Last updated: October 11, 2026.
There is no single price for waterproofing a basement. A sealed crack can cost a few hundred dollars, while a full exterior excavation can pass $20,000. The published estimates also disagree with each other, sometimes by a lot. This guide shows what two widely read cost guides report, explains why their numbers differ, and tells you what to check in a quote so you can compare contractors on the same terms.
Quick answer
Budget by the size of the problem, not by an average. Small, single fixes (one crack, one sump pump, sealant on a damp wall) are typically in the hundreds to low thousands of dollars. Whole-basement drainage systems and exterior excavation are typically in the tens of thousands. Both sources below report a top end of about $20,000 or more for full exterior work.
What the published guides report
We compared two guides: This Old House (updated March 2026, using data from Homewyse and Angi plus its own analysis of quotes) and Modernize (no update date shown). Figures are copied as the sources state them.
| Work | This Old House | Modernize |
|---|---|---|
| Interior drain tile / interior French drain | $60–$120 per linear foot (a separate section lists $25–$55) | $70–$100 per linear foot |
| Sump pump installation | $1,200–$2,500, professionally installed | $5,000–$16,000 (interior sump pump with installation) |
| Exterior French drain | $10–$100 per linear foot (French drains in general) | About $25 per linear foot, or $8,000–$15,000 for a full property |
| Exterior waterproofing / excavation | $7,000–$15,000 typical; full excavation with drains and membrane about $20,000 or more | Major excavation sometimes over $20,000 |
| Crack repair | Epoxy injection $800–$1,500 per crack | Not priced separately |
| Sealants and waterproof paint | Paint $1–$8 per sq ft; vapor barrier $1,500–$3,000 | Paint $2–$6 per sq ft; sealants $3–$7 per sq ft |
| Grading and landscaping | Not listed | $1,000–$7,000 |
For total project cost, This Old House estimates by basement size: about $6,260–$7,461 for 500 sq ft, $12,447–$14,833 for 1,000 sq ft, $18,634–$22,206 for 1,500 sq ft and $24,817–$29,575 for 2,000 sq ft. Modernize instead reports a typical total of $1,500–$7,000 with a national average around $5,000, and a full range of $500 to over $20,000.
Why the numbers do not agree
We did not average the two sources, because they are not measuring the same thing. The differences most likely come from scope and definitions:
- What is being priced. A pump-only job and a complete interior drainage system with a pump are very different projects, yet both are often called “sump pump installation.”
- Whole basement or one problem. Size-based totals assume treating the whole basement. “Typical” totals across all jobs include many small repairs.
- Data source and date. One guide states where its data comes from and when it was updated. The other does not.
- Inconsistency inside a single guide. Even one source gives two different ranges for interior drain tile in different sections.
The practical conclusion: treat these figures as planning ranges, not quotes, and use them to spot a bid that looks far outside the range for the scope described.
What drives the price of your job
- Foundation type and condition. Block walls and older homes can cost more, and may need structural work first.
- Basement size and depth, which sets how many linear feet of drain or wall must be treated.
- Interior versus exterior work. Exterior work means excavation and is usually the most expensive. See interior vs. exterior waterproofing.
- Your location, including labor rates, soil, permits and flood risk.
- How severe the water damage is, including tearing out finished walls and floors.
Costs people forget
- Permits and inspections: from $75 to $500 according to This Old House, and up to $500 according to Modernize.
- Gutters and downspouts: This Old House lists $650–$1,750 for gutter work, which can matter if roof water is part of the problem.
- Mold removal: $500–$3,500 per This Old House but often $4,000 or more per Modernize, another example of how much these estimates vary.
- Water damage repair: This Old House reports $1,360–$6,290.
Try the lower-cost fixes first
The U.S. Environmental Protection Agency advises fixing water that enters from outside, with options that range from simple landscaping to major excavation and waterproofing, and says the ground should slope away from the foundation. It also notes that missing gutters or water flowing toward the house can cause basement water problems (EPA). Extending downspouts and correcting grading cost far less than a drainage system, so rule them out before accepting a large bid. Our exterior drainage guide covers these surface fixes.
What a written quote should spell out
- Whether the work is interior or exterior, and the linear feet of drain or wall covered.
- The sump pump model, whether a battery backup is included, and where the water discharges.
- Permits, cleanup, and any restoration work, and who is responsible for each.
- The warranty terms and whether it transfers if you sell the house.
- The payment schedule. Be cautious about large deposits before work starts.
Get at least three written quotes for the same scope. Our guide on hiring a waterproofing contractor covers the questions to ask and the red flags to watch for.
Your right to cancel a contract signed at home
The Federal Trade Commission’s Cooling-Off Rule requires sellers who make certain sales at your home or other non-business locations to tell you that you can cancel within three business days. The rule applies above a minimum purchase amount and has exceptions, and many states add their own protections. Check the rule text (16 CFR Part 429) and your state attorney general’s office before relying on it for a specific contract.
Related guides
How we put this guide together
We read the two cost guides cited above and the EPA and FTC pages on October 11, 2026, and reported their figures as written, with the source named next to each number. We did not average sources or estimate regional prices, because we do not have verified regional data. When we have a better source, we will update this page and note the date.
Sources
- This Old House, “How Much Does Basement Waterproofing Cost? (2026 Pricing),” updated March 4, 2026.
- Modernize, “How Much Does Basement Waterproofing Cost?” (no update date shown).
- U.S. EPA, “What are the main ways to control moisture in your home?”
- U.S. Federal Trade Commission, Cooling-Off Period for Sales Made at Home or Other Locations
Want to see the published ranges added up for your own measurements? Try our basement waterproofing cost calculator.
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