TPO and PVC Single-Ply
Thermoplastic membranes are joined with heat, not glue, so most leaks trace to a cold weld, a puncture or a T-joint that never got a patch. The contractor probes the seams, cleans and preps the sheet, and welds in matching material. Older TPO that has gone chalky may refuse to take a weld, which is a real sign the roof is near the end.
Heat-welded seamsSeam probeT-joint patch
EPDM Rubber Roofs
Black rubber roofs last, but seam tape and adhesive do not last forever, and shrinkage pulls the sheet away from walls and curbs. A repair usually means scrubbing with primer, applying cover tape or a cured patch, and re-securing perimeter flashing that has tented. If the membrane has shrunk hard at the edges, expect the contractor to talk about a perimeter re-flash.
Seam tapePrimerPerimeter tenting
Modified Bitumen and Built-Up
Mod-bit and built-up roofs are multi-ply, so they tolerate abuse, but blisters, alligatored surfacing and split base flashing are common on older ones. Repairs can be torch-applied, cold-applied or mopped in hot asphalt, depending on the deck, the occupancy and the fire watch rules on site. Gravel-surfaced roofs may need the aggregate scraped back first.
Torch-downCap sheetBlister repair
Drains, Scuppers and Ponding
If water sits more than two days after a storm, that is ponding, and it shortens membrane life and loads the deck. Contractors clear strainers and leaders, reset drain clamping rings, add crickets behind curbs and use tapered polyiso to rework low spots. A deck that sags between joists is past a roofing fix and may need an engineer.
Tapered polyisoCricketsClamping ring
Parapets, Copings and RTU Curbs
Plenty of so-called roof leaks start at the edges and penetrations, not in the open membrane. Loose coping caps, open parapet joints, failed counterflashing and rooftop unit curbs with short base flashing let water in behind the sheet. The fix is often re-flashing the wall, adding coping cleats and sealant, or raising curb flashing to the height the manufacturer calls for.
Coping capCounterflashingRTU curb
Restoration Coatings and Moisture Surveys
A fluid-applied silicone or acrylic system can extend a tired but dry roof without a tear-off. That is the catch: coating over wet insulation just seals the problem in. Expect an infrared scan at dusk, a capacitance meter grid or core cuts before anyone recommends a coating.
Silicone coatingInfrared surveyCore cuts