A finished basement is the most cost-effective square footage you can add to a Montreal home. It is also the most failure-prone if the moisture, ventilation, and insulation strategy are wrong. The half-finished basements we see most often share the same three problems: water intrusion the prior contractor "drylocked over," batt insulation packed against a cold foundation wall (a frost-line condensation trap), and bedrooms framed without a compliant egress window. We don't skip any of those.
What we handle
- Moisture diagnosis and remediation: interior drainage mat, sealing of cracks, exterior repair when warranted
- Insulation: closed-cell spray foam on foundation walls and rim joists, vapour-managed assemblies
- Framing, drywall, painting, flooring (engineered hardwood, LVT, carpet)
- Egress windows for legal basement bedrooms — opening sized to code, well and ladder installed, permit filed
- Bathrooms: full rough-in, pump systems where the sewer is above slab, finished tile work
- Wet bars and kitchenettes, including in-law suite layouts
- Home theatres: acoustic treatment, dedicated circuits, in-wall speaker pre-wire
- Electrical panel upgrades when capacity is short
- HVAC distribution and dehumidification strategy
What it costs
Most finished basements in Montreal and the West Island land between $35,000 and $110,000. A 600–800 sq ft family room with mid-grade finishes, recessed lighting, and a powder room runs about $35K–$55K. A 1,000+ sq ft basement with a full bathroom, wet bar, egress upgrades, built-ins, and home-theatre prep runs $80K–$110K. In-law suites with separate cooking and laundry typically reach the top of the range or above.
How the schedule works
From signing, expect 10–20 weeks: 2–6 weeks of design, engineering, and permit filing; 8–14 weeks on site. We do interior framing first, then rough-in plumbing and electrical, then inspections, then insulation, drywall, and finishes. We do not start finishes until the basement has run through a wet weekend with no water intrusion.
Recent basement projects
- DDO full house — Basement family room and bath
- 10 Applewood, Hampstead — Lower-level rework as part of full home
A note on insurance and warranty
Every finished basement we deliver carries the standard Revohouse one-year workmanship warranty plus the manufacturer warranties on installed assemblies. We document the as-built mechanical, drainage, and waterproofing layout so future homeowners know what is behind the drywall. For in-law suites and rental units we also coordinate with your insurer to confirm that the renovated configuration is on cover before turnover. None of this costs extra — it is part of how we close a basement project.