How much does foundation waterproofing cost?
The recorded membrane-only reference is $4–$7 per ft² of wall; exterior drain-only work is $30–$90 per ft. Water source, access, excavation and restoration determine the complete scope. Control runoff first when surface water is the cause; compare drainage and wall protection when water reaches the buried foundation.
Measure each scope separately before using the calculator.
Key facts as of Oct 30, 2026. Sources and recorded dates.
SIGNS
Which signs point to a foundation moisture problem?
Record where and when dampness appears: at a wall, at the floor edge or after rainfall. Photograph stains before covering them. A dry inspection day does not explain an intermittent leak.
- Water at a wall-floor joint or a recurring wet patch.
- White deposits, flaking masonry or damaged wall finishes.
- A crack with displacement or a wall that appears to move needs a structural assessment.
Guidance: University of Minnesota Extension: Moisture in basements, causes and solutions; PNNL Building America: Pre-retrofit assessment of crawlspaces and basements.
CAUSES
Why does water reach the foundation?
Roof runoff, ground sloping toward the house and ineffective buried drains can keep water against the wall. Moisture may also come from plumbing or humid air, so a damp room alone does not establish a need to excavate.
Guidance: PNNL Building America: Pre-retrofit assessment of crawlspaces and basements.
FIXES
What should a foundation waterproofing plan include?
Ask the inspector to identify the source, entry path and discharge destination. An exterior wall barrier and a drainage path do different jobs: the barrier limits entry while the drain carries water away. Confirm how the two connect.
For each offer, request measured wall area, drain length, excavation access, utility checks, backfill and finish restoration. Ask what inspection and maintenance the proposed system needs.
Guidance: PNNL Building America: Foundation wall water/damp-proofing; PNNL Building America: Pre-retrofit assessment of crawlspaces and basements.
Which costs belong in this scope?
| Work | Planning range |
|---|---|
| Exterior membrane only | $4–$7 / ft² of wall |
| Exterior foundation drain only | $30–$90 / ft |
Wall area means actual wall ft², not basement floor area. Drain and membrane installation may overlap; do not add these references into a complete project total without a confirmed scope.
Read the basement waterproofing cost guide for the worked example and price factors, or calculate an estimate for your measured scope.
Sources and dates
Public guidance checked Oct 30, 2026. Cost references retain the recorded Oct 24, 2026 retrieval date; this guide adds no new price observations.
- University of Minnesota Extension: Moisture in basements, causes and solutions
- PNNL Building America: Pre-retrofit assessment of crawlspaces and basements
- PNNL Building America: Foundation wall water/damp-proofing
- HomeGuide: basement waterproofing cost — recorded Oct 24, 2026.
Read how the calculator works and the source inventory for calculation limits.