Heat-Welded Sheet Membrane (PVC / TPO / WeldTec)

Factory-made single-ply sheet, hot-air welded into one continuous membrane

What it is

Single-ply thermoplastic sheet — PVC (polymer-modified vinyl, plasticised) or TPO (thermoplastic polyolefin) — manufactured to a controlled thickness, typically 1.2–2.0 mm, usually with a polyester reinforcement scrim or a fleece backing. The sheets are rolled out on site and joined by hot-air welding: the overlap is heated to its melting point and pressed, so the two sheets fuse into a single homogeneous material. The seam is not an adhesive joint — it is a weld, and it can be probe-tested and, where required, air-pressure tested along its length. Because the sheet arrives at full thickness from the factory, the finished membrane does not depend on wet-film build, weather during cure, or coats being applied evenly.

How we install it

Substrate first: the deck is prepared, dried and set out to the specified falls, and a vapour control layer plus insulation are installed where the build-up calls for it. The membrane is then secured by one of three methods, chosen by the roof, the wind-uplift calculation and the specification: mechanically fastened (fasteners and plates in the laps), fully adhered (bonded with adhesive, including cool-applied adhesive on fleeceback sheet where no penetration of the deck is allowed), or loose-laid over a geotextile separation layer and held down by ballast, pavers or soil. Field sheets are welded with a hot-air robot welder; corners, outlets, pipe penetrations and upstands are welded by hand with a hot-air gun and formed from preformed corners or from sheet cut on site. Terminations are made mechanically and sealed — into a chased reglet with a welded metal angle, or under a flashing or capping, using PVC-laminated metal that welds directly to the sheet. Every seam is then probed, and the roof is water-tested or, on tanks, filled and held. Where the manufacturer requires it, we install to their trained-installer requirements so the completed system qualifies for their system warranty.