A dry, clean and firm base
Nothing goes down before the layers underneath are ready. From one job to the next, we remove the old covering, replace deck planks damaged by water, and install a vapour barrier, insulation and a cover board.
An elastomeric membrane ages badly on a damp base or one that gives way underfoot. All the care put into the rest changes nothing.
Torch or film: two ways to bond
We choose the method before unrolling the first sheet.
With a torch. This is the traditional way. The torch melts the bitumen and gives a clean weld, even in cool weather. The downside is obvious: an open flame works next to dry wood, old insulation and neighbouring walls. The crew protects fragile areas, keeps fire extinguishers at hand and stays to watch the roof once the torch is off.
Self-adhesive. The underside of the sheet is coated with an adhesive covered by a release film. The film is peeled off at the moment of installation. The method needs no flame. In return, the adhesive needs a very clean base and a mild enough temperature to set.
Have the method stated in the quote. If it is the torch, ask the contractor whether their insurance covers that work.
The first ply
We unroll the base ply in parallel strips. Installation starts from the lowest point of the roof. Each overlap is then oriented in the direction the water flows. A strip overlaps the previous one by a few centimetres.
The product and the substrate dictate the attachment: welding, adhesive or fasteners.
The second ply
The finish ply, the one carrying the granules, comes next. The seams of the finish ply are offset from those of the base ply. Two joints are never stacked on top of each other.
With a torch, we heat the underside of the roll as we move forward. The bitumen turns liquid and fuses into the base ply. When a black bead squeezes out along the whole seam, the weld is complete. With a self-adhesive product, we peel off the film and press the sheet onto the base ply.
At the base of the parapets
The parapet is the low wall that surrounds the roof. The membrane turns there from horizontal to vertical, and sloppy roofs often leak at that spot. A well-made upturn brings together five things:
- a tapered piece at the bottom of the wall, which spares the membrane a right-angle fold
- a separate base ply for the upturn, which climbs the parapet
- a finish ply cut separately, distinct from the one covering the roof
- enough height to stay above water or slush
- a metal flashing on top of the parapet, which keeps water from getting in from behind
Frequently asked questions
How many days does it take to cover a plex roof?
A plex roof is often covered in a few days. The time varies with the area, the tear-off work and the weather. A deck in worse shape than expected can stretch out the job.
Does the torch put my building at risk?
The fire risk does exist, and trained crews contain it with known measures. Have those measures described to you and ask for proof of insurance that covers torch work. Your own insurer can tell you whether it has requirements.
Can the membrane be installed in cold weather?
The torch copes with cold better than self-adhesive membranes do. Temperature limits come from each manufacturer. For a late-season job, ask us how we will respect them.