Start from the symptom

What are you seeing?

You do not need to know the name of the fix. Find the thing you have noticed below. Each entry says what it usually points to and which page explains the repair.

Call (205) 555-0115

Crawl space

Signs from under the floor

A musty smell indoors, worse in summer

Air from under the house rises into the rooms above. When the crawl space is humid, the smell comes with it. It is usually strongest near floor registers and in closets on outside walls.

Read next: Encapsulation · Dehumidifiers

Floors that feel soft, springy or uneven

Wood that stays damp loses stiffness. A joist or a patch of subfloor may be giving way, or a support may have shifted. It needs someone to look from below with a moisture meter.

Insulation hanging down or lying on the dirt

Fiberglass soaks up moisture from humid air, grows heavy and pulls loose. It is a sign of the air, not a fault in the insulation.

Read next: Crawl space repair · Encapsulation

Puddles or mud under the house after rain

Liquid water is getting past the wall or under the footing. Look outside first for a downspout or a slope aimed at that side of the house.

Read next: Yard drainage · Sump pumps · Crawl space repair

Ducts and pipes dripping

Cold metal in warm, wet air collects condensation. A few drops are normal on the most humid days. Steady dripping, rust streaks or wet soil beneath the ducts mean the air under the house is too damp.

Read next: Dehumidifiers · Encapsulation

Dark stains or fuzzy growth on joists

Mold needs moisture. On framing it shows that the wood has been damp for a good while. Cleaning it without drying the space only resets the clock.

Signs in a basement

Water on the floor along a wall after heavy rain

The soil outside has filled with water and it is coming in at the joint between wall and floor. Note which wall, and how long after the rain it appears.

Read next: Basement waterproofing · Wet basement

White powder or a chalky crust on the wall

Water moving through masonry carries mineral salts and leaves them on the surface as it dries. The powder is harmless. The moisture behind it is the thing to deal with.

Read next: Wet basement · Exterior waterproofing

A wet streak below a crack, a pipe or a window

Water is entering at one identifiable point. That is often a small repair, provided the source is confirmed first.

Damp walls and a clammy feel with no visible water

It may be condensation on cool masonry or moisture seeping through it. A taped square of plastic on the wall tells you which.

A sump pump that never stops, or never starts

A pump that runs constantly may have a stuck switch or a failed check valve. One that stays silent while the pit fills has lost power or failed.

Water pooling against the house outside

Ground that tilts toward the wall, or a downspout that stops short, feeds everything listed above. It is also the simplest cause to remove.

Things that look similar but are not waterproofing

A room flooded right now. Pumping out and drying is a water damage company's work. Call about waterproofing once it is dry.
A burst or leaking pipe. Shut the water off at the main and call a plumber.
Water coming up through a floor drain. That is the sewer or the septic system, not groundwater. Who to call depends on your neighborhood, and the local page lists them.
A stain on a ceiling. Roofs and upstairs bathrooms are a roofer's or a plumber's territory.
Wall cracks that are wide, stepped or bulging. Mention them, because water uses them, but the wall itself is a job for a foundation specialist or an engineer.

Worth writing down before you call

Where exactly, and on which side of the house
When you first noticed it
Whether it follows rain, and how quickly
Whether the house has a crawl space, a basement or both
Anything done before: a liner, a pump, new gutters