InspectCamAround the house
How to check your crawl space for moisture, mold and pests
By , developer of InspectCam · Published · Last updated
Start at the access opening. With a light that stays on and your phone's camera, you can check most of what matters without crawling in: standing water, wet or fallen insulation, mold on the joists, gaps in the plastic on the ground, termite mud tubes and leaking pipes. Record a short video so you can look again or send it to someone. If you see standing water, sewage or damaged wiring, leave it to a professional.
Most people never look in their crawl space. It's dark, it's tight, and nobody wants to lie on the ground under the house to find out whether anything is wrong. So problems that start small, a slow drip or a torn sheet of plastic, get months to grow.
You don't have to crawl in to find out. Most of the warning signs are visible from the opening if you can get light and a camera in there together. This guide covers where to look, what each sign means, and how to check it with your phone.
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Start at the access opening
Every crawl space has a way in: a hatch in the floor, often in a closet, or a small door in the foundation wall outside. The building code sets the minimum size, and it isn't generous. IRC section R408.4 asks for at least 18 by 24 inches through a floor and 16 by 24 inches through a wall.
That opening is the right place to start even for professionals. InterNACHI's standards of practice, which many home inspectors work to, say an inspector is not required to enter a crawl space that isn't readily accessible, "or where entry could cause damage or pose a hazard to the inspector". Looking from the opening first tells you whether going in is necessary at all.
What to look for
These are the signs InterNACHI's guides tell inspectors to check in a crawl space, and what each one usually points to. Moisture sits behind most of them, which is why the EPA puts it bluntly: "The key to mold control is moisture control."
| What you see | What it can mean |
|---|---|
| Standing water or wet soil | Water is getting in. The next job is finding the source. |
| Plastic on the ground with gaps, tears or missing sections | Ground moisture can get in through the gaps. Sheeting only works if it's continuous, and in a sealed crawl space the building code requires it over all the exposed earth. |
| Insulation that is wet, sagging or has fallen | Wet insulation loses much of its value, and wet conditions encourage mold and wood rot. |
| Water drops on pipes, ducts or wood | Condensation: damp air meeting cooler surfaces. |
| Dark staining or growth on joists and the subfloor | Mold or mildew. |
| Soft, crumbling or darkened wood | Wood rot, which can need structural repair. |
| Drips or wet patches under pipes and drains | A leaking drain or supply line. |
| Mud tubes on walls or piers | Termites. |
| Droppings or carcasses | Animals or pests have been living there. |
| Loose or fallen wiring, open junction boxes | An electrical hazard. Don't touch it. |
Sources: InterNACHI's vented crawlspace guide, vapor retarder inspection, crawlspace hazards and under-floor crawl space pages.
Standing water is the one not to leave. The EPA's advice is to dry water-damaged areas and items within 24 to 48 hours to prevent mold growth. Water sitting under a house for weeks is the opposite of that.
How to check it with your phone
The obstacle is light. A flashlight in one hand and a phone in the other is awkward through a small opening, and many people find their flashlight goes off when they open the camera. InspectCam, which I build, opens with the rear camera live and the light already on, so one hand does both.
- Open the app at the opening. The light is already on. Put the phone through the hatch and pan slowly across the space.
- Look closer at anything odd. Pinch or tap a zoom button to get close to a joist, a pipe joint or a patch of ground, then tap it to focus. On phones whose camera offers it, the 0.6× button shows more of the space at once.
- Record a short video as you pan. The light stays on while you record. You can then watch it properly in daylight, or send it to a plumber, a pest company or whoever you need.
- Take photos of anything worth showing. The light stays on through the photo too, with no flash; we've checked that on a Pixel 6a with the current release.
If you switch away to send the video and come back, the light comes back on with the camera.
Be realistic about what the opening shows you. A phone at the hatch sees what's in line of sight. The far side of the space, and anything behind piers or ducts, needs someone to go in.
When to call a professional
Some of what you find is a weekend job: a pipe joint you can reach, a sheet of plastic that has slipped. Some isn't. InterNACHI's own guidance sends surface mold or fungal growth to a certified mold inspector, and wood rot can mean structural repairs to the framing.
If what you see includes standing water or sewage, loose wiring, anything that looks structurally unsound or signs of animals, don't go in yourself. InterNACHI tells its own inspectors never to enter a crawl space without protective equipment, and to make sure someone knows they're in there. The video you took from the opening is exactly what a contractor will want to see before quoting.
The same method works at the attic hatch
An attic is the same problem upside down: dark, tight, and reached through a small opening, usually from the top of a ladder with one hand free. Put the phone through the hatch, look around on the screen, and record a short video to show someone. If your phone gets very hot, Android may switch the light off to protect it. That's a safeguard, not a fault.
Questions people ask
How do I check my crawl space without going in?
Open the access hatch or the door in the foundation wall, and look in with a light that stays on. With your phone's camera held through the opening you can zoom in on joists, pipes and the ground covering, and record a short video to look at properly afterwards or send to someone. You won't see every corner from the opening, but you'll see enough to know whether anything needs a closer look.
What should a crawl space look like?
Dry. Where the ground is covered with plastic sheeting, it should have no gaps or tears; the wood framing should be dry and firm, insulation should be in place rather than hanging down, and there should be no standing water, no droppings and no mud tubes on the walls.
What does a bad crawl space look like?
Standing water or wet soil, torn or missing plastic on the ground, insulation that is wet or has fallen, dark staining or growth on the joists, soft or crumbling wood, water drops on pipes and framing, leaking drains, droppings, termite mud tubes, and loose or fallen wiring.
How do I check my crawl space for mold?
Look at the undersides of the floor framing and the subfloor for dark staining or growth, and check whether the insulation or the ground is wet. Mold follows moisture, so find where the water is coming from. InterNACHI, the home inspectors' association, says surface mold or fungal growth calls for a certified mold inspector.
Is it safe to go in a crawl space?
It can be hazardous. InterNACHI lists mold, pests, standing water or sewage, asbestos insulation, improper wiring and structural collapse among crawl space hazards, and tells its own inspectors never to enter without protective equipment and to make sure someone knows they are in there. Its standards also say an inspector is not required to enter a crawl space where entry could pose a hazard.
This page is a guide to what's visible, not a substitute for an inspection. If something here doesn't match what you found, tell us.