Basement Waterproofing in Montreal — Keep Your Basement Dry Year-Round
A dry basement starts with proper waterproofing. Nael Construction provides interior and exterior basement waterproofing across Montreal, Laval, and the South Shore. With Montreal’s heavy rainfall, spring thaws, and clay-rich soil, basement waterproofing is one of the best investments you can make in your home. Get a free assessment.
Interior vs Exterior Waterproofing
- Exterior waterproofing: The gold standard. We excavate around your foundation, apply a waterproof membrane, install a French drain, and backfill with gravel. Stops water before it reaches your foundation. Cost: $8,000–$20,000 for full perimeter. Lifespan: 30–50 years.
- Interior waterproofing: We install an interior French drain beneath your basement floor slab, connected to a sump pump. Manages water after it enters — doesn’t stop it at the source. Cost: $5,000–$12,000. Best for: homes where exterior excavation isn’t possible (attached garages, walkways, decks).
Signs Your Basement Needs Waterproofing
- Water on the floor after rain or snowmelt
- Damp or musty smell in the basement
- Efflorescence (white chalky residue) on walls
- Mould or mildew on walls, baseboards, or stored items
- Cracks in foundation walls (horizontal cracks are especially serious)
- Bowed or bulging walls
- Rust on appliances or metal shelving
- Peeling paint or bubbling drywall
Our Waterproofing Process
- Inspection: We assess your basement, identify water entry points, and check for structural issues
- Excavation (exterior): Trench dug to footing level around the foundation
- Foundation repair: Cracks sealed with hydraulic cement or epoxy injection
- Membrane application: Liquid rubber or sheet membrane applied to foundation walls
- Drainage board: Dimpled membrane installed to protect waterproofing and channel water down
- French drain installation: Perforated pipe in gravel bed at footing level
- Backfill: Clean gravel backfill, graded away from foundation
- Sump pump (if needed): Installed to pump collected water away from the house
Waterproofing Costs in Montreal (2026)
- Exterior — full perimeter: $8,000–$20,000
- Exterior — one wall only: $2,500–$6,000
- Interior — full perimeter: $5,000–$12,000
- Foundation crack injection: $400–$800 per crack
- Sump pump installation: $1,500–$4,000
- Battery backup for sump pump: $500–$1,200
- Backwater valve: $1,500–$3,000
Why Montreal Basements Need Waterproofing
- Clay soil: Montreal’s marine clay holds water against your foundation instead of draining it away
- Freeze-thaw cycles: Water in soil expands when frozen, creating hydrostatic pressure that forces water through foundation cracks
- Spring thaw: Rapid snowmelt saturates the ground — without proper drainage, water finds your basement
- Aging foundations: Many Montreal homes (pre-1970) have no waterproofing at all — just bare concrete or crumbling parging
FAQ: Basement Waterproofing
How long does basement waterproofing take?
Exterior waterproofing takes 3–7 days for a full perimeter. Interior takes 2–5 days. Foundation crack injection takes 1–2 hours per crack.
Is basement waterproofing worth the cost?
Yes. A dry basement adds usable living space (potential bedroom, home office, gym), prevents mould-related health issues, protects stored items, and increases home value. The cost of NOT waterproofing — foundation damage, mould remediation, ruined belongings — is far higher.
Do I need a permit for basement waterproofing?
Exterior waterproofing typically requires a permit in Montreal boroughs. Nael Construction handles all permitting.
Get a Free Waterproofing Assessment
Nael Construction is an RBQ-licensed general contractor with 10+ years of foundation and waterproofing experience in Montreal. Contact us for a free on-site evaluation.
Related: French Drain Installation | Basement Finishing | Yard Drainage Guide