What to Do When Water Is Under Your House

Water under your house causes a range of problems, from mold and ruined insulation to soft floors and damaged framing. The good news is that it almost always has a findable source, and many of those sources are cheap to fix once you know which one you have. The longer the water sits, though, the more it costs.

There are only a handful of ways water gets under a house, and each leaves different evidence and needs a different fix. Here they are, roughly from simplest to most involved.

1. Gutters and Downspouts

Gutters gather a whole roof's rain into a few downspouts. If those empty at the base of the foundation, because an extension was knocked off or never installed, all of that runoff lands exactly where you don't want it. Overflowing gutters do the same along their whole length.

The evidence: water or silt staining on the inside of the foundation wall below a downspout, wet ground that lines up with a corner of the roof, and water that appears during or right after rain and dries out between storms.

The fix: clean the gutters, repair any that sag or leak at the seams, and carry every downspout well away from the house, either with extensions or with a buried line that discharges downhill. Sometimes this is the entire job.

2. Grading and Landscaping

The ground around a house should fall away from it, and over the years it often stops doing that. Soil settles next to the foundation, beds get built up with mulch and pine straw, and a patio ends up tilted back toward the house. Sprinklers that spray the foundation wall add to it.

The evidence: water that enters along one side of the house, often the uphill side, with mud lines or silt fanning in from that wall, and puddles that stand against the foundation after rain.

The fix: regrade so the soil slopes away, pull mulch and soil down below the siding, and adjust or turn off any irrigation that reaches the wall. If the lot itself slopes toward the house, or a neighbor's runoff crosses your yard, grading alone may not be enough, and a drain that catches the water before it reaches the foundation, such as a French drain, comes into it.

3. Groundwater and Saturated Soil

Some water never comes from the surface at all. Piedmont soil is weathered rock with a clay-rich layer that drains slowly. In a wet season the ground around a house fills up, and water moving through it takes the easiest route available, which can mean up through the crawl space floor or in through the foundation wall below grade. Homes on sloped lots or at the bottom of a hill tend to see more of it.

The evidence: wet ground spread across the whole crawl space rather than along one wall, water that lingers long after the weather turns dry, and a problem that is worse in winter and early spring than in summer.

The fix: give the water a way out. That usually means an interior drain along the inside of the foundation that carries water to a sump pump at the low point, which pumps it to a discharge well away from the house. An exterior French drain is the other option. Rule out the simpler sources first: a pump on top of an unfixed downspout problem just runs more often.

4. Plumbing Leaks

Supply and drain lines run through most crawl spaces, and a slow leak under the house can go unnoticed for months. So can an air conditioner condensate line that discharges into the crawl space instead of outside.

The evidence: a wet area concentrated in one spot, often under a bathroom, the kitchen or the laundry, that stays wet whether or not it has rained. A drain leak usually smells; a supply leak may not.

The fix: repair the leak, then dry the area and replace any insulation, subfloor or framing it ruined. The leak is a plumber's job; the damage it leaves in the floor system is ours.

5. Humid Air and Condensation

Not all of the water under a house arrived as liquid. In a vented crawl space, warm, humid summer air comes in through the foundation vents, meets cool ductwork, pipes and framing, and gives up its moisture as condensation, the same way a cold glass sweats on a hot day. Bare soil adds more, because water vapor rises out of the ground all year.

The evidence: sweating ductwork, insulation sagging out of the joists because it is wet, damp wood with no puddle beneath it, and a problem that peaks in late summer.

The fix: stop feeding the space with humid air and ground moisture. A sealed vapor barrier over the soil, closed foundation vents and a dehumidifier sized for the space, together known as crawl space encapsulation, keep it dry. More ventilation makes it worse here, because the incoming air is the source.

Cracks and Gaps Are the Door, Not the Source

Cracks in the foundation wall, gaps around pipes and failed vent seals are where water gets in, but rarely why it is there. Seal a crack without dealing with the water outside and the leak tends to move along the wall. Fix the source first.

Why Standing Water Under Your Home Is a Problem

Water under the house doesn't stay contained down there. It raises humidity throughout the home, rots framing and subfloor, flattens insulation, invites mold and wood-destroying insects, and makes your heating and cooling work harder. Left long enough, it weakens floor joists and support piers, turning a moisture problem into a structural one.

When water has already caused structural damage, such as settling piers or rotted joists, that is a more involved repair. Triangle Reconstruction works with structural engineers who can inspect the damage and write an approved repair plan before any structural work begins.

Finding Out Which One You Have

Plenty of crawl spaces have more than one source at once. That is why, when we look at water in your crawl space, we walk the outside of the house as well as the space underneath it. The symptom is under the floor; the cause is usually outside.

Wondering whether you need a pump? Our guide to whether your crawl space needs a sump pump shows how to read the marks past rain left behind.

Triangle Reconstruction has been fixing water under houses across Wake and Durham counties and every county bordering them since 2012. Found water under yours? Photograph it, note the weather, and call (919) 924-7600.