How a commercial roof differs from a house
On a house, the roof protects a family and is replaced in a few days. On a commercial building, it protects tenants, stock, equipment and sometimes a production line. A leak can shut down a business or affect several occupants at once.
The core logic is the same as for any roof repair: find where the water comes from, fix the cause, then decide whether the roof should be repaired or replaced. What changes is everything around that decision.
- Size. Work on a large roof often spreads over several weeks, and sometimes over more than one budget year.
- Equipment. Mechanical units and their supports pierce the membrane in many places.
- Foot traffic. Technicians go up all year to service the mechanical units. Every visit can damage the membrane.
- Structure. Steel or concrete decks and long spans impose limits on weight and fastening.
- Occupants. The job site has to coexist with people who work, sell or live under the roof.
- The decision. It goes through a budget, a board or an owner who wants comparable quotes.
The buildings involved
"Commercial" covers very different buildings.
- Shops and strip malls. One air conditioning unit per tenant, and restaurant kitchens that exhaust grease.
- Warehouses and industrial buildings. Very large surfaces, few penetrations, light steel decks.
- Office buildings. Concentrated mechanical equipment, parapets, sometimes an accessible roof.
- Apartment buildings and condos. One roof shared by several households, with decisions made as a group.
In Montreal, these buildings are not in the same places. Large warehouses and industrial buildings are found in areas such as Saint-Laurent, Anjou, Lachine and the east end of the island. Street-front shops, often with apartments above, line the main streets of central neighbourhoods. Apartment buildings and condos are everywhere.
Location changes the job. A roof squeezed between two neighbours above a busy sidewalk is not handled like a warehouse roof surrounded by parking.
Questions to settle before asking for quotes
When we visit a commercial roof, we ask questions a manager should be able to answer. Preparing them ahead of time gives more precise quotes.
- How old is the roof and what system covers it?
- Have there been repairs, and where?
- Are there plans, an inspection report or a maintenance log?
- Is a warranty still in force, and under what conditions?
- Which areas of the building cannot tolerate noise, odours or interruptions?
- Where can we go up, and where can we store materials?
If you do not have these answers, a documented inspection is the right starting point. The inspection also shows whether the problem is localized or whether the insulation is wet over a large area. In the second case, the project changes completely.
Rules, permits and white roofs
In Montreal, the rules vary by borough, building type and the nature of the work. According to the City of Montreal, replacing the covering of a flat roof requires a permit in most boroughs. Minor repairs and maintenance generally do not.
During a replacement, several boroughs require a white roof, a reflective material or a green roof. The required solar reflectance index ranges from 56 to 82 depending on the borough. This requirement weighs directly on the choice of membrane. Heritage buildings and heritage areas have additional standards.
Check the requirements with your borough before finalizing the specifications. Your insurer may have its own, and structural questions belong to an engineer.
Who does what
On a small project, we visit, propose and do the work. On a large roof, an independent professional such as an engineer, an architect or a roofing consultant often prepares the specifications and oversees the work.
In every case, a construction contractor must hold a licence from the Régie du bâtiment du Québec (RBQ). The register of licence holders is public on the RBQ website. Ask us for our RBQ licence number and check it in that register, as with any contractor.
A project from condition survey to closeout
A project run without urgency goes through the same steps, whether the roof is small or large. At each one, you should receive something in writing.
- Condition survey. An inspection and a report on the state of the membrane and insulation.
- Scope of work. Repair, replace a section or replace the whole roof.
- Checks. Borough, structural and insurer requirements.
- Specifications. The work described in writing, the same way for everyone.
- Quotes. We visit the roof and price the same work as the other bidders.
- Contract. Scope, schedule, warranties and how surprises are handled.
- The work. The roof is redone in sections, with progress reports.
- Closeout. We show you the result in photos. You list the corrections needed and receive the warranties.
Closeout is the last moment when everyone is still on site to fix a detail. This step is often skipped.
What a commercial quote should spell out
A single lump-sum price on one page is not enough for a building. Along with the description of the work, ask that every quote, ours and the others, state:
- what is excluded from the price,
- the length of the job and the proposed period,
- the name of the person in charge on site,
- who applies for the permit, you or the contractor,
- the RBQ licence number and proof of liability insurance.
A quote that hides its exclusions is not a better deal. It is only less complete.
Treat the roof as an asset
A commercial roof is managed over its whole life. A manager who knows the age of the roof, its condition and the likely replacement date can set money aside and choose the season. A manager who waits for the leak is stuck with the calendar, often at the worst time of year.
When a leak happens anyway, send no one onto the roof. Limit the damage inside, note the location and time, take photos and ask us for a temporary repair. Notify your insurer. The decision to repair or replace comes later, calmly, with a report in hand.
Some moments call for a closer look even when nothing leaks: before buying a building, when a warranty nears its end, before installing new rooftop equipment, when a new tenant such as a restaurant changes what the building exhausts, and after a violent storm or high winds.
The documents to keep
A well-managed roof has its own file. The file follows the building, not the person in charge of it. It holds roof plans showing drains and equipment, inspection reports, the specifications and contract for the last replacement, manufacturer and labour warranties with their conditions, product data sheets, and a maintenance log with dates, findings, photos and invoices. Store it where your successor will find it.
Frequently asked questions
Does a commercial roof last longer than a residential roof?
A commercial roof does not necessarily last longer than a residential one. Lifespan depends on the system, the manufacturer and the quality of installation, not on how the building is used. A commercial roof does get more foot traffic and more penetrations, so maintenance matters more.
Can you repair one section without replacing the whole roof?
Yes, a section can be repaired on its own when the damage is localized and the rest of the membrane is sound. If the insulation is wet over a large area or leaks keep multiplying, repairs only push back the deadline. An inspection settles the question.
Can the work be done while the building is occupied?
Yes, most commercial roofing jobs are done on occupied buildings. The roof is redone in sections, and noisy or smelly work is scheduled around occupancy hours. Tell us about it when we prepare the quote.
Do you need a permit to replace a commercial roof in Montreal?
In most Montreal boroughs, replacing the covering of a flat roof requires a permit. The rules vary by borough and building type. Confirm with yours before signing a contract.