Specialty Finishes
Basement Waterproofing (Interior) — Toronto & GTA
Interior waterproofing for basements with chronic moisture, seepage, or vapour issues.
About this service
Interior basement waterproofing is a different job than exterior excavation. We work on the inside of the foundation wall and the slab, using crystalline waterproofing coatings, elastomeric membrane systems, and in some cases interior drain tile tied to a sump. The appropriate approach depends on the symptom: efflorescence (white powder on the wall) is a vapour issue; wet spots and streaks after rain are hydrostatic pressure; a cold musty smell is usually both. We diagnose first, then specify. For many GTA basements, a well-applied interior crystalline treatment combined with proper drainage and sealing of the slab-to-wall cold joint resolves everything the owner was worried about, at a fraction of the cost of exterior excavation. For more severe cases, we're honest about when exterior work is the right call and will refer accordingly.
Our process
- 01In-home assessment and moisture mapping
- 02Diagnostic test (vapour vs. hydrostatic vs. both)
- 03Written specification of the appropriate system
- 04Surface prep and wall repair
- 05Crystalline or membrane application
- 06Cold-joint and penetration sealing
- 07Optional sump and drain-tile tie-in
- 08Final moisture reading and handover
What's included
- ●Diagnosis-first approach — no one-size solution
- ●Crystalline waterproofing coatings for walls
- ●Elastomeric membrane systems where appropriate
- ●Cold-joint sealing (slab-to-wall)
- ●Interior drain tile and sump integration
- ●Honest referral when exterior work is needed
- ●Compatible with subsequent floor coatings
- ●Reduces basement humidity and musty odour
Ideal for
- ●Older GTA homes with chronic basement moisture
- ●Basements with efflorescence on foundation walls
- ●Pre-finishing waterproofing before basement renovation
- ●Suite basements where moisture control is required
- ●Any basement with musty odour from the slab-wall joint
Questions people ask
Do you excavate from outside?+
No — we focus on interior waterproofing and refer out when exterior excavation is the right call. Most GTA basement issues respond well to interior treatment.
Can I finish the basement after?+
Yes — that's often the whole point. Our interior waterproofing systems are compatible with subsequent framing, flooring, and finishes. We coordinate the sequence.
What if I have an active leak during rain?+
That's a hydrostatic issue — we handle it with a combination of wall treatment and interior drain-tile systems where appropriate. For severe active leaks, we'll flag whether exterior work is needed.
We serve these cities
Each city page combines basement waterproofing details with local context for that area.