Waves That Return Six Weeks After a Re-Stretch
A facilities manager at a six-chair dental clinic reports that a 14-month-old carpet "keeps waving." The goods are a 32-ounce, 1/10-gauge solution-dyed nylon cut pile over 3/8-inch rebond pad on plywood, installed stretch-in against 2-inch tackless strip. The waves run across the 24-foot room width. A previous crew re-stretched only the length about three months ago, and the waves returned within six weeks. A 6-inch seam separation has opened at the entry where the carpet meets ceramic tile. In front of the sterilization room, a 4-by-6-foot area feels spongy, and a bubble moves ahead of the foot when it is walked on. The clinic sets HVAC back to 84 degrees F on weekends, and logged relative humidity swings between 28% and 70%. A tuft pulled at the exposed entry edge comes away with a tuft-sized piece of backing attached. The manager wants to know whether to re-stretch again, replace the carpet, or call the manufacturer.
1. What inspection sequence would you follow before recommending any remedy, and which test separates a stretch failure from a backing failure? Explain what each result means.
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Work from the general to the specific. Do not quote a fix on the first visit.
- Records and interview. Installation date, installer, and whether a power stretcher or only a knee kicker was used. The fact that the previous repair was lengthwise only is already a red flag: a carpet needs stretching in both directions.
- Environment. Get a week of RH and temperature logs, and moisture-meter the plywood at the entry, at the sterilization-room boundary, and at a known-dry control area. A high reading beside the spongy area moves the diagnosis toward moisture-related failure rather than lost stretch.
- Tackless and edges. Lift the carpet off the strip at several points. Well-engaged tacks plus a slack field means the stretch was lost, not the attachment.
- Seam and edge condition. Photograph the 6-inch opening. Check whether the backing was trimmed or heat-damaged at the seam, because that changes how you read a pick test taken there.
- Pick test. Pull a tuft. A small tuft plug with a little primary backing is normal tuft bind. A coin-sized release in which the secondary separates from the primary is delamination. Repeat in at least five locations, not only at the seam.
- Slack measurement. Push the carpet toward the wall at several points. An inch or more of slack within a few feet of an edge confirms lost stretch.
Only after steps 5 and 6 do you choose between re-stretch and a warranty claim.
2. The pick test at the entry releases yarn with backing attached; the same test two feet from the back wall releases only face yarn and the backing stays intact. The RH logs show 28-70% weekly swings. What is your diagnosis, and how much weight should the humidity data carry?
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The two results point in different directions, and the location explains why.
A release at the entry seam that carries backing is most often a seam-edge artifact: the backing was trimmed during seaming, seam sealer wicked into the tuft bundle, or the edge was crushed by the previous repair. It is a localized defect, not proof of field delamination. The clean tuft bind two feet from the back wall shows the latex precoat is doing its job in the field.
The humidity swings are real but should not be treated as the primary cause. A conditioned building on plywood is not a wet environment. What the swings do explain is relaxation: a carpet stretched under dry weekend conditions and then humidified will give back some of its stretch, and a carpet that was only knee-kicked or stretched in one direction has no reserve to give back. The returning waves after a lengthwise-only repair fit lost stretch far better than they fit a manufacturing defect.
Conclusion: field backing is serviceable; the entry tuft release is an edge condition to be cut out and re-seamed. The primary failure is inadequate stretch, aggravated by repeated weekend setbacks. Confirm with a slack measurement before you commit, and note in the file that the humidity history will keep working against any repair that does not include a proper two-direction power stretch.
3. State your recommendation and what you would put in writing, including how you would handle the spongy 4-by-6 area.
Read the worked answer
Recommendation, in three parts:
- Spongy area first. Lift a 12-inch inspection flap. If the primary has separated from the secondary, that section cannot be re-stretched into a flat field. Offer either a full-width section replacement bounded by natural breaks (a doorway or the sterilization-room wall), or a warranty claim if the delamination is field-wide rather than local. Do not re-stretch over a delaminated field; it will ripple again and you will own the callback.
- Re-stretch properly. Acclimatize the carpet 24-48 hours at normal operating conditions, replace any tackless that is crushed or set with pad over it, then power stretch both directions with a proper tail block and hold each gain on the strip. Elongation should follow the manufacturer's written specification, typically in the range of 1% to 1.5%.
- Re-seam the entry with a new clean edge and seam sealer, and re-trim rather than patch the old opening.
In writing: photographs of each test location, moisture readings, the RH log, a statement that the prior repair was lengthwise only, and the pick-test results. Add an advisory that maintaining 30-50% RH and avoiding deep weekend setbacks will extend the life of the repair, and that repeated cycling will eventually relax any stretch-in installation. Give a written caveat that the spongy area is excluded from the re-stretch price until the flap inspection is complete.