How a TPO Roof Is Installed

Three attachment methods

• Mechanically fastened — plates and screws through the membrane at the seams. Lowest cost, fastest, and the membrane flutters visibly in wind
• Fully adhered — bonded across the whole surface with adhesive. Better wind performance, flatter appearance, more labour
• Induction welded — plates fastened to the deck, then the membrane welded to the plates magnetically. No penetrations through the finished membrane

Seams are the whole game

TPO seams are hot-air welded, and the weld depends on temperature, pressure and speed — all of which change with ambient conditions through the day. A crew that does not adjust gets cold welds that pass visual inspection and fail in year three.

Proper practice is a test weld at the start of each shift and when conditions change, plus probing finished seams with a hook to find any section that did not fuse.

Details, in order of how often they fail

• Curb flashings at HVAC units
• Pipe boots and their sealant, which ages far faster than membrane
• Drain sumps and clamping rings
• Inside and outside corners, which are prefabricated or hand-welded
• Parapet terminations and counterflashing
• Walk pads, whose absence turns service traffic into punctures

What to require in a bid

• Membrane thickness in mils, stated
• Attachment method, stated
• Insulation type and R-value, stated
• Warranty type — material only, or a manufacturer system warranty including labour — and its term
• Daily test welds and seam probing included
• Walk pads at every roof access point and around serviceable equipment

Common questions