Two lists of materials
These lists apply to a flat or low-slope roof, meaning a roof with a slope under 2:12.
On an existing building
For existing buildings, the City lists the allowed materials.
- asphalt, fibreglass or real wood shingle
- heat-welded or self-adhesive membranes
- enamelled metal, or metal painted and baked at the factory
- clay, slate, concrete or fibre cement tiles, or a similar synthetic product specifically designed as roofing
- galvanized sheet metal, installed Canadian style, pinched seam or batten seam
- copper
- zinc
- green roof
- glass
The list published for existing buildings sets no SRI threshold and says nothing about colour. It also does not name tar and gravel roofing. The City page does not say whether that roofing can be redone as is on a roof already covered with it. If that is your case, ask the permit counter before accepting a quote.
On new construction
For new construction, the City list is shorter.
- a material with an SRI of at least 78, confirmed by the manufacturer's specifications or by a professional's opinion
- a green roof, meaning a vegetated roof
- a combination of these coverings
The SRI measures how well a material sends the sun's heat back. The number is on the product data sheet.
Decks and mechanical equipment
The City provides one exception. Material requirements do not apply to the part of the roof taken up by mechanical equipment, such as an air conditioner or a heat pump, or by a deck.
Permit, fees and documents
The City states that in Lachine, maintaining or repairing a flat roof needs no permit. A permit is required to replace the covering, to change the structure, or as soon as the work touches the insulation.
Review fees are $9.80 per $1,000 of work, with a minimum of $167.40 for a strictly residential building. The minimum is $491.70 for a commercial, industrial, institutional or mixed-use building.
For a flat roof, the City asks for:
- the quote or a cost estimate grid, taxes included
- the certificate of location
- the technical data sheet for the planned materials, with the SRI
- a structural plan approved by a professional, when the law requires it
- any other document useful to the review
This document list makes no distinction between existing and new buildings. The data sheet with the SRI is on it even though no threshold applies to an existing roof. Ask us to hand it over with the quote.
Frequently asked questions
Is a white roof mandatory in Lachine?
For new construction, the City requires a material with an SRI of at least 78, a green roof or a combination of the two. For an existing building, the published list sets no SRI threshold.
Can a tar and gravel roof be redone in Lachine?
The list published for existing buildings does not name this roofing. The Lachine permit counter, at 1800, boulevard Saint-Joseph, can confirm what is accepted for your building.
How do you check a flat roof without going up?
Stay off the roof. Look at the top-floor ceilings, photograph the stains and note when they appear. We take care of inspecting the roof itself.
Official sources, consulted October 3, 2026: