Crawl Space Waterproofing & Encapsulation

Crawl spaces collect groundwater and humid outside air. That moisture leads to musty smells, sagging insulation and damp wood framing.

Waterproofing a crawl space usually combines drainage to remove standing water with a sealed vapor barrier on the floor and walls.

A local contractor can inspect your crawl space and recommend what it needs.

What encapsulation includes

• A heavy plastic vapor barrier on the floor, often run up the walls and sealed at the seams.
• Drainage and a sump pump if water stands in the crawl space.
• Sealing vents and the rim joist to keep humid outside air out.
• Often a dehumidifier to control humidity year-round.

Typical costs

This Old House puts crawl space encapsulation at about $5,500 on average, with a range of $1,500 to $15,000, or $3 to $7 per square foot.

Signs your crawl space has a moisture problem

• Standing water or wet soil after rain.
• Musty smells in the rooms above.
• Sagging or damp insulation between the floor joists.
• Condensation, mold or dark staining on wood framing.
• Cold floors and higher humidity in the house.