TPO and PVC Single-Ply
With TPO and PVC, seams are heat-welded, and the usual culprits are a weld that never fused, a foot-traffic puncture or an unpatched T-joint. The contractor probes the seams, cleans and preps the sheet, and welds in matching material. Weathered TPO sometimes will not weld cleanly, and that alone tells you something about remaining life.
Heat-welded seamsSeam probeT-joint patch
EPDM Rubber Roofs
EPDM is forgiving and long-lived, but its seams rely on tape or adhesive, and both let go with age and shrinkage. A repair usually means scrubbing with primer, applying cover tape or a cured patch, and re-securing perimeter flashing that has tented. Severe edge shrinkage usually calls for re-flashing the perimeter rather than more patches.
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
Water still standing 48 hours after rain is ponding, and most membrane makers do not like it. 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