Flat roof in Laval-des-Rapides

What the City says, and what it does not

The City lists Laval-des-Rapides among the older neighbourhoods where plexes make up a larger share. It does not describe their roofs and gives no count of flat roofs in the neighbourhood.

Its heritage inventory provides a limited benchmark. Of 46 main buildings listed, 15 have a flat or low-slope profile. This figure only applies to heritage buildings.

The page on roofing in Laval-des-Rapides gives the text of the rules.

Article 380 in brief

On a flat roof, article 380 calls for a green roof, a white covering, a material with a solar reflectance index of 78, or a mix of these solutions. The article is silent on an existing roof redone exactly as before.

Under the Code, your roof is flat if its slope does not exceed 2:12, that is, 16.7%.

Proof of the reflectance index

The Code says how the index is shown: by the manufacturer's specifications or a professional's specifications.

Ask us for three things:

• the membrane's technical data sheet, with the solar reflectance index written in numbers
• the exact product name in the quote, the same as on the data sheet
• a copy of the data sheet, to keep with the building's invoices

We can also propose a white material, a reflective coating or white ballast. The article names these options separately, without attaching an index to them. Have the quote state which of the article's options is chosen.

The coverings the Code allows

Another article, 379, lists the roof coverings allowed in Laval. For a flat roof, it includes TPO and EPDM membranes, multi-ply tar membrane, elastomeric membrane, heat-welded or self-adhesive membrane, gravel laid over a permitted membrane and green roofing, among others.

Being on this list does not settle everything. On a flat roof, the covering must also meet article 380.

The question of the existing roof

Your plex has a tar and gravel roof or a dark membrane, and you want to redo it as is? Article 380 sets out an obligation for buildings with a flat roof. The article does not say whether this obligation applies at the time of a roof replacement.

The permit does not help settle it. For a residence, the City requires none when the covering is replaced with the same material, but the Code states that a permit exemption does not release anyone from the obligation to comply with the applicable regulations. Conversely, a new material requires a permit for a residence. The City does not define what same material means, so ask it whether switching to a white membrane counts as a change.

Put these questions to the Service de l'urbanisme (the City's planning department) before signing, and ask for a written answer.

What you can note without climbing up

Do not climb onto the roof, even if it is flat and a hatch leads to it. From the top unit, note where the rings on the ceiling are and after which rain they appeared.

Frequently asked questions