The finished ground around a house is supposed to slope away from the foundation so rain and snowmelt drain off, a commonly cited target is roughly 150 mm (about 6 inches) of fall over the first 1.5 to 3 m (5 to 10 ft). "Negative grading" is the opposite: ground that slopes toward the house, usually made worse by downspouts that discharge right at the foundation.
$500 to $3,500 regrading / downspout extensions ($5,000 to $10,000+ for major slope or drainage work)Address soonExteriorStructure
The quick answer
Negative grading is ground (or downspouts) that sends water toward the foundation instead of away, the single most common, most preventable cause of wet basements. It's also one of the best value fixes a buyer can act on: regrading and extending downspouts usually runs $500 to $3,500. Watch for pooling and white efflorescence on the basement walls; if water's already getting in, have the cause assessed.
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Why it matters
CMHC guidance is explicit that grade should slope away from the structure to direct surface water off the foundation, because directing water to the foundation is the single most common, most preventable cause of wet basements and foundation problems. Water pooling against the wall finds its way in, and over years can contribute to cracking or movement. The fix is usually cheap; the damage if ignored is not, which makes this one of the best value-for-money items a buyer can act on.
How to spot it
Ground sloping toward the walls; mulch, soil, or patios built up above the foundation line; downspouts ending right at the wall with no extension; and inside, pooling, staining, or efflorescence (white mineral powder) on the basement walls below those spots.
What it costs
Downspout extensions are nearly free; small slope fixes run $500 to $1,500; regrading around the full house typically $2,000 to $3,500; large projects combining steep slopes, soil removal, or drainage systems reach $5,000 to $10,000+. (Published pricing is US-market. Treat as a ballpark and get local quotes.)
What to do
Address soon, it's high-value-for-cost. Extending downspouts well away from the house and regrading low spots to slope away are the usual fixes, and watching the basement after the next heavy rain tells you a lot. But if there's any sign water has already been getting in, staining, efflorescence, or cracks, have it assessed by a foundation or drainage professional rather than assuming it's only a grading fix.
Education and triage, not a home inspection. Casaroo flags the slope and downspout discharge from your photos, easy to confirm in person and usually inexpensive to correct. If water has already been getting in, a home inspector or foundation professional should confirm the cause and extent. We flag; we don't inspect.
Common questions
Is regrading really that cheap a fix?
For what it prevents, yes. Downspout extensions cost almost nothing and regrading around a house typically runs $500 to $3,500, against wet-basement and foundation damage that runs into the tens of thousands. It is one of the best value-for-cost items a buyer can act on.
How do I check the grading myself?
Walk the perimeter and look at which way the ground falls in the first few feet from the wall. Then look for the tells inside: pooling, staining, or white powdery efflorescence on the basement wall below the low spots.
Water has already been getting in. Is grading still the fix?
It may be part of it, but do not assume. If there is staining, efflorescence, or cracking, have a home inspector or a foundation and drainage professional confirm the cause and extent, because you could be looking at a bigger problem than slope.
Should I ask the seller to regrade?
A credit is usually cleaner, because you want the work scoped properly rather than done fast before closing. What you should ask the seller is whether the basement has ever taken water, and get the answer in writing.
Last reviewed 2026-07-10.
This guide is general education, not a home inspection and not advice for your specific property. Always
consult the appropriate licensed professional, and get a licensed home inspection before you remove conditions
or buy. Cost ranges are 2026 estimates that vary by region, size, and access; confirm specifics with a
qualified professional.