Planning estimate · Q3 2026 pricing
Basement waterproofing
Waterproofing is priced by the length of foundation wall treated and by method. Interior drainage manages water that reaches the wall; exterior excavation keeps it off the wall. Price the water before you price finishing.
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Hidden costs on waterproofing projects
These are included as allowances in the estimate above. Check that any contractor quote covers them too.
- Landscaping, patios, and driveway reinstatement after excavation
- Finished walls and flooring removed to reach the perimeter
- Structural crack or footing repair found once the wall is exposed
- Electrical circuit for the sump pump and its battery backup
- Plumbing permit for a backwater valve
- Downspout, grading, and window well fixes that should come first
Questions homeowners ask
- Is interior or exterior waterproofing better?
- They do different jobs. Interior drainage collects water that reaches the wall and pumps it out, so it depends on the sump. Exterior work keeps water off the wall but means excavating to the footing, which is why it costs roughly twice as much per foot in this calculator.
- Do I need a permit to waterproof a basement?
- Installing a new sump pit and pump or a backwater valve normally needs a plumbing permit, and structural foundation repair needs a building permit. Ottawa, for example, charges $117 for a plumbing-only permit in 2026, and fees vary by city. Replacing a pump in an existing pit usually does not. Check your city's requirements and fee before work starts.
- Should I fix grading and downspouts first?
- Yes. Downspouts that discharge against the wall and soil that slopes toward the house wet a lot of basements. Those fixes cost far less than a drainage system, and they are worth trying through a spring thaw before you commit.
Typical schedule: 2 to 5 days for interior work, 1 to 3 weeks for exterior excavation. See the full renovation timeline.