Wet Basement: Causes and How to Fix It
Water in the basement has a handful of causes, and some are cheap to fix. Here is how to tell which one you have.
Common causes of a wet basement
- Surface water: gutters overflowing, downspouts dumping near the wall, or soil sloping toward the house. The most common and cheapest to fix.
- Groundwater and hydrostatic pressure: water pushing through the wall-floor joint or cracks after heavy rain or snowmelt.
- Foundation cracks and pipe penetrations.
- Condensation: humid air on cool walls, especially in summer. Looks like a leak but needs a dehumidifier, not waterproofing.
- Plumbing leaks from supply lines, water heaters or washers.
Leak or condensation? A simple test
Tape a square of plastic or foil tightly to the damp wall for a couple of days. Moisture on the room side points to condensation; moisture behind it (wall side) points to water coming through the wall.
What to do now
- Remove standing water and dry the area quickly. EPA advises drying wet materials within 24 to 48 hours to prevent mold growth.1
- Check gutters and downspouts; extend downspouts away from the foundation.
- Run a dehumidifier.
- If water keeps coming in, get a waterproofing assessment before you finish the space.
Common questions
Why is my basement wet after it rains?
Usually surface water: overflowing gutters, short downspouts, or soil sloping toward the house. Persistent seepage after rain can also mean groundwater pressure at the wall-floor joint.
Is a damp basement a problem?
Ongoing moisture can lead to mold and damage finishes. Find and fix the source; EPA advises drying wet materials within 24 to 48 hours.
Can I finish a basement that gets wet?
Fix the water problem first. Finishing over moisture traps it behind walls and floors.
General information summarized from the public sources listed below. It isn't professional, medical or legal advice. A licensed professional who inspects your home can tell you what it needs.