Namba's World

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Constructing straight seams is an everyday occurrence for most installers, but what about those installations where borders and miters are involved?

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How do we finish off the mitered corners where we have three pieces of carpet coming together and one seam is running off on an angle?

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I thought that this would be a topic needing some attention, as I have been involved with several corrections of mitered corners that have been a result of installation, and if this article can help even one installer I feel that it will accomplish its purpose of helping to prevent a call back or replacement.

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Photos 1 and 2 are examples of a border job gone bad. This particular carpet was a Wilton weave, which should have never been installed with seam tape in the first place, in my own opinion, but the illustration of the seam tapes make a great example of what not to do on carpet that uses a hot melt seam tape.

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Photos 3 and 4 show what can happen using seam tape on this particular carpet: the face fibers of the border and field are fraying. Photo 5 shows seam tape that is misaligned. This installation was in a residential home in a family room; the retail cost of the flooring and labor was approximately $16,000 for a 14-foot by 18-foot room.

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The interior designer also specified that the installation have binding visible, around the entire perimeter and stretch in over a cushion, a challenge for even the most experienced installer.

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Notice in Photo 1 the irregularities of the seam tape in the straight portion of the seams.

Photo 9
The seam was not constructed on a hard surface, the installer did not use a seam roller, and there were several stop and go marks from the seaming iron. Photo 2 shows four seam tapes coming together at one point; notice that each tape is overlapping, creating four layers of seam tape. Also notice the distortion of each tape at the intersecting point.

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Seaming tapes have silicone applied to the backing to keep the seaming tape from sticking to the cushion. The same applies when seam tape is applied over another seam tape.

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Although there are four tapes at this intersection, each tape overlapping each other at the seam edge creates a very weak seam.

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Sanding or scraping the paper backing does not always work and still creates two or more layers of seam tape, remember, we are trying to maintain as flat a surface as possible so that we will have minimal seam profiling.

To ensure a proper seam, seal all seams prior to seaming, as shown in Photo 6. Construct border seams up to miters, as shown in Photo 7, which shows a common method of constructing hot melt seams up to the mitered corner. Mark the bisecting points (Photo 7) Cut the first angle (Photo 8). Next, as shown in Photo 9, overlap the angle cut over the uncut border and mark by carefully cutting a small slit at each end of the miter; then cut the second angle (Photo 10).

Photo 11 shows a method that I see quite often: the seam tape that is placed under the mitered corner is cut to fit to the two seam tapes.

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The circle is the intersecting point of all three carpets. When viewing this photo, do you see a problem with this method? Although the area around the intersecting point has seam tape covering the entire area, there is no structural integrity of the seam at the intersecting point. Have you ever noticed a slight gap at the intersecting points after you have stretched in a border installation?

Here is a method that I have found that works well for me. As shown in Photo 12, cut a piece of seam tape to fit the mitered corner. Cut the portion of paper that does not have any thermoplastic. Trace around the seam tape and transfer the marks on to the other two seam tapes. Gently score the two seam tapes along the trace line and remove the seam tape. If you have difficulty removing the tape, clean the bottom of your iron on a scrap piece of carpet and slightly heat the tape from the back and remove. Use one end of the iron to heat the two areas to be removed. Do not place the entire iron on the backing as it may distort the backing and this will be visible from the face side of the carpet.

You must remove the paper on the edges or else you will have a gap on each side of the seam that will create a weak point. The circle is where the intersecting points are located; this is a structurally sound seam with no overlap of seam tape (Photo 13). Compare this photo with Photos 1 and 2, and you should see a big difference.

We were able to save the Wilton job, but removing all of the seam tape was required. Hand sewing the fills and borders was required for a proper installation.