Interior Basement Waterproofing
A perimeter drainage channel, weeping tile, and sump pump system that intercepts groundwater before it pools on your floor. Completed in 1–2 days, no exterior excavation, with a lifetime transferable warranty.
Stop water damage before it becomes a flooding emergency
Interior basement waterproofing is a drainage management system installed along the inside perimeter of your foundation. A 12–18 inch strip of concrete is removed at the base of the walls, a perforated drainage channel is set in a gravel bed at the footing level, and the system is connected to a sump pit. Water seeping through the wall or floor-wall joint is captured and routed to the pump — which discharges it outside, safely away from your foundation.
This is the correct solution for 80–85% of GTA homes we inspect. Toronto and GTA clay-heavy soil is nearly impermeable — water doesn't drain through it, it accumulates around your foundation and pushes inward through micro-cracks and the floor-wall joint. Interior waterproofing works with your soil conditions rather than fighting them, at a fraction of the cost of exterior excavation and with no yard disruption.
$80-$120+ per Linear Foot
Most GTA homes: $5,000-$15,000
| Factor | Interior | Exterior |
|---|---|---|
| Cost | Lower | Higher |
| Disruption | Inside only | Yard/Driveway |
| Timeline | 1-2 Days | 3-7 Days |
| Best for | Most homes | Specific cases |
| Warranty | Lifetime | Lifetime |
What's Included in Our Interior System
Signs Your Basement Needs Interior Waterproofing
⚠ sign
Water seeping along the floor-wall joint
The classic indicator of hydrostatic pressure. Water exits at the lowest accessible point — exactly where interior drainage captures it.
⚠ sign
White chalky deposits (efflorescence) on walls
Mineral deposits left when water evaporates after passing through the wall. Active efflorescence means water is moving through your foundation now.
⚠ sign
Wet basement after rain or spring snowmelt
Seasonal wetness after major storms or snowmelt is the most common presentation in GTA homes on clay soil — water has nowhere to drain so it pushes in.
⚠ sign
Musty smell, mould, or mildew growth
Chronic moisture — even without visible water — creates mould conditions. A recurring musty smell means the moisture source hasn't been addressed.
✓ sign
Vertical or diagonal cracks in foundation walls
Shrinkage and settlement cracks become water entry points under hydrostatic pressure. Crack injection seals the crack; interior drainage relieves the pressure.
✓ Best Choice
Sump pump running constantly or failing
An overwhelmed pump usually means the drainage system feeding it is inadequate — interior waterproofing upgrades the full system, not just the pump.
How Interior Waterproofing Works
Comprehensive Site Assessment
Our experts evaluate your foundation, soil conditions, drainage patterns, and landscaping. We identify all water entry points and develop a custom waterproofing plan.
Comprehensive Site Assessment
Before digging, Canada Waterproofers calls Ontario One Call to have underground utilities marked, helping us excavate safely and avoid damaging vital services like gas, hydro, water, sewer, and telecom.
Foundation Excavation
We carefully excavate around your foundation down to the footing level. Landscaping, walkways, and structures are removed and cataloged for restoration if agreed upon.
Foundation Repair & Preparation
Foundation walls are cleaned and inspected. Any cracks are repaired with hydraulic cement. The surface is prepared for membrane application.
Waterproof Membrane & Drainage
A heavy-duty waterproof membrane is applied to the foundation walls. New weeping tile is installed at the footing, connected to a sump system or storm drain.
Backfill & Site Restoration
Foundation is backfilled with gravel and soil in layers. Proper grading is established, landscaping is restored, and final inspection is completed.
When to Choose Exterior Over Interior
⚠ Requires Exterior
Active foundation cracks with water intrusion above the floor
Horizontal cracks or cracks above the floor-wall joint can't be resolved by interior drainage alone — the wall face needs to be sealed from the outside.
⚠ Requires Exterior
Bowing, cracking, or inward wall movement
Signs of hydrostatic pressure causing structural movement. Exterior work is required to relieve lateral pressure on the wall and restore structural integrity.
⚠ Requires Exterior
Failed or deteriorated existing exterior membrane
Older homes with failed rubber or asphalt-based exterior membranes need the old material removed and a modern rubberized membrane installed over the clean wall.
⚠ Requires Exterior
Interior waterproofing not keeping up with water volume
If an existing interior system is overwhelmed despite properly sized sump pumps, the volume of inflow suggests the exterior membrane has failed and needs replacement.
✓ Best Choice
Pre-sale — buyer-requested permanent protection
Buyers and home inspectors increasingly request exterior waterproofing documentation at resale. An exterior-treated foundation eliminates one of the most common buyer objections in GTA real estate.
✓ Best Choice
Major renovation requiring complete foundation access
If you're excavating for a new addition, underpinning, or landscaping overhaul, adding exterior waterproofing at the same time reduces overall cost significantly.
Canada Waterproofers is here to help
No job is too big or too small. Get in touch with us!
Serving GTA, Kitchener-Waterloo, Hamilton & Niagara
Toronto
Etobicoke, North York, Scarborough, East York, Downtown, Beaches and all city neighborhoods
Mississauga
Port Credit, Streetsville, Erin Mills, Meadowvale, Cooksville & surrounding areas
Brampton
Bramalea, Heart Lake, Springdale, Sandringham, Credit Valley & surrounding areas.
Oakville
Glen Abbey, Bronte, Old Oakville, River Oaks, West Oak Trails & surrounding areas
Burlington
Alton, Millcroft, Brant Hills, Orchard, Palmer & surrounding areas
Hamilton
Ancaster, Dundas, Stoney Creek, Waterdown, Binbrook and surrounding areas
Milton
Coates, Harrison, Beaty, Clarke, Scott & Surrounding Halton Region areas|
St. Catharines
Lakeshore, North End, Port Weller, Port Dalhousie, Old Grenridge, Western Hill and surrounding areas
Interior Waterproofing FAQ
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