Grading and drainage around your home

Water that collects next to a house finds its way into crawl spaces, basements and the bottom of walls. Over time it can lead to damp crawl spaces, rot, termites and foundation movement. Most of the fix happens outside: the ground should slope away from the house, and roof water should land far enough out that it keeps moving.

"Grading" is the shape of the ground around the house. "Negative grading" means the ground slopes toward the house instead of away from it. This guide explains what good drainage looks like, how to spot problems and what the fixes are. For what the work costs, see tree trimming, grading and fence repair.

What good grading looks like

Building codes based on the International Residential Code require lots to be graded so surface water drains away from foundation walls. A typical version of the rule says the ground must fall at least 6 inches within the first 10 feet from the house. [2] Texas foundation engineering guidelines recommend the same minimum, a 5 percent slope, or 6 inches in 10 feet. [3] ENERGY STAR guidance for new homes calls for at least half an inch of fall per foot over the first 10 feet. [1]

Hard surfaces like patios, walkways and driveways should also slope away from the house, at about 2 percent near the foundation, or have a drain. [1] When the house is too close to a property line or wall for a 10-foot slope, a swale (a shallow, grassy channel) or a drain is used to carry water around and away. [1]

The exact rules depend on your local code. If you are changing grading near a property line, check with your local building department, because codes also say grading must not cause flooding or damage on a neighbor's property. [2]

How to check your grading

Watch it rain. The easiest test is to walk around the house during or right after a heavy rain. NC State Extension suggests checking for water pooling around the foundation. [4]
Look for clues on a dry day. Bare soil washed away at the base of the walls, mulch beds piled higher than the lawn, soil touching the siding and stains on the bottom of the foundation all point to water collecting near the house.
Measure the slope. Drive one stake at the foundation and another 10 feet out. Tie a string between them, level it with a line level, then measure from the string down to the ground at the outer stake. You want 6 inches or more.
Look under the house. Damp soil, standing water or white powdery deposits on the crawl space walls after rain often trace back to grading and downspouts. See the foundation and structure guides for crawl space moisture.

Downspouts are part of the grading

A roof sheds a lot of water, and gutters collect it into a few spots. If those downspouts empty right at the foundation, even good grading can be overwhelmed.

Extend them. NC State Extension says downspouts should extend 6 to 10 feet from the foundation. [4] Texas engineering guidelines also recommend extending downspouts well past the foundation. [3]
Send the water somewhere useful. Building America guidance says downspouts should discharge to an approved location such as a swale or dry well. [1] If water runs through a buried pipe, the pipe needs an open outlet at a lower point than where it starts. [5]
Keep gutters clear. Gutters and downspouts should be intact, free of debris and directing water away from the house. [4] Clogged gutters overflow along the wall.
Mind the sprinklers. Lawn sprinklers should water the grass, not the house, and plantings along the foundation should not be overwatered. [4]

For gutters and roof drainage, see the roof guides.

The fixes, from small to large

Fix	When it fits
Extend or redirect downspouts	Water collects at downspout spots
Pull mulch and soil back from the siding	Beds are piled against the house
Add soil and reshape the slope near the house	A few low spots or gentle negative grading
Dig a swale	Water from the yard or a neighbor runs toward the house, or there's no room to slope 10 feet
Add a drain at the base of a patio or driveway	A hard surface slopes toward the house [1]
Install a French drain	Water keeps collecting in one area even after the surface is reshaped
Regrade a whole side of the house	The ground slopes toward the house across a large area

Small reshaping. When soil is added near the house, it should be firm, packed soil shaped to slope away, not loose mulch. ENERGY STAR guidance calls for tamping backfill so it doesn't settle and finishing with a layer of silty clay. [1] Keep the finished soil below the bottom of the siding. See our guide on what kind of siding you have for clearance tips.

Swales. A swale is a wide, shallow channel that carries surface water around the house to a lower spot, such as a ditch, storm drain or dry well. [1]

French drains. A French drain is a sloped trench with a perforated pipe, wrapped in fabric, covered in gravel. Water soaks into the gravel, enters the pipe and flows downhill to an outlet. Mississippi State Extension notes that the outlet must sit lower than the area being drained, and the pipe should lead to a drain, ditch or street. [5] A French drain doesn't fix a slope that runs toward the house, so it usually works alongside grading, not instead of it.

Regrading. Reshaping a large area after a house is built is a bigger job. The Department of Energy's building guidance calls it "a difficult and expensive process" and lists alternatives, such as footing drains, swales and drains at the base of hard surfaces. [1] Before any digging, call 811 to have underground utilities marked.

A note for clay soils

In areas with clay soils that swell when wet and shrink when dry, including much of Texas, steady soil moisture around the house matters as much as drainage. Texas foundation guidelines recommend keeping soil moisture fairly even on all sides of the house and avoiding overwatering. [3] Moisture swings can move a foundation. The foundation and structure guides explain what to watch for.

When to get help

Small fixes like downspout extensions and pulling back mulch are often simple. Larger regrading, swales and French drains take planning so water ends up in the right place and not on a neighbor's lot. Water near a driveway is its own issue: see driveway draining toward the home and driveway, walkway and patio repair.

HomeCloud is a licensed general contractor that evaluates homes and prices and does the repairs. We can look at how water moves around your house and send you a priced estimate.