TPO membrane: a white sheet on a large roof

The roofs where it belongs

TPO performs best on a large, open surface: warehouse, light industrial building, big-box store. Where people walk a lot, it needs extra protection.

TPO is one of the commercial roofing membranes known as single-ply. Its lifespan is in the range of 20 to 30 years, according to manufacturers and depending on the quality of installation.

From roll to weld

The sheet is delivered in wide rolls. A scrim embedded in the material gives it tear resistance. It is commonly attached in two ways.

• With screws and plates. The membrane is fastened to the deck along the edge of each sheet, and the next sheet covers the fasteners.
• Fully adhered. The whole surface is glued to a cover board.

The sheets overlap at their edges and hot air melts the overlap. Once cooled, the seam is one with both sheets.

What works in its favour

• Its whiteness. It reflects the sun's radiation. The manufacturer's data sheet gives the solar reflectance index.
• Its light weight. A warehouse or plant steel deck handles it well.
• Its speed. On a clear surface, wide rolls go down fast.
• No flame. Screwed down, it gives off few odours, an advantage in an occupied building. Glued, it can smell strongly because of the adhesive.

What can go wrong

• Punctures. With a single ply, a forgotten screw, a dropped tool or a panel dragged across the roof can hole the sheet.
• The operator's hand. A good weld requires the right temperature, the right speed and clean surfaces. A failed weld looks fine and lets go later. The roofer must run a probe along the seams throughout the installation.
• Cluttered roofs. Every pipe and every equipment corner gets a piece welded by hand, and the time gained elsewhere is lost there.
• Grease. What a restaurant hood exhausts can damage the membrane. The manufacturer will say what protection to plan.

TPO and Laval's Code de l'urbanisme

TPO membrane is on the list of permitted roof coverings in section 379 of the Code de l'urbanisme (Laval's urban planning code). On a flat roof, section 380 also requires a green roof, a white material or a solar reflectance index of at least 78, attested by the manufacturer's specifications or by a professional's specification. The Code does not address the case of an existing roof redone identically. Keep the membrane's data sheet with the quote.

What to have written into the quote

1. Roofs of the same size the roofer has already done with this system.
2. The thickness of the membrane.
3. The method used to check the welds.
4. Protection for walkways and around mechanical units.

Frequently asked questions