Making sure water drains away from the foundation

Water that sits against a foundation has an easy route into the house. Saturated soil can press on basement walls, water can seep through cracks and joints, and damp ground around a crawlspace or slab edge can bring moisture indoors. The goal is to move water away from the house quickly and keep it moving. That depends mainly on the slope of the ground beside the house, on where the gutters and downspouts discharge, and on whether anything near the walls holds water against them.

Check the slope of the ground

The ground next to a house should fall away from the foundation. Building codes commonly call for the grade to drop about six inches within the first ten feet from the wall. You can check this with a straight board about ten feet long and a level. Set one end of the board on the ground at the wall, hold the board level, and measure the gap between the board and the ground at the far end. Repeat the measurement at the corners and at the side of the house where the yard tends to stay wet. Stepping back during a rain and watching where the water goes is a useful companion check. Ground that slopes toward the house, or stays flat for several feet, holds water in exactly the places where it does the most harm.

The soil type changes how much the grade matters. Clay soils drain slowly and hold water close to the surface, so a grade that looks adequate can still pool after a heavy storm. Sandy soils drain quickly, but water still needs a route away from the wall if it is arriving from the roof or the yard. A drainage contractor who visits the site can tell you how the soil behaves and what regrading or drainage work it calls for.

Soil settles over time, especially in areas that were backfilled after construction. A yard that was graded well when the house was built can develop low spots along the wall, and those low spots collect water every time it rains. Fill them with soil added in thin layers, lightly compacting each layer so the new soil does not sink again. Slope the fill gently away from the wall, and keep it several inches below any wood siding or trim, because soil touching wood invites rot and insects.

Direct the water away from the wall

Gutters and downspouts do much of the work, so their discharge matters as much as the ground itself. Use extensions or underground drains to carry water several feet from the house, and check that splash blocks sit on sloping ground rather than draining back toward the wall. A downspout that empties at the base of the wall simply moves the problem to the foundation.

Other common sources deserve the same attention. A patio or walkway that slopes toward the house sends water straight to the foundation, and a sprinkler head that sprays the wall keeps the soil saturated. Window wells need drainage that carries water away from the glass and the frame. The condensate drain line from an air conditioner should discharge away from the foundation, because a steady drip at one spot can keep the soil wet for the whole season. Garden beds and raised planters should sit a short distance from the wall, or be built with a gap, so water does not pool behind them. Mulch piled against the foundation traps moisture in the same way, so keep a narrow strip of gravel or bare soil along the wall.

Test the water and know when to get help

A simple hose test shows how water moves. Run a garden hose at a moderate, steady flow near the foundation for several minutes, then watch where it goes. Water should flow away from the house and soak in or drain off, not pool beside the wall or run back toward it. Do not leave the hose running unattended, and avoid directing a flow toward a window well or a basement entrance.

The ground farther out matters too. Water that runs off a neighbor's yard, a driveway or a sloping lot can reach the house from a direction the downspouts never touch. Walk the property after a rain and note where water arrives at the boundary as well as where it collects against the house. Water entering from upslope often needs a shallow swale or a line of drainage that intercepts it before it reaches the foundation, and the fix is usually a matter of redirecting the flow rather than blocking it.

Some signs point to a problem that needs a professional look. A basement or crawlspace that is damp after rain, a white powdery residue on masonry known as efflorescence, cracks that widen over time, doors or windows that begin to stick, or new stair-step cracks in brick or block walls all call for a closer inspection. A licensed structural engineer or an experienced drainage contractor can diagnose the cause, and a foundation repair contractor can explain the options. Grading and downspout fixes are inexpensive and often help, but they do not confirm what is happening inside a wall or beneath a slab, so general guidance cannot replace an on-site assessment.

Walk the perimeter after the next heavy rain and note where water collects, where it stands for longer than an hour, and which downspouts or drains send it back toward the house. Make one change at a time, and repeat the walk after each change to confirm that the fix moved the water in the right direction. Ground that drains well is one of the least glamorous features of a home, and it is one of the most important for keeping the foundation and the lower walls dry.