The three approved roofing options
The City's page for Saint-Laurent lists the materials and roof types allowed on a flat or low-slope roof:
- white gravel
- a material with a solar reflectance index (SRI) of at least 78, certified by the manufacturer's specifications
- a green roof
These rules come on top of what applies to any repair in Saint-Laurent, where maintenance needs no permit.
The SRI measures how well a surface sends back the sun's heat. The higher the number, the cooler the roof. The number is not a visual impression. A pale membrane does not necessarily reach 78. Saint-Laurent's list does not even name "white material". Apart from white gravel and a green roof, only the index, certified on the manufacturer's sheet, counts.
The page does not say whether a dark membrane covered with white gravel must meet other conditions, or how that gravel is defined. If that is your choice, have it approved at the permit counter.
Parts of the roof that are exempt
According to the City, Saint-Laurent's three options do not cover the part of the roof taken up by a deck or by mechanical equipment, such as an air conditioner or heat pump.
The page does not say how these areas are measured. We note them during the visit, so you do not need to go up on the roof.
When the permit applies
For a flat roof, the borough separates three situations:
- maintaining or repairing the roof, adding tar for example, needs no permit
- touching the insulation or structure needs a permit
- installing or replacing the roofing needs a permit
Fees published by the City
The review fee depends on the estimated cost of the work, at $9.80 per $1,000. The minimum is $167.40 for a strictly residential building and $491.70 for a commercial, industrial, institutional or mixed-use building.
The estimate must include all costs related to the work, taxes included. Fees are non-refundable.
The data sheet is the key document
For a flat roof, the City asks for a data sheet that describes the materials and gives their SRI. That sheet shows the roofing meets the 78 threshold. Ask for it to come with the quote.
The file also includes the quote or a cost estimate grid with taxes, the certificate of location, and any other document useful for the review.
White or green roof: the counter is recommended
For a white roof or a green roof, the City recommends going to the Saint-Laurent permit counter, 777, boulevard Marcel-Laurin. It states that you can also apply online.
The page does not detail requirements specific to green roofs, such as whether the structure can carry the weight. A green roof should be discussed with a professional and with the counter before any quote.
Frequently asked questions
What SRI is required for a flat roof in Saint-Laurent?
A flat roof redone in Saint-Laurent with a reflective material needs an SRI of at least 78, certified by the manufacturer's specifications. White gravel and a green roof are the two other options the borough allows.
Can I keep a grey tar and gravel roof?
As long as you maintain or repair that roof, the City's page requires no permit. When the roofing is replaced, the new roof must be one of the three approved options. The permit counter can confirm what applies to your building.
Does the area under my rooftop deck have to be white?
No, the part of the roof covered by a deck is exempt from Saint-Laurent's material requirements, like the part taken up by mechanical equipment.
Official sources, consulted October 3, 2026: