Crawlspaces & Basements.
What’s under your home tells a big part of its story. Crawlspaces and basements are where we catch moisture, structural, and pest issues early. Here’s what we check and how to keep them dry.
What we check during an inspection
Where it’s safely accessible, we get into these spaces — a lot of a home’s health shows up here first.
✓ Overall condition & access
We enter where access permits and note general condition.
✓ Moisture
Standing water, dampness, and efflorescence (white mineral staining) on masonry.
✓ Vapor barrier
Whether the crawlspace soil is covered and the barrier is intact.
✓ Structure
Joists, beams, posts, and the sill plate for rot, sagging, or damage.
✓ Sump pump
Presence and operation of a sump pump where one exists.
✓ Insulation, ventilation & pests
Condition of insulation and airflow, plus any signs of pests.
Common problems we find
✓ Water & dampness
Standing water or chronic humidity that threatens structure and air quality.
✓ Missing vapor barrier
Bare or exposed soil pumping moisture into the home.
✓ Rot & pest damage
Wood members compromised by moisture or wood-destroying insects.
✓ Sump pump failures
Pumps that are absent, failed, or improperly discharging.
✓ Poor ventilation
Stagnant, humid air leading to mold.
✓ Foundation seepage
Cracks and water entry along basement walls.
What you can maintain yourself
✓ Keep water away
Gutters and grading that direct water away from the home do most of the work.
✓ Test the sump pump
Pour a bucket of water into the pit and confirm it kicks on and drains.
✓ Maintain the vapor barrier
Keep crawlspace soil covered and patch tears.
✓ Control humidity
A dehumidifier in a damp basement makes a big difference.
✓ Check periodically
Look for water, pests, and rot a couple times a year.
✓ Protect the pipes
Insulate exposed pipes in these spaces against freezing.
Under Colorado homes
✓ Radon enters here first
The crawlspace or basement is where Colorado’s high-radon geology meets your living space. A sealed vapor barrier helps radon mitigation work; a bare-dirt crawl fights it.
✓ Snowmelt is the flood season
Our basements flood in March–June far more than in summer — deep snowpack plus warm spells plus spring rain. Test the sump before melt season, not after.
✓ Freezing crawlspaces
Vented crawlspaces at altitude freeze pipes and chill floors. Sealing and conditioning the crawl (with radon in mind) is often the better modern approach here.
✓ Critters winter over
Mice, voles, and the occasional raccoon treat foothills crawlspaces as winter housing. Shredded vapor barriers and tunneled insulation are the calling cards we find.
Common questions
How do I know if my sump pump works?
Lift the float or pour a bucket of water into the pit — it should kick on, evacuate the water, and shut off without rattling or short-cycling. Do it every spring before snowmelt. If the house depends on that pump, a battery backup is cheap insurance for the storm that knocks the power out at the exact wrong moment.
What is efflorescence and is it serious?
The white, chalky mineral bloom on concrete or block is left behind when water moves through masonry and evaporates. The powder itself is harmless; the message matters — water is passing through that wall. A little in an old basement is common; heavy or growing deposits mean improve drainage on that side.
Should a crawlspace have a vapor barrier?
Yes — 6-mil or heavier plastic over all exposed soil, seams overlapped and ideally taped, run up the walls a few inches. Bare soil pumps surprising amounts of moisture (and, in Colorado, radon) into the house. It’s one of the cheapest meaningful upgrades under a home, and we report its absence or damage every week.
Can I finish my basement after buying?
Address water first: any history of seepage, efflorescence, or a marginal sump becomes a mold problem once it’s behind drywall and carpet. On expansive Front Range soils there’s a second local rule — many basements here have floating floor slabs, and finishing work must accommodate slab movement. A basement that’s stayed dry through at least one full spring is the confidence test.
Why does my crawlspace smell?
Earthy or musty means moisture (check the vapor barrier and ventilation); sharp ammonia points at animals; sewage smell means a plumbing leak or a dried-out trap under there. Crawlspace air migrates upward into the living space — the “stack effect” — so a smelly crawl is a whole-house air-quality issue, not an out-of-sight one.
This guide is for general education. It reflects what we look for during a home inspection, not a substitute for a licensed professional. If you have a specific concern, please contact a foundation or waterproofing specialist — and of course, we’re always happy to take a look during an inspection.
More from our guides
Home Maintenance, Season by Season
A spring-through-winter checklist tuned for Front Range homes.
Read →Radon in Colorado
Why half of Colorado homes test high, county-by-county numbers, and what testing and mitigation really cost — with sources.
Read →Plumbing
Plumbing issues are some of the most common — and most expensive — problems we find. Here’s what we actually look at during an inspection, what tends to go wrong, and what you can stay ahead of yourself.
Read →Concerned about your crawlspaces & basements?
We’ll give your home a thorough, plain-English inspection and flag anything worth a closer look.