Homeowner guide
French drain in Montreal: when to replace it and what to expect
If you see humidity, cracks or white stains on your basement walls, the French drain around your foundation has probably stopped draining water properly. Replacing it usually takes 3 to 7 working days, depending on yard access.
When you need it
The signs to watch for
- Water or humidity in the basement after rain or snowmelt
- White stains (efflorescence) or cracks on foundation walls
- Persistent musty smell that ventilation does not fix
- Foundation built before 1980 or a drain never replaced
- Lawn that stays soaked near the building
How we work
Step by step
- 01We start by identifying the cause: ground slope, water outlets, visible signs of infiltration in the basement.
- 02We excavate along the foundation while protecting access, steps, the balcony and the existing landscaping.
- 03We clean the foundation down to bare concrete to spot cracks, honeycombing or weak points to treat first.
- 04We apply the proper waterproofing membrane so water can no longer reach the concrete.
- 05We install the new drain with clean stone and geotextile, with slope verified toward the outlet.
- 06We backfill in compacted layers with a positive slope that sends water away from the building.
Cost and time
What affects price and timeline
Every job is different. Here are the concrete factors that move the estimate up or down. The fast quote tool accounts for these points.
What affects the price
- Length of foundation to expose (25 ft vs 50 ft home vs full perimeter)
- Depth of the existing drain — deeper means longer dig
- Yard access for equipment: open ground vs landscaping to protect
- Foundation condition once exposed — cracks to repair or not
- Adding a sump pump or an access well to the drain
What affects the timeline
- 3 to 7 working days for a standard residential drain
- Less if only one side of the foundation is affected
- More if the foundation has cracks to repair or existing stone is clogged with clay
- Working season: mid-April to mid-November in Montreal — while the ground is unfrozen
Your side
What you prepare for us
- Photos of infiltration, cracks, efflorescence or damp areas in the basement
- Mention of any previous repair or existing drain
- Clear access to the outside foundation (move vehicles, furniture, bins)
Our rules
What we will never do
- Backfill without verifying the drain slope with a level
- Cover a visible foundation crack without treating it first
- Leave a trench open without fencing overnight
- Reuse the clogged stone from the old drain
The result
What you end up with
- New French drain that moves water away instead of holding it against the foundation
- Basement stays dry — the proof is the next heavy rain
- Ground backfilled with slope sending water away from the building
- Work documentation handed over for your records or a future resale
Frequent questions
Your answers
How long does a French drain last?
A drain installed properly — clean stone, geotextile, positive slope, clear outlet — lasts 25 to 40 years. Drains that fail before 20 years were almost always installed without geotextile or with insufficient slope.
Can this be done in winter?
Once the ground freezes, no. The working season is mid-April to mid-November in Montreal. If you have an active leak in winter, we can do a temporary interior patch to get through the winter and replace the exterior drain as soon as the ground thaws.
Do I need a municipal permit?
For a like-for-like drain replacement, usually no. If we modify the outlet (adding a pump, connecting to the municipal storm sewer), a permit may be required. We check with your borough before starting.
Will my landscaping be damaged?
We only excavate the strip needed along the foundation. Nearby shrubs and plants are identified beforehand and either transplanted or protected. Cut grass does not replant — plan on reseeding after the work.
How do I know if I need a new drain or just a repair?
A visual inspection is not enough — you often need to expose a section to see the real condition. That is why we give you 3 prices: the a1 tier (What's urgent) covers a localized repair, A1 (Everything that needs doing) covers full replacement, and A1+ (While we're at it) adds a sump pump and regrading.
What warranties do you offer?
Our work is guaranteed against installation defects. The performance warranty depends on the chosen tier and is stated in the quote. RBQ 5825-9060-01, APCHQ member.
See also
Other A1 methods
Excavation
For an addition, pool, shed or garage, excavation usually takes 1 to 5 working days depending on depth and yard access. The golden rule: confirm buried services and soil stability before the first bucket-load.
Read the guide
Grading
Grading corrects slopes, removes unstable soil and creates a solid base before pavers, lawn, concrete or landscaping. A typical residential yard takes 1 to 5 working days depending on area and how much imported material is needed.
Read the guideYour next step