Flat Roofing near you

Each system has its own installation method, detailing and repair technique, and not every roofer works with all of them. Ask which membrane is on your roof now, and why a contractor recommends keeping the same type or switching to another.

A flat roof is never truly flat. The deck or the insulation is sloped so that water runs to interior roof drains, to scuppers through the parapet or to gutters at the edge. When that slope is lost because the structure has sagged, the insulation has compressed or a drain sits higher than the surface around it, water stays in puddles after the rain has stopped. Standing water speeds up wear on the membrane, adds weight and, in winter, turns into ice that works at seams and flashing.

Interior drains carry a lot of meltwater during thaws, and a drain blocked by leaves, gravel or ice can back water up against flashing that was never meant to sit under water. A roofer can correct low spots with tapered insulation or an added drain, and replace clogged or broken strainers.

Many older plexes have a shallow space between the top-floor ceiling and the roof deck, sometimes with little insulation and small vents at the front or back. Warm, moist air leaking up from the apartments can condense under the cold deck in winter, soaking insulation and rotting wood even when the membrane is sound. That is why water on a top-floor ceiling doesn't always mean the roof has a hole.

A roof replacement is a good moment to rethink insulation. One approach keeps a ventilated cavity with insulation below it and depends on a well-sealed ceiling. The other places rigid insulation on top of the deck, under the new membrane, which keeps the structure warm and can build in slope for drainage at the same time. The right choice depends on the building, any limits on roof height and what is already in the cavity, so ask the roofer to explain the plan, and bring in an insulation contractor if air leaking from below is part of the problem.

In Montreal, the City's page on renovating a flat or low-slope roof says that repairs and maintenance don't need a permit, but replacing the roof covering or changing the roof structure does. The new covering must be white, painted white, coated with a reflective finish or topped with white gravel, meet a minimum solar reflectance index set by the borough, or be a vegetated roof, for which you apply at the permit counter. The parts of the roof taken up by mechanical equipment or a terrace are exempt. The details vary from one borough to another, so check yours before signing a contract.

Toronto's Green Roof Bylaw set green roof requirements for new development or additions of more than 2,000 m² of gross floor area and exempted residential buildings under 6 storeys or 20 m high, which left out ordinary houses. The City's permit guide now states that as of November 3, 2025, the bylaw is no longer applicable law under the Ontario Building Code and green roofs are voluntary; a building permit is still required to build a new green roof or materially alter an existing one.

In Quebec, a roofing contractor must hold an RBQ licence with specialized contractor subclass 7.0, which covers insulation, waterproofing, roofing and siding. In other provinces, ask your municipality about permits before a full replacement, especially if the structure, the drainage or the height of the roof will change.

Winter is hard on low-slope roofs: ice forms in low spots, snow drifts against parapets, and repeated freezing and thawing opens small cracks at seams and flashing. A check in spring, once the snow is gone, and another in fall, before leaves and the first snow reach the drains, is a sensible routine for plex owners. Leave the walking to the roofer: a wet or icy roof with a low parapet is a real fall hazard, so look from a window or roof hatch at most.

A single leak at a flashing, a split seam or a punctured spot on an otherwise sound membrane can usually be repaired with the same material. Repairs make less sense when problems show up all over the roof, when the insulation underneath is wet over large areas, or when the membrane has lost its flexibility and cracks wherever it is disturbed.

Before deciding, a roofer may cut small test openings or use moisture detection to find out how much of the insulation is wet. Laying a new membrane over an old, wet roof traps that moisture, so ask whether the plan is to strip down to the deck, and whether Montreal's white-roof rules or other local requirements will apply to the new covering.