How to make rainwater drain away from the foundation
Good grading away from foundation walls means the ground falls at least 6 inches within the first 10 feet. Check it with a straight board and a level, watch where water goes in the rain, and extend downspouts so they empty well away from the house. Add soil where the slope runs backward.
Why grading away from foundation walls matters
You're checking whether the land carries water away from your walls or toward them. The building code's standard is simple. Massachusetts' version says lots must be graded to drain away from foundation walls, with the ground falling at least 6 inches within the first 10 feet. That's a 5% slope. Many places use the same number, but local codes vary.
Soil settles, especially beside a new foundation, and landscaping changes things over time. So a house that met this rule when it was built may not meet it now.
Roof water is the other half of the job. A roof sends a lot of water to a few points, and if each downspout empties at the wall, good grading can't fully keep up.
Guidance on how far out to send it varies. University of Georgia Extension says 2 to 3 feet from the house. NC State Extension says 6 to 10 feet. If your basement or crawl space ever gets wet, aim for the longer distance.
How to check grading away from foundation walls
- Walk the house after rain
Note where puddles sit, and take photos with the date on them.
- Measure the slope
Hold a 10-foot straight board level from the wall. Measure the gap to the ground at the far end. Repeat on each side.
- Follow each downspout
During rain, see where it empties and which way the water goes.
- Add extensions
Fit extensions or splash blocks so the water lands well away from the wall and runs downhill.
- Build up low spots
Add soil where the ground slopes back toward the house. Compact it and shape it to fall away.
- Check nearby paving
Look at patios and walks that touch the house. If they've tilted toward the wall, ask a contractor about the fix.
- Retest in the next storm
Soil settles, so look again after the next few rains and top it up if needed.
How much slope away from the house is enough?
Lay a 10-foot straight board out from the wall, level it, and measure from the far end down to the soil.
| Reading at 10 feet | What it means | What to do |
|---|---|---|
| 6 inches or more | Meets the usual code minimum | Leave it, and recheck every year or so |
| Less than 6 inches, still falling | Weak slope | Add soil near the wall and shape it to fall away |
| Flat | Water can sit against the foundation | Regrade, or add a swale if you can't get the slope |
| Ground rises away from the wall | Water runs toward the house | Regrade. Get a pro's opinion if the yard is tight. |
In heavy rain, take a look outside with an umbrella. A few minutes in the rain will teach you more than a dry day of measuring.
- Puddles against the wall that linger after the rain: the slope is failing there
- Water spilling over gutters: clean them, and EPA says to keep them repaired too
- Downspout water flowing back to the house: extend it or change the route
- Water running onto a neighbor's lot or a shared walkway: redirect it
How to fix yard drainage and low spots
Small fixes are DIY. Use compacted soil for the fill, since mulch won't move water away. Build up the low spots and slope the surface outward.
Before you do bigger work, check with your local permit office and floodplain administrator, as FEMA advises. Your changes can't push water onto neighbors, and Massachusetts' code says so outright. Call 811 before any digging, even for a shallow trench.
Tight lots are a job for a pro. Where a lot line, wall or patio blocks the slope, a contractor can usually add a swale or drain.
Don't tie drains or a sump pump into the sanitary sewer. The Insurance Information Institute says doing so is illegal and can clog the line. If a plumber finds that kind of connection, have it moved.
Stop and call a licensed structural engineer or foundation professional if you see cracks that grow, bowing walls or doors that suddenly stick. FEMA notes wall cracks can mean damage from earth pressure outside. Drainage work helps, but it doesn't repair structural damage.
What homeowners say about regrading a yard
Also check where the AC condensate line drains. It should empty away from the house. A steady wet spot next to the foundation attracts carpenter ants and termites. (Reddit)
Keep the soil at least 6 inches below the siding, and keep plants and mulch from touching it. (Reddit)
Owners in two countries agree that keeping water away from the foundation is the usual answer to a wet basement. Re-slope the soil, extend the downspouts, and fix the drainage before spending on waterproofing. (Hacker News)
How far should downspouts drain, and other questions
How much should the ground slope away from a house?
A common code standard is at least 6 inches of fall within the first 10 feet, which is a 5% slope. Check your local code, because rules and exceptions vary by state and city.
How far should downspouts drain from the house?
Guidance varies. University of Georgia Extension says 2 to 3 feet, and NC State Extension says 6 to 10 feet. Farther is better for a wet basement, as long as the water runs downhill and away from neighbors.
Can I regrade my yard myself?
You can usually fix small low spots along the wall. Check with your local permit office before larger changes, call 811 before you dig, and make sure the new slope won't send water onto a neighbor's property.
Sources: law.cornell.edu, FEMA, content.ces.ncsu.edu, fcs.uga.edu, EPA, Insurance Information Institute
General guidance for U.S. homes, not professional advice. For gas, electrical and structural work, call a licensed pro.