Most homeowners never measure the slope of their own yard. They notice a damp patch by the back door, a musty smell under the house, or dark soil that never quite dries out, and they guess. There is a fast way to stop guessing: a string, two stakes and a tape measure, run the same way a building inspector checks it. Ten minutes tells you whether your yard meets the state’s own drainage minimum or is actually carrying water toward your foundation.
California’s residential code sets a specific, testable minimum for the ground next to a foundation:
- 1The ground must fall at least 6 inches within the first 10 feet from the foundation wall — about a 5% slope (6 in ÷ 120 in).
- 2Paved surfaces (patios, walkways) within 10 feet of the foundation need at least a 2% slope away from the building.
- 3Where a fence, property line or existing slope makes that fall impossible, the code itself allows a drain or swale instead — the 6-inch fall is not the only legal option.
- 4This test tells you if there’s a problem, not the fix. A flat yard can sometimes be solved with regrading alone; a yard that has settled toward the house over years often needs a swale, area drain or French drain.
Why the direction of the slope matters
The California Residential Code addresses this directly in Section R401.3, Drainage: lots must be graded to drain surface water away from foundation walls, with the grade falling “not fewer than 6 inches within the first 10 feet.” It is a small rule with an outsized job. Every roof, patio and lawn on a property eventually sheds water somewhere, and the first 10 feet around the house decides whether that water leaves or stays. A yard that is flat, or that dips back toward the slab or crawl space, sends water exactly where you do not want it — against a stem wall, under a sill plate, or into a crawl space vent sitting close to grade.
The code also covers hardscape: impervious surfaces such as patios and walkways within 10 feet of the foundation need at least a 2% slope away from the building, a gentler number because concrete and pavers shed water faster than bare soil.
The 10-foot test, step by step
This is the same string-and-level method used to check grading work before it is signed off, adapted for a driveway-toolbox version: a tape measure, two stakes or wood scraps, mason’s string, and a line level (a small clip-on bubble level) or any level you can rest against the string.
- Step 1Stake at the wallDrive a stake or stick into the ground right at the foundation, at the spot you’re testing. Tie one end of the string to it at ground level.
- Step 2Stake 10 feet outMeasure 10 feet straight out from the first stake, perpendicular to the wall, and drive a second stake there. Tie the string to it, leaving slack.
- Step 3Level the stringPull the string taut. Clip a line level to the middle of the string (or hold a torpedo level against it) and raise or lower the string on the far stake until it reads level.
- Step 4Measure the dropAt the far stake, measure straight down from the level string to the ground. That number is your fall over that 10-foot run. Repeat at a few points around the house — grading is rarely uniform on every side.
What passing and failing look like
A tape measure gives you one number per spot you test, but a quick walk around the house usually confirms what the string already told you.
Slope is working
- The string test shows 6 inches or more of fall over 10 feet
- Paved areas within 10 feet of the wall visibly pitch away from the house
- Soil or mulch sits well below the top of the foundation stem wall, not banked up against siding or stucco
- A hose run near the wall for a minute visibly drains away, not toward it
Signs grading or drainage work is needed
- The string test shows less than 6 inches of fall, or the ground actually rises toward the house
- Standing water, dark wet soil or a musty smell near the foundation after rain
- Soil, bark or mulch piled up against siding, stucco or a crawl space vent
- A downspout or splash block dumping water within a few feet of the wall instead of carrying it away
Why yards end up sloping the wrong way
Few homeowners cause this on purpose. The common causes we see:
- Backfill settles. Soil placed against a foundation during construction is looser than undisturbed ground, and it compacts over the years, flattening or reversing the original grade right where it matters most.
- Added hardscape raises the near-house grade. A new patio, walkway or planting bed built up a few inches without matching the original slope can quietly tilt water back toward the wall.
- Mulch and soil build up over seasons. Topping beds year after year, without removing old material first, raises the grade closer to siding and weep screeds that were never meant to sit below soil level.
- The original grading was marginal on a flat lot. Some Bay Area lots are naturally close to level, so a builder’s grading that barely met the minimum can tip the wrong way after a single season of settling.
Our guide to grading and drainage for runoff problems covers the wider-yard version of this issue, beyond just the 10 feet nearest the house.
Matching the fix to what you find
The test tells you where you stand, but the right fix depends on why the fall is missing.
- Flat but open ground: if there is room to work with and nothing blocking it, re-establishing the fall is usually a grading job — cutting and building up soil to restore the slope. Our backyard grading cost guide and front yard grading guide cover what that typically involves.
- A fence, property line or structure blocks the 10-foot run: this is the exact situation the code’s own exception addresses — where physical barriers prohibit the 6-inch fall, a drain or swale takes over the job instead. That usually means a shallow channel or a buried pipe carrying water to a discharge point, covered in our French drain installation guide and our comparison of French drains, catch basins and dry wells.
- Water is coming off patios, downspouts or a low spot that won’t drain by gravity alone: an area drain basin set into the hardscape, tied into a pipe, catches water at the source instead of relying on sheet flow across soil.
A full yard drainage system combining grading, swales and buried drain lines is sometimes the right scope when several of these problems overlap on one property. Our guide to Bay Area drainage and irrigation solutions walks through how grading, drains and irrigation interact across a whole yard.
When to stop testing and call someone
A string test tells you about slope, not what is already happening underground. If you see water actively entering a crawl space or garage, cracking or separation in a slab or foundation wall, or soil that stays wet for days after rain stops, treat it as more than a weekend regrading project. Those signs can mean water has already been finding its way in for a while, and the fix may need to go deeper than the top 10 feet of soil.
Questions homeowners ask
What is the 10-foot drainage test?
It is a DIY way to check the grading rule in California’s residential code: using a level string stretched 10 feet from the foundation, you measure how much the ground drops over that distance. The code minimum is 6 inches of fall in the first 10 feet, roughly a 5% slope.
Is the 5% slope the same as the 2% rule I’ve seen for patios?
No, they’re two different surfaces in the same code section. Bare soil and lawn within 10 feet of the foundation need about a 5% slope (6 inches of fall over 10 feet). Paved, impervious surfaces such as patios and walkways within that same 10 feet need a gentler 2% slope, since hard surfaces shed water faster than soil.
What if a fence or my neighbor’s yard blocks the full 10 feet of fall?
The code anticipates this. Where lot lines, walls, slopes or other physical barriers make the 6-inch fall impossible, it allows a drain or swale to be built instead, as long as it still carries water away from the structure.
Can I regrade a small area myself?
Minor touch-ups, like adding soil to a spot that has settled, are within reach for many homeowners. Larger or whole-perimeter regrading involves moving enough soil that equipment access, where the removed soil goes, and matching slope into existing hardscape usually make it a job worth quoting rather than guessing at.
Does a yard that slopes away from the house guarantee no water problems?
No. Passing the 10-foot test means the soil grade meets the code minimum, but downspouts discharging too close to the wall, a low spot elsewhere in the yard, or a crawl space vent sitting near grade can still cause problems even on a yard that technically passes.
How do I know if I need a French drain instead of just regrading?
Regrading alone works when there is enough open ground to rebuild the slope. A French drain or area drain becomes the better option when a fence, structure or property line blocks the needed run, when water is concentrated (like a downspout or a low collection point) rather than sheeting across the yard, or when the soil itself drains slowly even on a correct slope.
Found a spot that fails the test?
Send us your measurements, or photos of the area, and we’ll help you figure out whether it’s a regrading fix, a drain, or both. Quartz Construction & Demolition holds California contractor license #1003436, which you can verify on the CSLB website.
Related services and guides
- ServiceBackyard grading
- ServiceFrench drain installation
- ServiceYard drainage systems
- GuideFrench drain installation guide
- GuideBackyard grading cost in the Bay Area
- GuideGrading and drainage for water runoff
Sources
Watch Our Work in Action
Watch our project videos on YouTube
Watch on YouTube- 2025 California Residential Code, Section R401.3, Drainage (UpCodes reproduction) — the 6-inch-in-10-foot grading minimum, the 2% rule for impervious surfaces, and the exception allowing drains or swales where physical barriers block the fall (checked October 9, 2026).
- Today’s Homeowner, How to Measure Grading Slope Around a House Foundation — the stake-and-string measuring method described in this guide.
- CSLB Check a License — verify any contractor’s license, including ours (#1003436).
General information, not an engineering evaluation, soils report or Quartz quote. The 10-foot test checks the grade only; it does not evaluate crawl space moisture, waterproofing or foundation condition. For active water intrusion or foundation damage, consult a qualified professional before relying on this test alone.
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