little soap if necessary. Latex has an ammonia smell, stays slightly tacky when cured and turns an amber color. If you get latex on the face fibers of the carpet, let it dry and then peel it off, DO NOT attempt to rub it off with a cloth, as it will be extremely difficult to remove. Use a hair dryer if you need to accelerate the drying of the latex prior to peeling off. Latex is used for hot melt only as surfactants or soaps used in cleaning the carpet, tend to break down the latex seam sealer over time in a commercial glue-down installation. Keep the two carpets being seamed, slightly separated before applying seam sealer so as not to contaminate the yarns. (Photo 5)
Notice the angle of the bottle, held from 45 to 60 degrees. Remember we are only applying seam sealer to the primary and secondary backing. There should be little to no seam sealer on the backing of the carpet, we are sealing the edges, not “buttering” the backing. Installers who have a difficult time with this tip should try to angle the bottle more and keep the carpet as flat as possible when applying the seam sealer. By lifting the carpet too much the installer will start to notice that the seam sealer will be applied more heavily on the backing rather than between primary and secondary backing. A small amount is only required followed by “rubbing” in the seam sealer along the edge and removing any excess. Seam sealer properly applied takes a very short time to dry. The blue tip has a slightly longer edge than the red tip but still requires the bottle to be placed at an angle for proper placement of seam sealer. There are some old school installers who prefer to use just the tip of the bottle rather than attaching one of the speed tips, I still use this method for woven carpet that is to be hand sewn. Woven carpet generally requires a bit more seam sealer along the edge and it doesn’t hurt to butter the back either when sewing (Photo 6). These types of seam sealer do not always fluoresce under a UV black light, so if an inspector only uses a black light to determine seam sealer, be wary.
My colleague Michael Hetts wrote an article several years ago utilizing a hot glue gun as a seam sealer in conjunction with a hot melt seam iron. Today there a couple of manufacturers that have designed hot melt glue gun seaming tips for hot melt seams. The industry now accepts hot melt techniques to seal seams. Utilizing these systems requires just a bit of practice to become proficient and the sealer cools very quickly so there is minimal chance of getting thermoplastic hot melt on the face fibers.
Photos 7 and 8 show a tip that the manufacturer recommends to push when applying the hot melt seam sealer.
Photos 9 and 10 show a tip that the manufacturer recommends be pulled when applying seam sealer.
Photo 11 is a tip that applies hot melt seam sealer to both edges at the same time; this type of tip is recommended for the Kool Glide radio wave seaming tool, and is also recommended to be pulled while applying hot melt seam sealer.
The idea behind using hot melt to seal the seams is that when the seam iron is passed through, it will reactivate the hot melt that was used to seal the edges and bond the two edges together. Some installers try not to turn the heat up too high on their irons to minimize any backing distortion. If the hot melt does not heat up and reactivate to bond the two edges, does this mean that the seam is not properly sealed? No, the seam is still sealed. There may be a potential for seam peaking as the two edges are not bonded but it is still an acceptable sealed seam. If the installer is noticing that his or her seams are not bonding when using the hot melt seam sealer system, try a couple of techniques. First, try to use a lower melting temperature glue stick; make sure you are constructing your seams over a hard surface such as a 1/4”x 10”x 4’ piece of underlayment with a notch at one end so that the seam tape can slide through as you move the board; use a seam roller and seam weight. If this doesn’t work, you may want to make small adjustments to increase the heat from the seam iron; you just want it hot enough to re-melt the hot melt seam sealer and not distort the backing.
If you have never used the hot melt technique, I recommend purchasing a small black light. Many of the hot melt glue sticks sold at the flooring supply distributors will fluoresce under a black light. This will enable you to see the hot melt coverage along the seam edge and determine if you used too little or too much (Photo 12). Seam sealing may seem to some a waste of time or a necessary evil but if it keeps my money in my pocket rather than someone else’s, it’s worth the time and effort to invest to do it right and seal the deal!