Crawl space checklist
A crawl space inspection checks six things in order: the outside of the house (grading, downspouts, vents), the access and safety conditions, the ground (standing water and vapor barrier), the framing (rot, sag, pests), the insulation, and the mechanicals (ducts, plumbing, wiring). Most homeowners can do the walk-through in 30 to 45 minutes twice a year. Anything wet, sagging, or smelling of sewage or gas is a stop-and-call finding.
What makes this one different
Before you go in
A crawl space is a confined space with wiring, water, and sometimes gas. The first six checks are done from the opening.
Six stop signs
If you see any of these, end the inspection and bring in the right professional:
The checklist
Tick each item as you go (your ticks are saved on this device), and photograph anything you mark. 'Note' means record it and decide what to monitor or fix; 'Stop & call' means the DIY inspection is over.
0 of 34 checked
Saved on this device only. Nothing is sent anywhere.
Walk the full perimeter before you open the access door.
| Done | Check | What to look for | Act when |
|---|---|---|---|
| Soil should fall away from the wall on every side | NoteLess than 6 in of drop in the first 10 ft, or soil sloping toward the wall | ||
| Extensions, splash blocks, or buried lines at every downspout | NoteAny downspout ending within 4 ft of the wall | ||
| Vents present, unblocked, above grade, screens intact | NoteVents buried by mulch or soil, or open vents on a crawl that is damp inside | ||
| Door closes, latches, is not rotted or chewed | NoteGaps a rodent could pass (about 1/2 in) | ||
| Stair-step or horizontal cracks, efflorescence, spalling brick | NoteAny crack wider than 1/4 in, or one you can see changing between visits | ||
| Siding, trim, or framing touching soil or mulch | NoteLess than 6 in of clearance between wood and soil |
Do this with a flashlight from the opening, before you crawl in.
| Done | Check | What to look for | Act when |
|---|---|---|---|
| Exposed wiring, open junction boxes, wires in water | Stop & callAny wiring touching water or hanging loose — do not enter | ||
| Sewage odor, rotten-egg gas smell | Stop & callAny — leave, ventilate, and call the utility or a plumber | ||
| Water across the floor | Stop & callDeeper than an inch or so, or reaching wiring or equipment | ||
| Fuzzy or dark growth across large areas of joists | Stop & callMore than about 10 sq ft — that is a professional remediation job | ||
| Snakes, wasps, animal nesting, active termite tubes | Stop & callLive animals or active insect colonies | ||
| Can you turn around and get back out? Is anyone at the top who knows you are in there? | Stop & callLess than about 18 in of clearance, or no one aware you are inside |
Cover the whole footprint, corners included; problems hide at the far end.
| Done | Check | What to look for | Act when |
|---|---|---|---|
| Puddles, dark damp soil, water lines on piers | NoteAny standing water more than a day after rain | ||
| Plastic over the soil, lapped at seams, up the piers | NoteBare soil, or plastic torn, displaced, or covering less than the full floor | ||
| Lift a corner: water beads or soil wet beneath | NoteWater pooling on or under the plastic | ||
| Construction scrap, old insulation, cardboard, wood on the ground | NoteAny cellulose debris (food for termites and fungus) | ||
| Pit with a pump, discharge line leaving the crawl | NotePump not running when the pit is full, or discharge ending inside the crawl | ||
| A $15 hygrometer left for a day | NoteAbove 60% RH sustained; above 70% is condensation territory |
Look up and along every joist line; press on wood with a screwdriver, don't stab it.
| Done | Check | What to look for | Act when |
|---|---|---|---|
| Dark staining, soft spots, fungal growth, sag | NoteScrewdriver sinks more than 1/4 in, or a visible sag | ||
| Pin meter on several joists if you have one | NoteAbove 19% — fungus grows above about 20% | ||
| Rot where the framing meets the foundation wall | NoteSoft wood anywhere along the perimeter | ||
| Leaning, rusted, or rotted posts; stacked blocks; crushed shims | NoteA post that moves by hand, or a gap between post and beam | ||
| Mud tubes on piers or walls, hollow-sounding wood, frass | Stop & callAny mud tube — call a pest inspector before anything else | ||
| Bounce or slope you noticed upstairs lines up with what you see here | NoteSlope over 1/2 in per 10 ft, or bounce over a specific beam line |
Check between the joists and along the walls.
| Done | Check | What to look for | Act when |
|---|---|---|---|
| Batts held tight to the subfloor, or foam board on the walls | NoteBatts fallen, sagging, or hanging from one side | ||
| Batts dark, heavy, compressed, or dripping | NoteAny wet insulation — it will not dry in place and holds water against the joists | ||
| Tunnels, nests, droppings in the batts | NoteAny nesting | ||
| Paper or foil facing toward the heated floor | NoteFacing down toward the crawl in a humid climate traps moisture |
Follow each run from where it enters to where it leaves.
| Done | Check | What to look for | Act when |
|---|---|---|---|
| Disconnected joints, crushed flex duct, sweating or dripping ducts | NoteAny open joint, or condensation dripping in summer | ||
| Drips, corrosion, wet soil under a line, sagging drain pipe | NoteAny active drip — a slow leak is the most common hidden moisture source | ||
| Rust, condensate line draining onto the soil | NoteCondensate discharging inside the crawl | ||
| Gas furnace or water heater in a crawl you plan to seal | NoteAny — sealing changes its combustion air; get it checked first | ||
| Chewed insulation, splices outside boxes, cable in contact with water | Stop & callAny chewed or submerged wiring | ||
| Vent terminates outside, not into the crawl | NoteLint or a disconnected vent in the crawl |
What to do with the results
One damp corner and a torn liner is a weekend job. Wet insulation plus soft joists plus standing water is a moisture system that has failed.
Fix the outside items first (grading, downspout extensions, vent clearance), replace or re-lap the vapor barrier where it is displaced, and leave the hygrometer in place. Re-check in six months.
What the humidity reading should beWater has a source: grading, a downspout, a plumbing drip, or groundwater. Find it before drying anything. Insulation that is wet will not recover in place.
Standing water in a crawl spaceThis is a structural and pest question first and a moisture question second. Get a pest inspection and a structural look before any encapsulation quote.
Rotted floor joistsPrefer answering questions to crawling? The should-you-encapsulate tool reads the same conditions from what you already know. And if the checklist turned up more than notes, a professional crawl space inspection is the next step; bring your photos and this list.
Related pages
Each zone above links to the guide that explains the fix.
The plastic-sheet test and a hygrometer reading, step by step.
Read moreWhy batts fall, why they are wet, and what replaces them.
Read moreThe inspection strip code requires when you encapsulate.
Read moreWhether the vents you counted meet code, and whether they should be open at all.
Read moreA neutral decision tool for what the findings point to.
Read moreIf the inspection turns into a quote, read it with this.
Read moreFAQs
Short answers for homeowners deciding whether to look, what to look for, and who to call.
Six zones in order: the outside of the house (grading, downspouts, vents, cracks), the safety conditions at the access, the ground (water, vapor barrier, debris, humidity), the framing and supports (rot, sag, termites, posts), the insulation (position and moisture), and the mechanicals (ducts, plumbing, wiring, dryer vent). Each item has a threshold that separates 'note it' from 'stop and call'.
Twice a year is a good rhythm: once in late spring before the humid season and once in fall after the leaves and rain. Add a look after any major storm, a plumbing problem upstairs, or if a floor starts to feel different. A hygrometer left in the crawl lets you check humidity between visits without crawling in.
Usually, yes, if the safety gate is clear: no wiring in water, no sewage or gas smell, enough headroom to turn around, and someone who knows you are in there. Wear a respirator, gloves, eye protection, and long sleeves; bring a bright flashlight and a screwdriver. If any stop sign shows up, end the inspection and bring in a professional.
Standing water or wet soil, a musty smell upstairs, insulation that has fallen or gone dark, soft or stained joists, a vapor barrier that is torn or missing, sweating ducts in summer, and humidity that stays above 60 percent. Any of these on their own is worth acting on; several together mean the crawl has been damp for a long time.
Many crawl space contractors inspect free because they hope to quote repairs, which is fine as long as you get more than one opinion. An independent home inspector or a structural engineer typically charges a few hundred dollars for a crawl-only visit, and that fee buys a report with no repair to sell. A DIY walk-through with this checklist costs a flashlight and an hour.
Roughly the same list, faster: access, standing water, vapor barrier, visible framing condition, insulation, ducts and plumbing, and evidence of pests. A general home inspector is not a structural engineer or a mold assessor, so their report will flag conditions and recommend specialists rather than diagnose. Reading the report against this checklist tells you which items are routine and which need a follow-up.
Sources