Basement Waterproofing · Materials and methods · Updated November 2026
Interior vs. Exterior Basement Waterproofing
Exterior waterproofing stops water at the outside of the foundation wall. Interior waterproofing collects water that gets through and pumps it away. Both work; which fits depends on access, budget and where the water comes from.
Side by side
| Interior | Exterior | |
|---|---|---|
| How it works | Drain tile inside the perimeter, under the slab edge, to a sump pump | Excavate outside, apply membrane to walls, add footing drain |
| Typical cost drivers | Interior drain $60–$120 per linear ft.; sump pump $1,200–$2,500 | Exterior drain $10–$100 per linear ft.; excavation $50–$200 per cubic yard |
| Disruption | Inside the basement; finished walls may need to come out | Yard, landscaping, walkways and decks near the house |
| Stops water reaching the wall? | No; manages it | Yes |
| Good for | Most basements; homes with limited outside access | New construction, major leaks, or when the outside is accessible |
From our basement waterproofing cost guide.
Start with the cheaper fixes
Before either system, fix gutters, downspouts and grading. Fixing grading and downspouts typically costs $700–$5,000 and solves many problems. See water in the basement after rain.
Other options
- Epoxy injection for a single leaking crack: $800–$1,500 per crack.
- Interior sealers ($1–$9 per sq. ft.) help with minor dampness, not water under pressure.
- Dehumidifiers ($800–$2,000 installed) address humidity, not leaks.
Questions to ask
- Where is the water coming in, and why do you think so?
- Will finished walls or flooring need to be removed?
- What warranty comes with the system, and is it transferable?
- Is a battery backup included for the sump pump?
Cost figures are national ranges from the sources listed in our basement waterproofing cost guide, not a quote from FixFinch or any contractor.