Foundation Grading Basics — Sloping the Ground Away From Your House

Grading is the slope of the soil around your house, and it should fall away from the foundation for the first several feet so rain drains off into the yard instead of pooling at the wall. It is the cheapest and most fundamental defense you have against basement and crawl-space moisture — nothing else you do to manage roof water works well if the ground itself is sending water back toward the house.

This guide is about drainage: shaping the ground so water leaves the house on its own. That is different from waterproofing, which seals the below-grade structure against water that has already reached it. Keep the two separate in your mind. Grading is where most homeowners should start, and it’s work you can usually do yourself — with one important exception we’ll come back to at the end.

What “grade” actually means

The grade is the slope of the finished ground surface. Around a foundation, the direction of that slope is what matters.

• Positive grade falls away from the house. Rain that lands near the wall runs downhill into the yard.
• Negative grade tilts toward the house. Rain collects against the foundation, soaks into the soil, and feeds moisture into the basement or crawl space.

Negative grade is the single most common reason water pools near a foundation. Sometimes the house was built that way; more often the soil started out sloping away and then settled. Backfill placed against a foundation during construction is loose, and over the first several years it compacts and sinks. A strip of ground that once shed water can quietly settle into a low pocket that holds it.

The common slope guideline

You’ll often see a specific target: the ground should drop about six inches over the first ten feet away from the wall. That’s a useful mental picture, but treat it as a common guideline rather than an absolute rule. How much slope you actually need — and how much you can create — depends on your soil and your local code.

The practical test cuts through the numbers: after a rain, water should visibly run away from the wall. If it does, your grade is doing its job, whatever it measures.

How to check your grade

You don’t need surveying gear. Three simple checks tell you almost everything.

1. Watch during a steady rain. This is the most honest test there is. Put on a raincoat and look at where water goes near the wall. Is it running off into the yard, or collecting against the foundation? Where does it pool?
2. Run a string line or use a level. Drive a stake at the wall and another several feet out. Tie a string between them, hang a line level on it, and measure the drop from the wall to the far stake. Or lay a carpenter’s level on a straight board laid on the soil. Either way you’re checking that the ground falls away, and roughly how much.
3. Look for the tells afterward. Standing puddles a day after a storm, a visible trough or low spot along the wall, water stains or a mud line on the foundation, and soil that has slumped away from the house all point to a grade that isn’t shedding water.

Sign	Grade	What it means	First move
Water runs off into the yard during rain	Positive	Slope is working	Maintain it; watch for future settling
Puddles sit against the wall after storms	Negative	Water is collecting at the foundation	Build up and re-slope the first several feet
Visible low spot or trough along the wall	Negative	Soil has settled into a pocket	Top-dress and compact to restore the slope
Mud line or staining on the foundation	Negative	Water is repeatedly reaching the wall	Regrade and check downspout discharge
Downspout dumps into a low area at the wall	Negative	Roof water is being concentrated at the base	Extend the downspout onto the graded slope

How to fix a negative grade

The fix is straightforward in principle: add soil against the house and shape it so the ground falls away. The details are what keep it from causing new problems.

Build the slope, then compact it

Add fill soil near the wall and taper it down and out into the yard, so the finished surface falls away consistently. Compact it as you go — loose soil will settle right back into the low spot you’re trying to fix. Many people use a firmer, clay-rich fill near the wall to shed water, then a few inches of topsoil over it to support grass. For a settled low spot, this is really just top-dressing: adding soil to rebuild the slope the ground has lost.

Keep soil below the siding and damp-proofing line

This is the rule that matters most, and the easiest to get wrong.

If your low spot is so deep that fixing the slope would bury the siding, you can’t simply keep adding dirt. That’s a sign the grade needs to be reworked farther out into the yard — or that the problem is bigger than surface soil and worth a closer look.

Give the roof water somewhere to land

Grading and downspouts work as a pair. A downspout that discharges right at the wall dumps a roof’s worth of water onto the very ground you just shaped, overwhelming it in one spot. Extend downspouts so they discharge onto the graded area, several feet out, where the slope can carry the water away. Our guide on how far downspouts should extend covers target distances. Good grading and good discharge together are what actually keep the soil against the wall dry.

Mind the hardscape

Patios, driveways, and walkways are graded surfaces too. If a slab was poured sloping toward the house, it sheds water straight to the foundation no matter how well the surrounding soil drains. You usually can’t re-slope a slab, so the fix is to catch the water at the edge — a channel drain, or regrading the strip of soil where the hardscape meets the house — rather than fighting it with soil alone.

Grading is the cheapest, most fundamental drainage fix there is

Top-dressing a settled low spot needs no special tools or permits

Done right, a restored slope lasts for years

Flat lots and clay soil limit how much slope you can create

New fill settles, so it needs compacting and later top-ups

Grading won't help water that's already coming through the wall

Common mistakes

A few well-meant moves cause new problems or hide the real one.

• Piling soil against the siding. The most common error. Chasing a puddle by heaping dirt up the wall buries siding and damp-proofing and traps moisture against them. Keep the grade below that line, always.
• Burying the problem instead of moving the water. Dumping gravel or mulch into a low spot hides the puddle without changing where the water goes. The soil against the wall still gets soaked.
• Ignoring settled areas. Backfill keeps settling for years. A grade you fixed once can sink again, so re-check the first few feet after a few seasons and top it up.
• Skipping the “watch during rain” step. Regrading before you’ve confirmed the water is actually a grading problem — and not, say, an overflowing gutter — is how people spend a weekend on the wrong fix.
• Draining toward a neighbor or a walkway. Solving your slope by pushing water onto someone else’s lot, or across a path where it will ice over, just relocates the problem.

When grading is a job for a professional

Reshaping soil against a sound foundation is DIY-friendly. Reshaping it against a foundation that’s in trouble is not.

If the wall you’re grading against shows cracks — especially horizontal cracks, stair-step cracks in block, or cracks that are widening — or looks like it’s bowing, leaning, or settling, stop. Those are structural signals, and grading is only one small part of the picture. Adding soil against a moving or cracked wall can even mask a problem that needs attention. Chronic water that keeps reaching the basement after you’ve corrected the grade points the same direction: something below grade needs a professional’s eyes.

In those cases, a foundation or waterproofing professional should assess the wall before you build soil against it. This guide can help you shed surface water off a healthy foundation; it can’t diagnose a failing one, and neither can a bag of topsoil.

The short version

Grading is the slope of the soil around your house, and the goal is simple: get the first several feet to fall away from the wall so rain leaves on its own. Check it by watching during a rain and running a string line, aim for a slope that visibly sheds water — the six-inches-over-ten-feet guideline is a starting point, not a rule — and build it up while keeping soil well below the siding and damp-proofing line. Point your downspouts onto that graded ground, and if the water keeps reaching the wall you may be dealing with a basement that gets wet after rain for reasons that run deeper than the surface. And if the foundation itself is cracked or moving, that’s where DIY grading ends and a professional begins.