How do I keep water away from my foundation?

Keep water moving away from the house, in three places: the ground against the wall, the roof water coming down the gutters, and anything underground that collects water. Most wet basements are a result of water problems outside of the house,^[3] so this outdoor work protects the foundation and the basement together.

Looking and checking is yours to do, and the guidance below is Fairfax County's, written for Northern Virginia soils. Regrading, buried drain pipe and anything near the footings are contractor work, covered at the end.

The grade at the wall

Fairfax County's soil and water conservation district recommends a slope away from the wall: ideally, at least a 5% grade should be maintained for a distance of ten feet around your home.^[2] Put in plain numbers, over ten feet of horizontal distance from your foundation wall, there should be at least a 0.5 foot (six-inch) change in height.^[2] A negative grade tilts toward the house, which is an undesirable condition.^[2]

Walk the perimeter after a heavy rain and look for ponding, soggy soil or a dip against the wall. Backfill next to basement walls normally settles after several years, leaving depressional areas for water to collect.^[1] Fixing it is more than piling dirt, because the choice of soil and how it is placed and compacted both matter, which is why regrading is contractor work. See how a yard is regraded so water drains away from the house.

Roof water

A roof sheds far more water than people expect. When it rains hard, an average sized home can experience hundreds of gallons of runoff coming from the roof.^[4] The county's marine clay guide says to make sure the gutters and downspouts are in good condition and that they carry all roof water beyond the backfill or at least ten feet away from the house on splash blocks or through non-perforated pipe.^[1]

You can spot trouble from the ground. Inspect the outside of the gutters and downspouts for streaks or watermarks and look for erosion along the drip line;^[4] either means the gutters are overflowing and need attention. The destination matters too: whenever you redirect stormwater, make sure it is discharged to a suitable area.^[4] Sending it onto a neighbor's lot only moves the problem.

Everyday habits

• Keep big trees back. Large trees should be at least 20 feet away from the house.^[1]
• Do not leave a hose running by the wall. Do not leave outside water faucets or hoses running unattended, which can add large quantities of water to the soil next to the house.^[1]
• Check for leaks you cannot see. If you have a swimming pool, make sure that there are no leaks.^[1]
• Basement checks. Make sure your sump pump is turned on and functioning,^[3] and clear basement stairwell drain grates of leaf litter and debris.^[3]

When to call a licensed pro

Call someone when water still reaches the wall after the basics are right, or when the fix means digging beside the foundation. Sometimes springs or seepage areas occur near a house, or even below-ground next to the basement area. Subsurface drainage (drain pipe) may be needed to remove the water.^[1] Installing that, regrading a yard, or waterproofing a wall is excavation work with utilities and footings nearby, and the cause of a wet or cracked wall is better diagnosed first; see what cracks in a foundation mean and who to hire to check a cracked foundation.

Get written quotes that state the finished grade at the wall, where each downspout discharges, what pipe and fill are used, and who handles utility marking and any permit. Check licence classes: Class C contractors take single contracts over $1,000 but less than $30,000, and Class B contractors take single contracts of $30,000 or more but less than $150,000.^[5] Look the licence up before you sign.

Browse excavation services or more excavation answers. To collect quotes, describe the drainage job once and licensed local contractors can respond.