In this second article covering pattern matching carpet, we’re going to cover how to determine pattern tolerances prior to installing and hopefully saving both time and money for the installer. I was recently at a CFI carpet installation certification in Salt Lake City, Utah, at a retailers facility, R.C. Willey, where we had the opportunity to work with installers covering patterns, constructing seams and stretch-in/glue down techniques of patterned carpet (Photo 1).

So, let’s review again what tolerances installers need to understand prior to installing patterned carpet: Bow, Skew, Pattern Elongation, and Edge Deviation/ Trueness of Edge are the four key things installers need to determine. I tell installers, depending on what the carpet tolerances are after checking will determine if we have a regular day of installing, or a very long day or days to properly align patterns.

What do we need to determine tolerances?

  • Tape measure
  • String line, preferably a bright colored line
  • Straight edge
  • Square
  • Blue tape
  • Laser that has right angle lines (option to replace straight edge and square)

Prior to documenting pattern tolerances, the retailer and the installer must understand what the tolerances are and what the installation guidelines of each manufacturer state. Unfortunately, there are no specific industry standards for these tolerances so manufacturers of carpet can have varying tolerances, and if the retailer or installer is not aware of what each manufacturer’s specific tolerances are, then one can get into trouble by assuming. If you look at the installation guidelines of several manufacturers, you’ll see that bow is approximately 1” in 12’ on average, skew is 1 1/2” to 2”, pattern elongation is 3/4”- 1.25”, and edge deviation/trueness is 1/2”- 1 1/2”—but once again, make sure to find out from the manufacturer what the specific tolerances are.

Since many patterns are difficult to locate, if you have a couple of installers trying to determine tolerances then placing blue tape on the repeats or where you want to align patterns is a quick, easy way to keep your reference points visually in place for all to see, as demonstrated in Photo 2 featuring installer Juan Servantes.

Set match. Think of a set pattern as having a square; now put a penny on each corner. If you were to line these squares with the pennies in each of the four corners this would be considered a set match (Photo 3).

Drop match. If you take the same square and place a penny in the center of the square, you will have a drop match. By having the penny in the center of the group, the pattern can now drop half of the repeat of the square, thus creating the drop match (Photo 4).

Bow: Deviation from a straight line across the breadth (width) of the carpet. To check for bow, determine the same pattern at each side of the carpet and then stretch a string line across to the two points. Determine where the difference of pattern deviation is and measure the distance from the string line—this is typically at the center of the carpet, but there can also be deviation toward the edges so measure and document what and where deviation is (Photo 5). We found that the bow on this product measured 3/8” at the center.

Skew and squareness of the pattern. Skew and pattern elongation are the two issues that get installers in the most trouble. Many jobs end up having to be paid by the installer or retailer for skew and pattern elongation issues that may have been out of tolerance to begin with, but once the installer installs the product they have accepted the carpet for what it is.

Start by using a straightedge to align at least two patterns along the edge of the carpet; once the straightedge is running straight along the patterns, align a framing square next to the straight edge. Once you have established which pattern you are going to align to, then stretch the string line taut across the breadth of the carpet and follow the square (not the pattern). If you need another straightedge to give a longer edge than just the framing square, you can just line it up to the framing square and use the string line along the straight edge.

Once the string line is in line with the straight edge, if there is any deviation from the other side that the straight edge was matched to, measure the difference. This is what your skew will be. On the piece we measured, I asked the group of installers if they thought the carpet looked out of square. They all thought it looked fine. Once we measured and documented the difference they were surprised to see we were 1 1/2” out of skew (Photos 6 and 7).

Pattern Elongation: How much the patterns vary over a measured length or width, then varies from one breadth of carpet to another at the seams. The next step is determining if the pattern repeats on both sides are the same. If they’re not, this is where installers need to manipulate the carpet to match at the seams.

We took blue tape to mark which pattern we wanted to use, then we counted out 18 patterns on one side of the breadth. The measurement of the 18 patterns equaled out to 114.25”. We then measured 18 repeats on the other side of the breadth and came up with 113.5”. There was pattern elongation of one side of 3/4” (Photos 8 to 10).

Edge deviation: How much the edge deviates along the edge. Using the string down the length, along the edge of the carpet, we found there was 1/4” in 12’ edge deviation (Photo 11).

So our carpet had 3/8” of bow, 1 1/2” of skew, 3/4” of pattern elongation, and 1/4” of edge deviation/trueness. What does this mean? It means we’ll have a longer day. We need to adjust the bow until it’s straight when looking across the breadth. This won’t be too hard to accomplish due to the small variance.

The skew, depending on the layout, could be a concern. If there were three breadths of carpet installed side by side, and if we didn’t do anything to straighten out the pattern, this is what would happen. From the first breadth being out 1 1/2”, the next breadth would be out 3”, and the third breadth would be out 4 1/2” at the end walls. The pattern would keep running off whatever the amount of skew is with every adjoining breadth. In a room with multiple breadths this is visually very unsightly and is usually not acceptable by the end user.

The pattern elongation of 3/4” will also be a challenge, but we can make it easier to work with. When constructing the seams, start in the center and work away from there. This will take that 3/4” of pattern elongation we had and cut it in half. It’s much easier to manipulate about 3/8” versus fighting the 3/4” along the whole length.

The edge deviation/trueness fortunately is not a factor; we can manipulate any slight gaps or overlaps with a knee kicker. (Seams were sealed prior to maneuvering the carpet and constructing seams.)

The group used multiple tools to construct a seam on a patterned piece of carpet that had 3/4” pattern elongation (Photo 12):

  • Dead man (a board with tack strip on the bottom to use as a portable wall)
  • Powerstretcher
  • Koolglide seaming tool, which uses radio weave/induction technology
  • Seamer Down Now, a seam cooling device that draws air up through the carpet, cooling the seam much quicker without compromising the integrity of the seam

To speed up production since we already know it’s going to be a longer day, this is what you can do with these tools. Use the dead man, Koolglide and the Seamer Down Now to “spot bond.” Align the patterns from the center of the seam, as the installer is doing in the photo with the dead man and powerstretcher.

Activate the Koolglide seaming tool, and once the light goes off on the Koolglide, place the Seamer Down Now over that area, turn it on, wait 30 seconds, release the powerstretcher pressure and move up a few feet or whatever is necessary to align the seam again.

Repeat the process of “spot bonding” until you reach the end and then repeat on the other half of the seam. To speed up the process, if you have another Koolglide available, another installer can be following right behind and engaging the Koolglide along the entire length and go right over the areas you “spot bonded” as the seam tape can be reactivated. Make sure to keep the carpet nap sweep going in its natural direction when seaming against the nap. Another nice thing about this procedure is no stay nails are required!

When installing a glue direct installation, many installers use what we refer to as “stay nails.” These are used on wood or concrete and depending on which type of subfloor, the appropriate nail is used. One way of minimizing the use of stay nails is to use a piece of tack strip—Tri-tack or architectural strip work great for this type of use.

Take the tack strip, place it upside down with pins into the carpet pointing away from your stretch. Once you align the pattern or bow, place nails through the tack strip to hold the strip in place. You’ll find that you can use less nails and the use of the tackstrip will keep the alignment much straighter than the use of nails alone (Photo 13).

As I stated in part one of this series last month, patterned carpets require more skill and time to achieve a professional, industry-accepted installation. The good news? That should equate to more money for the qualified installer.