Basement waterproofing

Basement waterproofing in Durham Region

Waterproofing covers everything from sealing one crack to digging around the whole house. The right choice depends on where the water gets in, how your foundation is built and whether the basement is finished. Here's how the options compare.

Get matched with a contractor How it works

Free for homeowners. We match you with a vetted, independent local contractor. See how it works.

Four levels of waterproofing

Start at the top. Many wet basements are fixed at the first or second level, for a fraction of the cost of a full system.

Level	What it involves	Typical cost (CAD, 2026)
1. Outside basics	Clean gutters, extend downspouts 1.5–2 m out, slope soil away from the house, fix window wells	Often DIY, or a few hundred dollars
2. Targeted repairs	Crack injection, sealing tie-rod holes, sealing pipe entries	$500 – $1,500 per crack, $75 – $150 per tie rod
3. Interior drainage	New weeping tile inside the footing, a membrane on the walls, draining to a sump pump	$3,500 – $15,000
4. Exterior waterproofing	Dig to the footing, repair and membrane the wall, new weeping tile, backfill with clear stone	$5,000 – $12,000 per wall; $15,000 – $35,000 whole house

Interior vs exterior waterproofing

	Interior drainage	Exterior waterproofing
How it works	Water reaches the wall, then runs down behind a membrane into new weeping tile inside the footing and out through a sump pump	The wall is sealed from outside, so water never reaches the concrete. New weeping tile carries it away
Disruption	Inside: the basement floor is cut along the walls, and finished walls come down	Outside: a trench down to the footing. Landscaping, decks and walkways may come up
Best for	Tight lots, shared driveways, failed clay weeping tile, high water tables, year-round work	Block walls, homes with a finished basement you don't want to open, recurring leaks through the walls
Needs	A reliable sump pump, ideally with battery backup	Utility locates through Ontario One Call before digging
Cost per linear foot	About $70 – $150	About $150 – $300

Ranges from published Toronto-area price guides, 2026. They're general estimates, not quotes.

Damp-proofing isn't waterproofing

Many Durham homes, especially those built before the 1990s, have only a black, tar-like damp-proofing coat on the outside of the foundation. It slows moisture but doesn't hold back water under pressure, and it gets brittle with age. Newer homes often add a dimpled plastic drainage membrane. Knowing which your house has helps explain why it leaks.

How to read a waterproofing quote

A good quote spells out exactly what's included. Compare quotes line by line on:

The walls and linear feet covered, and how deep they'll dig or cut
The membrane and drainage products, by name
Whether weeping tile is replaced, and where it drains (sump or storm connection)
Backfill material, restoration of landscaping and walkways, and drywall removal and replacement inside
The warranty in writing: length, what's covered, and whether it transfers if you sell
Proof of liability insurance and WSIB coverage

Red flags: pressure to sign the same day, a price that drops sharply when you hesitate, cash only, a vague "lifetime warranty" with no written terms, or a whole-house exterior job pitched when you've shown them one leaking crack.

Sump pumps and backwater valves

A sump pump ($1,000 – $3,000 installed) removes groundwater collected by weeping tile. It's the heart of an interior drainage system, and a battery backup keeps it running in a power outage. A backwater valve ($2,000 – $4,500) is a plumbing device that stops sewage flowing back into the house through floor drains. It's installed by a licensed plumber, not a waterproofing contractor.

Waterproofing across Durham Region

Durham's lakeshore towns sit mostly on clay-rich glacial till, with sandier ground and higher groundwater near the lake and creek valleys. Which fix makes sense varies from town to town and from street to street:

Oshawa: century-old block foundations downtown and new builds in the north
Whitby and Brooklin: stone foundations downtown, newer poured walls up north
Pickering: high water near Frenchman's Bay, plus brand-new Seaton
Ajax: post-war homes with ageing weeping tile, plus the 1970s–80s subdivisions
Bowmanville, Courtice and Newcastle: old town cores, new subdivisions and rural homes on wells

Full price list: Durham foundation and waterproofing cost guide.

Get matched with a contractor

Common questions

Is interior or exterior waterproofing better?

Exterior waterproofing stops water at the wall before it reaches the concrete, and it's the most complete fix, especially for block foundations. Interior drainage lets water reach the wall, then catches it and pumps it out. It costs less, can be done any time of year, and avoids digging up driveways, decks and gardens. Both work when they're done properly. The right one depends on your house, and a good contractor will explain their reasoning.

How long does basement waterproofing take?

Crack injection takes a few hours. An interior drainage system or an exterior job on one or two walls usually takes a few days, and a whole-house exterior job can take a week or more depending on access, depth and weather.

Can waterproofing be done in winter?

Interior work, meaning crack injection and interior drainage, can be done year-round. Exterior excavation is possible in winter but harder and slower in frozen ground, so most exterior jobs in Durham are done between spring and late fall.

Do I need a permit for basement waterproofing?

Crack injection and most waterproofing don't need a building permit. Structural repairs, underpinning and changes to the foundation usually do, and installing a backwater valve usually needs a plumbing permit. Check with your town's building department or ask the contractor.

Will waterproofing stop sewer backups?

No. Sewer backups come up through floor drains from the sanitary sewer. A backwater valve, installed by a licensed plumber, is what prevents them. Waterproofing deals with groundwater coming through or under the foundation walls.

Tell us what you're seeing

Free, no obligation. We'll review your request and get back to you, then put you in touch with a vetted local foundation contractor who'll book an assessment and give you a written quote.