Signs Something Is Leaking Under Your House

Crawl spaces are good at hiding leaks. The pipes run in the dark, insulation wraps them, and the soil underneath soaks up a lot of water before anything shows. In Boise, where so many houses from the Bench to the North End sit over one, the signs usually show up indirectly.

Smell comes first

An earthy or musty smell that's new, or stronger than usual, is often the earliest clue. It tends to be strongest near floor registers and closets on outside walls. A sewage smell is different and points to a drain line, which needs a plumber either way.

Floors that feel wrong

Cool, damp-feeling floors near a bathroom or kitchen. Vinyl lifting at a seam. Hardwood cupping in one area. A soft spot that wasn't there last year.

Air and bugs

Higher indoor humidity, condensation on windows in rooms that didn't fog before, and more gnats or mosquitoes can all come from a wet crawl space.

The bill and the meter

A bill that rises and stays up, with no change in how you use water, is worth a meter check. How to check. If the meter moves with everything off and stops when you close the house shutoff, the leak is inside, and on a crawl-space house that often means under the floor.

Seasonal patterns that fool people

Boise's irrigation season soaks yards from spring through fall. Sprinkler heads aimed at the foundation, or a downspout emptying beside a vent, can put water into a crawl space without any plumbing leak at all. If the dampness shows up during irrigation season and the meter test is clean, look outside first.

The opposite pattern is a cold snap in winter followed by dampness in spring: that's classic freeze damage. Pipes leaking after a freeze.

Looking for yourself, safely

If you can open the hatch and see in, a flashlight look is reasonable. Look for: water on the vapor barrier, insulation hanging down or dark, pipes with white crust or green staining at joints, and wet soil in one area. Don't go in if there's standing water near wiring, if you smell gas or sewage, or if the space is too tight to move in. Shut off the water first if anything is spraying.

What a technician does differently

Moisture meters, a thermal camera, pressure tests by section, and the experience to know where lines usually run in houses of a given age. Crawl space leak detection.

After the leak is fixed

Wet insulation and vapor barrier usually need to dry or be replaced. That's water damage work, often a different company.