Seam Failure Repair in Brockton, MA
A seam that splits in January was usually weak in July. Cold only exposes it. Nobody sees the lap that never quite bonded, the weld that skipped a stretch, or the splice laid over dust, until the membrane shrinks on a bitter night and pulls the joint apart. Seam failure on a commercial roof in Brockton, MA is a story about a hidden defect meeting repeated freeze and thaw. The fix is to find the defect, not to run caulk along the line.
How seams come apart
Three things open a seam. The original bond was poor, from a cold weld, a dirty surface, or a splice made in damp weather. The roof moves at that line, usually over a deck joint or an insulation board edge. Or the seam has spent years under standing water, which breaks down the bond slowly from underneath.
Each cause leaves a clue. A seam that opens in a straight line over a deck joint has been flexing there. A seam with a clean, shiny separation never welded at all. A seam with brown staining and soft edges has been sitting wet. We read the opening before we repair it, because the same weld on the same spot will fail again if the cause is movement.
What the cold does to a lap
Membrane shrinks as it cools. On a roof that sees a record low of minus 19 degrees Fahrenheit and cold snaps through the winter, the sheet pulls on every seam it has. A well-made weld handles it. A marginal one lets go at its weakest point, often a T-joint where three layers meet.
Wind adds fatigue. Brockton averages 14.3 mph, so a loose edge of membrane flutters constantly. That flutter works a partly open seam wider, and the gap collects water that freezes. By spring a pencil-width gap can run for yards, and a roof with wind damage often has seams that began opening well before the storm.
Probe every seam, not the visible one
The open seam you can see is a sample. The ones around it matter more. We run a probe along every lap in the repair area and well beyond it, testing for lifted edges, soft bonds and pinholes. On single-ply roofs the probe finds welds that look fine but pull apart with a light push.
The same goes for the repair itself. We test each new weld before moving on, and look for the thin line of melted membrane, called a bleed-out, along a good heat weld. A weld without it is suspect. For a roof that has seen several seasons of seam problems, a sweep of the whole roof costs far less than coming back for each opening in turn. A planned maintenance visit catches these before winter.
Look under the seam at the fasteners
On mechanically attached systems, the seam sits right beside a row of fastener plates. If a plate backs out or the deck beneath it loosens, it lifts the sheet at the edge of the weld and pries it open from below. Welding over that situation gives a clean-looking seam that peels again in the next windy week.
So we check the plates on both sides of an opened lap. Loose ones get reset or replaced, and the area is probed for moisture, since a leak at a plate wets the deck under it. Where the deck itself is rusted, fastener withdrawal is the real problem, and the fix is a deck repair before any membrane goes back. Fixing the weld without the fastener is the repair that fails by spring.
Repair seams by membrane type
On TPO and PVC, we clean both surfaces, heat weld a cover strip over the opened lap, and finish the edge so water cannot get under it. On EPDM, seams are bonded with splice adhesive or tape, so repair means cleaning back to fresh rubber, priming, and laying new tape with firm pressure along the length.
Modified bitumen and built-up roofs have laps that are torched or mopped. A lifted lap gets reheated or recut, and a cap sheet seam may need a new strip of membrane set in compatible cement. Aged membrane complicates all of this. Old TPO or PVC can be too brittle to weld cleanly, and then a liquid-applied detail over a mechanical termination may be the safer choice.
Long runs on big buildings
The wider the roof, the more seam length it carries, and a low-slope roof is mostly seam and a few penetrations. A 109,000-square-foot Parker Drive building in the Avon Industrial Park houses distribution operations, and the park holds 127 firms around Route 24. Over in Taunton, the Myles Standish Industrial Park spreads across more than 800 acres and mixes manufacturing, offices, high-tech firms and distribution centers. On a large low-slope roof, a seam survey is a mapped job, with every lap logged by location.
On big roofs we set a repair order. Active leak zones first, then the long runs near drains where water collects, then edges and corners. A seam beside ponded water is the most urgent, because it is under load all the time.
When repair is not enough
A few opened seams are a repair. Seams opening everywhere across the field, with a brittle sheet that cracks when bent, mean the membrane has reached the end of its life. At that point, chasing individual laps wastes money, and the owner should price repair work against a recover or replacement. We say that plainly, with core cuts and probe results laid out so the decision rests on the roof.
Commercial Roofing Questions
Why did my seam open when the roof is fairly new?
A new roof can fail at a seam that was welded cold, contaminated, or made in poor weather. Installers test welds for exactly that reason. If a young roof shows open laps, probe all of them, and bring in the installer's records before accepting a patch as the whole answer.
Is a cover strip as good as the original weld?
A properly welded cover strip over a clean lap holds as well as the original bond. It adds membrane over the opening and carries stress across the gap. The weak link is how well the strip is welded at its own edges, so we test those.
Can seams be sealed with a coating instead?
Coatings can protect a sound seam and slow wear. They do not replace a bond. If the lap has opened, coating over it hides the gap and water still gets in. The joint needs a weld or splice first.
What temperature do you need for seam repair?
Welds and adhesives need dry, clean surfaces and workable temperatures. In a cold snap we use tarps or temporary seals to keep water out, then schedule the permanent seam repair for a window when materials cure properly.
How many seams should I expect to fix?
That depends on what the probe finds, and we count after testing rather than guessing from the ground. We give the owner a list showing each opened lap, each suspect lap, and the repair for both, so the scope is visible before work starts.
Do seam repairs show up on an inspection report?
They should. We log the location, the cause, and the method for every repaired lap, with photos before and after. That record helps with a warranty file, with a claim, and with planning the next round of work on the same roof.