Start with what you know about the house
These questions help a contractor understand the crawlspace before anyone crawls into it.
- Is the crawlspace under the original house, an addition, or both?
- Is the floor bare soil, covered with plastic, or concrete?
- Are there foundation vents to the outside, and are they open or closed?
- Do ducts, plumbing or a furnace run through the crawlspace?
- Has anyone seen standing water down there after storms or irrigation?
Why crawlspaces stay damp
Bare soil gives off moisture continuously, even in a dry climate. If the vapor barrier over the soil is torn, missing or bunched up, that moisture rises into the crawlspace air and onto cold joists and subfloor. Foundation vents were long recommended to dry crawlspaces, but in summer they can let warm, humid outside air in to condense on cooler surfaces, and in winter they make pipes and floors cold.
In a home where a crawlspace addition joins an older full basement, water can also move between the two. A crawlspace that slopes toward the basement wall may channel water there during heavy rain or long irrigation cycles.
What to look for, from the access hatch if possible
- White or dark fuzzy growth on joists and the underside of the subfloor
- Torn, missing or water-filled plastic over the soil
- Duct insulation that is sagging, wet or disconnected
- Wood that looks dark and feels soft when gently pressed with a screwdriver
- A musty smell in rooms directly above, especially closets
- Signs of past rodent activity, which can complicate cleanup
Two common correction strategies
Vented crawlspace, improved
- Replace and seal the ground vapor barrier
- Correct exterior grading and downspouts
- Insulate the floor above and protect pipes
- Lower upfront complexity
Closed or conditioned crawlspace
- Seal vents and install a heavier, sealed ground liner up the walls
- Insulate foundation walls instead of the floor
- Provide conditioning or dehumidification as designed
- Check local code requirements with the building department
Common questions
- Can mold in the crawlspace affect air in the house?
- Air moves upward from crawlspaces into living areas through gaps in the floor, around pipes and through duct leaks, so odors and spores can reach rooms above. That is a good reason to address it rather than ignore it.
General information for Cherry Hills Village, not a quote or professional advice. In an emergency, call 911.