Wet basementCauses, fixes and what each fix costs
Most wet basements are caused by water outside the house: overflowing gutters, short downspouts, or soil sloping toward the foundation. Gutter cleaning costs $200 to $400 a visit and regrading soil costs $500 to $3,000, according to Fixr.com. If water keeps coming in after that, an interior perimeter drain runs $40 to $120 per linear foot, plus $600 to $2,500 for a sump pump.
Why is my basement wet?
- Gutters and downspouts that overflow or empty right next to the foundation.
- Grading: soil that slopes toward the house instead of away from it.
- Hydrostatic pressure: groundwater pushing up through the floor or the joint where the floor meets the wall, often after heavy rain.
- Cracks in the foundation walls or floor.
- Condensation: humid air hitting cool walls, which looks like a leak but isn't one.
- Plumbing leaks from pipes, water heaters or washing machines.
How do I tell condensation from a leak?
Tape a square of plastic wrap or foil to the damp wall, sealed on all sides, and leave it for a day or two. If moisture forms on the room side, it is condensation from humid air, and a dehumidifier is the fix. If moisture forms behind it, water is coming through the wall.
What should I check first?
- Watch the gutters in a heavy rain. Do they overflow?
- Check where each downspout empties. It should discharge well away from the foundation.
- Look at the soil along the house. It should slope away, not toward it.
- Note where the water shows up: one crack, along the bottom of the walls, or up through the floor.
- Check for plumbing leaks near the wet spot.
What does each fix cost?
| Fix | Typical cost | Source |
|---|---|---|
| Gutter and downspout cleaning | $200–$400 per visit | Fixr.com |
| Downspout extension (part) | $2–$17 each | Fixr.com |
| Regrading soil around the house | $500–$3,000 | Fixr.com |
| Dehumidifier, installed | $1,000–$2,800 | Fixr.com |
| Epoxy crack injection (per crack) | $250–$1,000 (Fixr.com); $800–$1,500 (This Old House) | Fixr.com; This Old House |
| Interior waterproofing (drain, sump pump, coatings) | $2,000–$6,000 | This Old House |
| Exterior waterproofing | $7,000–$15,000 | This Old House |
Full breakdown: basement waterproofing cost.
When do I need a waterproofing contractor?
Call a contractor if water keeps coming in after the gutters, downspouts and grading are fixed, if water comes up through the floor, if a wall is cracked wider than a hairline, bowing or leaning, or if the basement floods. Bowing or leaning walls are a structural problem, not just a water problem. Get at least three written quotes.
Is a wet basement dangerous?
Ongoing dampness can lead to mold and wood rot and can damage anything stored in the basement. Standing water near electrical outlets, panels or appliances is a shock risk. Stay out of a flooded basement until the power to it is shut off.
Common questions
Why is my basement wet after it rains?
Usually because rainwater collects next to the foundation, from overflowing gutters, short downspouts or soil that slopes toward the house. Fix those first.
How much does it cost to fix a wet basement?
From $200 to $400 for a gutter and downspout cleaning (Fixr.com) to $2,000 to $6,000 for interior waterproofing (This Old House). Exterior waterproofing costs more, at $7,000 to $15,000 (This Old House).
Will a dehumidifier fix a wet basement?
Only if the problem is condensation or general humidity. It does not stop water leaking through walls or the floor.
Can a wet basement cause mold?
Yes. Mold grows where moisture stays for days at a time. Drying the space and fixing the source of the water matter more than cleaning the mold alone.
Sources
- Fixr.com, Basement Waterproofing Cost (page updated Feb 6, 2026) — fixr.com, checked Nov 3, 2026
- Fixr.com, Downspout Installation Cost, extension line (page updated Jan 31, 2025) — fixr.com, checked Nov 3, 2026
- This Old House, Basement Waterproofing Cost (page updated Mar 4, 2026) — thisoldhouse.com, checked Nov 3, 2026
8 questions to ask any basement or foundation contractor
Ask these before you sign, whoever you hire.