In short
On a Montreal plex, replacing the floor of an existing balcony with a fibreglass floor costs $3,000 to $12,000 per balcony. The difference comes mostly from removing the posts and railings, the height of the balcony and access to the site (hard-to-reach laneway, trees, machinery). Properly installed and fastened from underneath, a fibreglass floor easily lasts 20 to 35 years, and the manufacturer's warranty runs from 5 to 15 years, depending on the product. The work itself takes a few days.
In Montreal, plexes often have stacked balconies, exposed to sun, rain and snow. The floor is the part that suffers the most: it is the part that takes the water. When the balcony's structure is still sound, there is no need to redo everything: only the floor is replaced. This is what most people call "repairing a fibreglass balcony." Cam Construction has been doing this work since 1991, in Hochelaga, Rosemont, Villeray and the Plateau-Mont-Royal, among other areas.
Fibreglass or wood?
For a stacked, exposed balcony: fibreglass
For most Montreal balconies, stacked and exposed to the weather, we recommend a fibreglass platform. It is a proven material. It is durable and waterproof, it needs no maintenance, and it is not affected by humidity, snow or sun.
For character: wood, but sheltered
If you love the character of wood and maintenance doesn't scare you, a wood floor is still possible. On one condition: it must be covered, by the balcony above or by a roof. "Otherwise, water infiltration and rot are guaranteed," warns Cael Camirand, General Director of Cam Construction.
How much does it cost?
Here are the numbers to remember for the floor of a plex balcony in Montreal. Every balcony is different: only an on-site estimate gives the exact price.
| What you need to know | Usual figure |
|---|---|
| Replace the floor of an existing balcony with a fibreglass floor | $3,000 to $12,000 per balcony |
| Length of the work | A few days |
| Lifespan of a quality floor, properly installed and fastened from underneath | 20 to 35 years |
| Manufacturer's warranty | 5 to 15 years, depending on the product chosen |
Figures given by Cael Camirand, General Director of Cam Construction. The price is per balcony: on a triplex, every balcony counts.
What drives the price
- Removal. To replace a floor, the posts and railings have to be taken off, then put back. This is the main reason the price varies so much.
- Height and location. A ground-floor balcony on the street and a third-floor balcony at the back don't take the same effort.
- Access. In Montreal, there are many obstacles: hard-to-reach laneways, trees to work around. The floor pieces are custom-made, and machinery is sometimes needed to lift them up safely.
- Fastening from underneath. To fasten the floor properly, we remove the cladding under the balcony. It costs more, but it is what makes the floor last (see below).
- The product chosen. Not all fibreglass floors are the same: the manufacturer's warranty runs from 5 to 15 years, depending on the product.
What makes a fibreglass floor last
A good-quality floor, properly installed and securely fastened from underneath, easily lasts 20 to 35 years. Two things make the difference.
Fastened from underneath, on a sound structure
The floor must be fastened from underneath, on a sound, level structure. To do this, the cladding under the balcony has to be removed. It takes more time and more resources, so the price is higher. "It's really worth taking the time. It costs more, but it's better work, that will last a long time, look good and perform well," explains Cael Camirand.
If the structure is not sound, it has to be repaired before the floor is installed. For a balcony with damaged joists, see our balcony repair service.
No holes on top
The secret to keeping a fibreglass floor for a very long time is to avoid any holes in the top of the platform. Every hole is a possible way in for water. That is also why the floor is fastened from underneath.
Signs it's time to act
Many of the balconies we are called upon to repair were improperly built from the start. Here are the most common problems to watch for.
A slope toward the building
This is the most common issue we correct. Water must drain away from the wall. If it flows toward the building, it will eventually seep inside.
A floor that moves or flexes
This is often a sign that water has penetrated the balcony platform, or that there is an issue with the floor's support or fastening system.
Cracks in the fiberglass
Cracks can compromise the floor's structural integrity and waterproofing.
Holes in the top surface
Screws or anchors drilled through the platform allow water to reach the plywood and underlying structure. The sealant around these fasteners must be regularly inspected and maintained.
A loose or unstable railing
This is an immediate safety hazard. The railing must be properly secured, and its anchor points must be sealed without delay.
The rules in Montreal
According to the City of Montreal, most maintenance or repair work on a balcony does not require a permit. But if you use materials different from the original ones, for example fibreglass instead of a wood floor, you must inform your borough's permit counter before buying the materials, with a professional-quality plan. To build, enlarge, modify or replace a balcony, you need a permit, with rare exceptions. The details are on the City's page: Build or replace a deck, balcony, gallery or porch (checked in November 2026).
Rules and fees vary from one borough to another. We check what applies to your balcony and file the application for you. Learn more about our permit application service
Season and length of the work
Replacing a fibreglass floor is quick: a few days. This work can be done year-round, but we avoid January, February and March: access to the balcony is much harder and the work is more difficult.
Before you sign
- The RBQ licence. Check the contractor's licence with the Régie du bâtiment du Québec. Cam Construction's: 2854-6760-18.
- Certification. Cam Construction is an APCHQ-certified contractor.
- The permit. Ask who checks the borough's rules and files the application. At Cam Construction, we do.
- How the floor is fastened. Ask how the floor will be fastened. A floor fastened from underneath, on a sound, level structure, with no holes on top, will last much longer.
- The slope and the warranty. Make sure the slope carries water away from the building, and ask which product will be installed and what its manufacturer's warranty is.
