Flat roof in Sainte-Dorothée

Where the City places the apartment buildings

The land use plan places mid-rise multi-family buildings in the northern part of the area. The plan says nothing about their roofs.

On the heritage side, the City's inventory lists 54 principal buildings in Sainte-Dorothée, 4 of which have a flat roof. This figure applies to heritage buildings only. The page roofing in Sainte-Dorothée gives the rest of the picture.

The slope that makes a roof flat

The Code sets the limit at a slope of 16.7%, or 2:12. At that slope or below, the roof is flat. The slope we measure belongs in our quote.

Article 380, and what it leaves open

For a flat roof, article 380 requires a green or white covering, or one with a solar reflectance index of at least 78. The Code does not address the case of an existing roof redone identically. The full list of options is on the area page.

The text does not say whether a dark membrane already in place can be replaced with the same one. Write to the Service de l'urbanisme (urban planning department) before requesting quotes, and keep its answer.

If you choose the reflectance index, the Code requires proof: the manufacturer's specifications or a professional's specifications.

The membranes the Code allows

Article 379 lists the coverings allowed in Laval. For a flat roof, the list names, among others, TPO, EPDM, multi-ply tar membrane, modified bitumen elastomeric membrane, heat-welded or self-adhesive membrane, and gravel laid on an authorized membrane.

Taller buildings

Another article of the Code, article 141, deals with the structure. The structure must be able to carry an extensive green roof when the building has more than three storeys, the roof of the building or its extension exceeds 250 m² and the roof is flat. The article includes exceptions. Article 141 speaks of the design of the structure and does not say what applies to an existing building where only the membrane is redone.

A heritage address: the exemption

The Code includes a territory of heritage interest in Sainte-Dorothée. Changing the roofing materials of a principal building there may require a PIIA (site planning and architectural integration program). The Code exempts replacement with the same material of a similar colour, or with a material that preserves or restores the original or traditional characteristics. The Code also exempts renovation work on a flat roof from the PIIA.

Being exempt from the PIIA changes nothing else. The permit and article 380 keep their own rules. For the permit, the City looks at whether the material of a residence changes, without defining what the same material is.

What you can note without climbing

Do not go up on the roof, even a flat one. From inside, record the stains on the top-floor ceiling, with the date and the unit.

Frequently asked questions