Seam Failure Repair in Tuscaloosa, AL

On a heat-welded single-ply roof, the superintendent walks the lap lines with a seam probe in hand, because a seam that looks closed from standing height can lift under a probe tip and show a gap that runs for yards. The probe is a thin, rounded steel tool, and the test is simple: if it slides under the edge of the lap, the weld or the adhesive has failed. Seam failure repair in Tuscaloosa, AL starts with that test along every lap in the affected sections, records each open or split seam on the roof plan and then finds out why it opened, since a seam repaired without a cause usually opens again.

Probing Seams: What Open Looks Like

An open seam has three common forms. A fishmouth is a small lifted edge on the top sheet that curls up and catches dirt. A split is a cut along the lap where the membrane has pulled in two directions. A cold weld is a seam that never fused, which shows as a smooth, shiny edge that peels apart without tearing the sheet. Each tells us something about when the problem began.

We probe every lap within a section and flag the ones that open, then work outward until the seams are tight. A cluster of failures along one wall points to movement or shrinkage at that wall, while failures scattered across a field suggest a workmanship issue from the original installation. The map of probe results is the foundation of the scope, and it tells the asset manager how many seams will be touched and how much of the roof is in question.

We also look at what sits on the seam. Dirt, standing water, a rooftop unit's condensate line or a worn walk route across a lap each add stress, and the repair includes a correction for any of them: a diverter for the drip, a pad for the foot traffic or a drain adjustment for the pond.

Heat-Welded Seams and Cold Welds

TPO and PVC are joined by hot air, which fuses the two sheets into one. A good weld shows a continuous bead, a slight squeeze-out and a seam that cannot be peeled. A bad weld was too cool, too fast or made over dirt, and over time it opens as the sheet moves.

The repair is a new weld. We clean the area, grind or scrape any contamination, and run a hot-air welder with a roller over a cover strip that extends beyond the damaged length in both directions. The weld is probed after cooling and tested for a pull-apart, with a small sample cut and peeled to see whether the sheets tore before the weld let go. A weld that peels cleanly is redone; a weld that tears the sheet is sound. If the existing sheet has aged so much that it will no longer fuse, we say so and recommend a different repair, since a weld on an old membrane often fails at the edge of the new work. On a large building, such as the 700,000 square foot facility an automotive supplier planned in the Cedar Cove Technology Park, a single-ply roof would mean long seam runs, and a clean probe record becomes especially important.

Adhered Seams, Tape and Modified Bitumen Laps

EPDM sheets are joined with seam tape or splice adhesive, and these fail when the surface was dirty, the adhesive was applied in damp weather or the tape was stressed by movement. The repair is a new primed splice or a cover strip of tape, pressed with a roller from the center outward.

Modified bitumen laps are heat-fused or set in cold adhesive. A lap that has opened shows a dark gap and loose granules at the edge. We clean it, re-heat or re-adhere it and add a cover strip when the lap is badly worn. Where the surface is granulated cap sheet, we embed the granules into the hot asphalt at the edge so that the repair resists weather. Each repair is numbered on the plan, and its material and method are recorded so that the next inspector finds it and knows what it is.

Fastener Back-Out and Seam Stress

In a mechanically attached system, a row of fasteners runs under or beside the seam, and when a fastener backs out the plate lifts the sheet, wears the membrane and stresses the weld. The result is a seam that opens above a fastener row and a line of small bumps that can be felt with a hand.

We find the loose fasteners, pull a sample to check the deck's grip and reset or replace them. If the deck is corroded or the fastener has lost its bite, a row is added next to the old one. A seam repaired over a loose fastener is a repair that returns, which is why the fastener check is part of every seam scope and why the same crew that welds also pulls the test.

Heat, Cycling and the Tuscaloosa Summer

The recorded extremes run from 107 F down to minus 1 F, and the sheet on a roof moves through a wide part of that range every year. A dark membrane in summer sun is hotter than the air, and it cools quickly after a thunderstorm. Each cycle pulls on seams, particularly at the edges, corners and flashing, where the sheet is restrained and cannot move freely.

Seams at walls and curbs are the first to show it, and a failure at a termination is also a flashing failure. Standing water adds another stress, and a seam in a pond opens sooner, which is why a ponding water repair often accompanies a seam scope. Where a roof has many failures at once, the membrane may be near the end of its life, and we compare repair with a recover before the owner spends more.

What to Carry on the Books

The deliverable is a probe map, a repair list and a decision. The probe map shows every open seam by section. The repair list says what will be welded, taped or replaced, with a cost for each section. The decision compares spending to repair with the remaining life of the roof, so the asset manager can budget accordingly and decide whether a section should be repaired now, watched through the next storm season or scheduled for replacement. For owners with sites such as the Tuscaloosa Airport Industrial Park, the same format can be repeated for each roof so the results are comparable.

Commercial Roofing Questions

How is an open seam found?

With a seam probe along every lap. If the tip slides under the edge, the weld or adhesive has failed. We mark each one on the roof plan.

Why does a seam open months after it was installed?

Common causes are a cold weld, dirt in the lap, shrinkage at a wall or a loose fastener below. We find the cause before repairing.

Can a failed seam be caulked?

Not for long. Caulk sits on top of an open lap and cracks as the sheet moves. A new weld, splice or cover strip restores the joint.

When is a seam failure a sign the roof is finished?

When failures are widespread, the sheet will no longer fuse and moisture is in the insulation. We compare repair costs with a recover or replacement.

Do seam repairs need a core cut?

Not always. Where water has entered, we scan and cut a core to check the insulation, because a dry seam repair over wet board will fail.

How are repairs recorded?

A plan number, a dated photograph and a method note go with every repair, so a later inspector can probe the same spot and compare.