Moisture in the Crawl Space

Moisture under a house is quiet until the floor smells or the insulation sags. Crawl spaces take water from the ground, from rain pushed against the foundation, and from ducts or pipes that sweat or leak. You do not need a gadget to notice a wet one. You need a safe look and an honest walk outside.

Outside first, because it is safer. During or after rain, where does roof water go? Downspouts should carry it away, not dump it at the wall. Gutters that overflow are doing the same thing from higher up. Soil and mulch should not bury the siding. A hole beside the foundation that holds water will share with the space under the floor. Fixing those is sometimes a Saturday and sometimes a landscaper. Either way it is the right category. Dehumidifiers and sprays are the wrong category if the yard is pouring in.

At the hatch, flashlight, feet on solid ground, no crawling through muck. Look for standing water, a dirt floor that is dark and damp, insulation that is wet or fallen, ducts with water on them, pipes that drip. A small plumbing drip is a plumber. Wet ducts are an HVAC conversation. A pond after every storm is drainage. Take pictures and get out. If you cannot enter safely, the pictures stop at the door and you call someone who does this work.

What not to do: do not lay plastic down over standing water and call it a vapor barrier. A cover on a pond is a cover on a pond. Do not close every vent because a video said all crawl spaces should be sealed. Some houses are built to vent that space, some are built to close it, and the wrong choice for this house can make moisture worse. Ask a local person who will look, not a general rule from another climate. Do not run a fan that blows crawl air into the living room to "dry it." You moved the smell.

Wood that is soft or visibly decayed is a structural question for a pro, not a smell question for a spray. Say what you see. Soft rim board is a different sentence from damp dirt.

The rooms above get a gauge. If they are humid and musty and the hatch matches, the floor is part of the house's air. Filter changes will not dry soil. They still matter for dust. They are not the crawl space plan.

Write three things: where rain goes, what the hatch shows, whether ducts or pipes are wet. That is enough to hire well.

One rainy afternoon outside is worth more than a bag of moisture absorber under the floor. Walk the downspouts while they are working. A spout that splashes the wall is a find you can point at. A spout that runs out to the yard is one less theory. You are building a short list, not a science project.

If a contractor wants to sell a full encapsulation on the first call, ask them what they saw about the gutters and the grading. A sealed space with water still running in is a bucket with a lid. You can say you want the outside water handled in the same plan. That is a reasonable sentence.

Keep kids and pets out of an open hatch. The smell is not an invitation. Close it when you are done looking, and do not store the winter clothes in a bay you just decided is damp. Fabric in a wet crawl space becomes the next smell you carry upstairs.

If someone in the house is getting worse, that is a doctor conversation, and opening walls or the furnace cabinet is a job for a licensed pro.

Crawl space moisture is pictured without the folklore in When Your House Doesn't Feel Right. It is $2.99 at https://clearnestair.com/book.