Roof Repair vs. Replacement in Montreal: Costs & Warning Signs (For Flat & Sloped Roofs)

Rooftops in Montreal suffer a lot of wear and tear over their lifetime. In the winter, temperatures often dip under -10°C, and heavy snowfall packs the roof with layers of snow, ice and sleet. Come summertime, the roof’s surface is hit with successive heatwaves, torrential rainstorms, and strong winds. These conditions often cause damage that requires prompt repairs and in certain cases, complete replacement of the roof. 

As a homeowner in Montreal, you may be wondering if your roof is in need of repair or replacement. We’re here to help! Read on for everything you need to know.

Here are some of the questions we will cover in this article : 

• What are the signs that you need to repair a flat roof?

• What are the signs that you should replace a flat roof?

• How to know whether you should repair a sloped roof?

• What signs point to needing a replacement of your sloped roof?

• What are the costs for repairs or replacement projects?

Flat roofs in Montreal : what you need to know about repairing and replacing them

Source : DK Toitures Inc.

Many residential and commercial buildings in Montreal are coiffed with flat roofs. This type of roofing structure is not completely flat, but it has such a low slope that you can barely see it. Flat roofs are very common in Montreal, notably for safety reasons, as snow falling from sloped roofs exposes buildings and passersby to potential damage and injury. 

There are different kinds of roof covering materials meant for flat roof structures. These materials play many crucial roles, the most important of which is being watertight. 

Most common materials for flat roofs : 

There are a number of options available in terms of flat roof materials. What they all have in common is that they help keep the rooftop surface airtight and watertight. For this reason, roof shingles, such as those often used on sloped roofs, are not a viable option on a flat surface. Here are the materials you can choose from : 

Flat asphalt and gravel roof

These types of rooftops contain several layers, including a succession of gravel, liquid asphalt and, asphalt felt. They represent an affordable option, at $7 to $12 per square foot. However, the installation must be done by a professional, as handling materials such as molten asphalt is a risky endeavour. Asphalt rooftops tend to have a lifespan of about 10 to 15 years. 

Elastomeric Membrane Roof System

An elastomeric roof is a dual-layer roof, including a base sheet and a layer of gravel at the top. At $9.50 to $15 per square foot, it costs a bit more than an asphalt and gravel roof, but it has a much longer lifespan, at 25 to 40 years. 

Elastomeric Membrane Roofing - 7 Facts You Must Know

Single-Ply Flat Roof Membrane : TPO

There are two kinds of single-ply flat roof membranes, one of which is Thermoplastic polyoelefin (TPO). This rooftop material is easy to install and highly durable. TPO membranes are also eco-friendly, as they are fully recyclable and made from non-toxic materials. Budget $7 to $12 per square foot for a TPO flat roof.

Single-Ply Flat Roof Membrane : EPDM

The other type of single-ply flat roof membrane available on the market is Ethylene, Propylene and Diene Monomer (EPDM). Contrary to a TPO membrane, an EPDM membrane can’t be recycled as easily. However, it has a long lifespan (at least 50 years), which makes it a great option. It costs between $9 and $12 per square foot. 

Signs that your flat roof needs to be repaired

Source : Dori Construction Inc.

The key to a long lifespan for your flat roof is maintenance. At least once a year, go up and check for different signs of wear and tear that could require easy repairs, thus preventing larger issues. This is what you should be looking out for : 

• Parts of the roof that are coming apart or areas that seem warped.

• Water accumulating in certain areas (could be a problem with the drain).

• Joints that are not weatherproof. 

• Missing gravel (should be remedied quickly).

• Torn membrane (needs to be patched).

How to tell whether you need a new flat roof

In some cases, simple repairs won’t be enough, and you’ll have to replace the whole rooftop surface. Here are the signs that your flat roof needs to be changed : 

• Structural issues in the home. 

• Water infiltration creeping into the rooms.

• Age of the roof (materials have reached the end of their lifespan).

• Extensive damage of the rooftop material.

• Gutters that are constantly filling with rooftop debris.

Checklist : 10 signs that you need to repair or replace your flat roof 

Bring this list with you when you go up on the roof (or hire a pro if you don’t feel confident to carry out this inspection). Be sure to take the proper precautions when climbing up at heights like this (non-slip footwear, safety harness, stable ladder, good weather conditions). 

If you write yes to more than 4 of the signs in this table, you’ll want to think about replacing your flat roof. If you check one or two, make sure to carry out the repairs quickly, as any type of damage on a roof can turn into an urgent situation if not taken care of swiftly. Always hire a professional roofer for this type of job.

How much does it cost to replace a flat roof in Montreal ?

Here is a table presenting the costs to install a new flat roof in Montreal : 

Source : Flat Roofing Costs: How Much Should You Budget in 2025? 

Cost to repair a flat roof in Montreal 

In terms of repairs, the budget will depend on a number of factors, including the size of the issue that needs to be repaired, the roof components in question, the materials needed, and the urgency of the repair. You could be looking at $500 for a quick problem that could be fixed in under an hour or two, or $5000 to reinforce the roof’s structure. The only true way to know how much you will have to pay is to get in touch with contractors and have them present a quote. 

Here are more articles about flat roofs : 

• Flat Roof Systems - What Are Your Options?

• Flat Roofs Benefits - What are their key advantages?

• Flat Roof Insulation: Practical Tips and Advice

• How to Maintain a Flat Roof

Sloped roofs : what you should know about repairing and replacing them

Lots of Montreal homes are coiffed with sloped roofs, which have their own characteristics and maintenance regimen, different from that of flat roofs. Firstly, the structure holding the roof has a whole other shape. You’ll also notice that the materials used to cover the roof are very different from those used on a flat roof.

Find more info here : 

The Standard Roof Slopes | Reno Quotes

Most common materials for sloped roofs : 

Source : Toiture Métallique Montréal Inc.

Most sloped roofs found on homes in Montreal will be covered in asphalt shingles, wood shingles, metal roofing or stone tiles. Learn more about the different roofing materials available on the market, here is an article to look into: 

The Different Types of Roofing Materials to Choose From

Signs that your sloped roof needs to be repaired

As a homeowner, you should inspect your roof at least once a year. Climbing up onto a sloped roof is potentially dangerous, so you mustn’t take this task lightly. Hire an expert roof inspector, and if you decide to carry out the task yourself, apply a strict security protocol, the most important being that you have another person with you on the ground at all times in case something happens. 

Once on the roof, these are the signs that your sloped roof either needs to be repaired or replaced : 

• Your roofing material has reached the end of its predicted lifespan.

• You notice missing or broken shingles.

• Water is pooling in certain areas where it shouldn’t be.

• The gutters are full of roof material debris.

• The ventilation ducts are blocked.

• The soffits, fascia and flashing are in poor condition.

• Some parts of the roof are warped. 

• You find moss on the surface.

How to tell whether you need a new sloped roof

If the damage on your roof turns out to be extensive, a simple repair may not be enough to maintain proper living conditions in your home. These are the signs that your sloped roof has to be rebuilt entirely : 

• Water is infiltrating inside your home through the ceilings.

• Your home is suddenly very humid or very dry, when in the past, there were no such issues.

• Your electrical bills have steadily gone up recently. 

• There are cracks in the walls and upper floor’s ceiling.

• You find indications of severe damage, such as parts of the roof that are caving, 

Checklist : 10 signs that you need to repair or replace your sloped roof

Source : Toitures rodrigue inc

Use this list to determine whether your roof needs to be replaced or if a simple repair could do the job for the time being. Of course, you’ll need to validate this decision with a roofing expert, as this type of project should not be taken lightly.

How much does it cost to replace a sloped roof in Montreal ?

Check out this table comparing the cost per square foot for the most popular sloped roofing materials used on homes in Montreal : 

Source : Cost of Roof Repair 2025 - How much to budget?

Cost to repair a sloped roof in Montreal 

A full roof replacement will set you back at least a few thousand dollars, whereas a simple repair could cost $500. However, the fact is that even a repair may end up quite expensive. Roofing renovations are often complex and require proper equipment and materials. It’s hard to say how much your rooftop repair will cost without knowing the issue in question that needs to be fixed. This is something you will have to discuss with your roofing contractor.

In conclusion

Whether your Montreal home is equipped with a flat roof or a sloped roof, you need to take rooftop maintenance seriously. Set aside a budget for cleaning and repairs every few years and have an expert inspect your roof to prevent severe damage. When the time comes to replace your roofing material, look at the different materials available, make sure you get a permit for the work, and have a pro carry out the project. 

More articles about roofs to deepen your knowledge on the subject : 

• Roof Renovation Guide: Steps to Follow | Reno Quotes 

• Choosing Your Roof Shape: Flat, Sloped, or Mansard

• Roof Structures: Key Components and Building Guide | Reno Quotes 

• Altering the Slope of a Roof: Prep & Process | Reno Quotes