Heat-Welded Seams Open in a Cold Hospital Corridor
An 1,200 sq ft hospital corridor is receiving homogeneous vinyl sheet with heat-welded seams. The building heating system is not commissioned, and the corridor stays at 52 degrees F at night and 58 degrees F during work. The adhesive label requires 65 to 85 degrees F for 48 hours before, during, and after installation. The crew unrolls the sheet, lets it relax for 2 hours, and installs it with a 1/16-in. notched trowel. They roll the floor immediately with a 100-lb roller. The next morning they weld the seams with a hand welder, trim the rod while still warm, and turn the corridor over to hospital traffic that afternoon. Within 10 days, seams are peeking and weld rods are cracking; the sheet has pulled 1/8 in. at two doorways. The manufacturer's instructions are on site but not read.
1. Identify the probable causes of the seam and weld failures. Explain how the symptoms support your diagnosis.
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Temperature is the primary cause. At 52 to 58 degrees F, the adhesive is outside its 65 to 85 degree F range, so it does not develop tack or cure properly; the vinyl is also stiff and contracted. Two hours of relaxation is not acclimation. Welding the next morning may have trapped solvent or moisture, and trimming the rod while warm can pull the seam open as it cools. Turning the corridor over the same afternoon puts traffic on uncured adhesive. The 1/8-in. pull at doorways is consistent with sheet contraction and poor bond, not a defective sheet.
2. Outline the corrective work and the sequence needed before the corridor can be released again.
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Stop traffic and cut out the failed seams and any loose sheet back to sound adhesion. Bring the corridor to 65 to 85 degrees F for at least 48 hours before, during, and after reinstallation. Reinstall with the specified trowel, roll in both directions, and allow the adhesive to cure before welding. Weld, let the rod cool, trim in two passes, and keep traffic off until the adhesive and weld are fully cured. Replace sheet if it has taken a permanent set or is contaminated. Re-test a mockup seam before doing the full corridor.
3. What records and jobsite controls should prevent a repeat on the next phase?
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Use a daily temperature log, a written acclimation period, and a pre-installation meeting with the GC. Require HVAC to be operating or provide temporary heat. Record product lot, trowel size, open time, roller weight, weld time, and cure time. Photograph the mockup and retain manufacturer instructions on site. Document the delay as a schedule impact if temporary heat is not provided.