What Grading Means and Why It Matters
Grading is just the slope of the ground around your house. Positive grading means the ground slopes away from the foundation, carrying water away. Negative grading means it slopes toward the foundation, delivering water right to your basement walls.
The International Residential Code recommends a minimum slope of 6 inches over the first 10 feet from the foundation. That's not steep. It's barely perceptible visually. But it makes an enormous difference in where water goes during a heavy rain.
According to the American Society of Home Inspectors, drainage problems are among the most common deficiencies found in home inspections. By my count, roughly 60% of the homes I inspect have some form of grading or drainage issue.
How Grading Goes Wrong
New houses usually have correct grading. The builder grades away from the foundation because the inspector will check it before issuing the certificate of occupancy.
Then time passes. Mulch builds up against the foundation year after year. Landscaping changes the contours. That decorative stone bed settles. The soil along the foundation compacts from foot traffic. Trees mature and roots change drainage patterns. After 10 or 20 years, a lot of homes have grading that no longer works.
Signs of Drainage Problems
Basement water is the obvious symptom, but it's not the only one. Grading issues leave calling cards all over the place if you know where to look.
The Standing Water Test
Walk the perimeter of your house during or right after a heavy rain. Where does water pool? Does it collect against the foundation? Does it run toward the house from the lawn? That's your drainage system telling you it's broken.
I do this during every inspection if I'm lucky enough to be there during rain. It reveals more about the drainage than any amount of studying the dry ground.
Erosion Patterns
Look for channels where water has cut into the soil. Washed-out mulch. Sediment deposits against the foundation. Bare spots in the lawn where water flows concentrate. These patterns map the water's path, and often that path leads straight to the foundation.
Staining on Foundation Walls
Water lines, mineral deposits, and discoloration on the exterior foundation wall tell you how high water has risen against the house. Dark staining at the base is normal. Staining several inches up indicates ponding.
Interior Evidence
Musty basement smells. White mineral deposits (efflorescence) on basement walls. Water stains on the lower portion of walls. Actual water intrusion, either puddles or seepage. Humidity issues. Mold growth. All of these can trace back to exterior grading problems.
The Downspout Problem
I've said it a thousand times: downspouts are the number one drainage issue I find. The gutter system does exactly what it's designed to do. It collects water from several hundred square feet of roof and concentrates it into a few discharge points. Then people dump all that concentrated water right against their foundation.
A roof sheds roughly 600 gallons of water per 1,000 square feet of roof surface per inch of rain. The average house might have 2,000 square feet of roof draining to 4-6 downspouts. That's hundreds of gallons coming out of each downspout during a storm, and it's all landing within inches of the foundation.
The Minimum Extension Rule
Downspouts need to discharge at least 6 feet from the foundation. Ideally 10 feet. More if the ground slopes back toward the house.
The extensions don't have to be fancy. Those green corrugated tubes from the hardware store work fine. Underground drain pipes are more elegant but cost more. Even a splash block is better than nothing, though it's the minimum acceptable solution.
Tom's Gutters Revisited
Tom's situation is common. His downspouts ended with short elbows pointing away from the foundation, maybe 6 inches of offset. In theory the water would just run away from the house. In practice, the volume was too much, and it pooled right at the foundation before running toward the backyard swale.
After cleaning his gutters and adding 6-foot extensions, he hasn't had water in his basement since. That was four years and several major storms ago.
The Landscaping Trap
Landscaping causes more grading problems than people realize. Beautiful beds and carefully placed plants can funnel water exactly where you don't want it.
Flower Beds Against Foundations
Raised flower beds against the foundation create dams that trap water. The amended soil holds moisture. The edging blocks drainage. Even when the original grading was correct, the bed creates a bowl that collects water right at the foundation wall.
My sister-in-law Linda spent $3,000 on landscaping that included raised beds wrapping around her foundation. Two years later she spent $4,000 on waterproofing. The beds looked beautiful. They also held water against her basement walls all summer.
Mulch Buildup
Adding 2-3 inches of mulch every year seems harmless. After 10 years, you have 12 inches of mulch and the grade now slopes toward the house. I see this constantly. The original grade was fine, but a decade of mulch has reversed it.
Pull back the mulch every few years. Never let it build up higher than 2-3 inches. And keep it away from the siding by at least 4-6 inches.
Hardscape Directing Water Inward
Patios, walkways, and driveways can slope toward the house if installed improperly. A concrete patio that tilts even slightly toward the foundation delivers hundreds of gallons per storm directly to the basement walls.
Check for daylight under a level placed on flat surfaces near the house. Any slope toward the foundation is a problem.
Fixing Grading Issues
Solutions range from free to expensive. Start with the cheap stuff because it often solves the problem.
Level One: Downspout Extensions
Cost: $5-15 per downspout for basic extensions, up to $100 each for underground buried lines.
This is always the first recommendation. Extend every downspout at least 6 feet from the foundation. If the yard slopes back toward the house, go further. Make sure the discharge point is on ground that drains away, not into another low spot.
Level Two: Adding Soil and Regrading
Cost: $200-1,000 for DIY materials, $1,500-5,000 for professional regrading.
Adding topsoil along the foundation to create proper slope is often sufficient. You want 6 inches of fall over the first 10 feet, tapering down to the existing grade. Use clean fill dirt, not topsoil with organics near the foundation. Top with a thin layer of topsoil only if you're planting grass.
This works best when the issue is modest. If the ground currently slopes toward the house, you might need to remove soil before adding it back at the correct grade.
Level Three: French Drains
Cost: $1,000-4,000 for a typical installation.
A French drain is a gravel-filled trench with a perforated pipe that collects subsurface water and carries it away. These help when the water table is high or when surface grading alone can't solve the problem.
French drains need somewhere to discharge. That might be a dry well, a storm sewer connection if allowed, or just daylight at a lower point in the yard. They also need periodic maintenance as the pipe can clog with sediment over time.
Level Four: Interior Drain Systems and Sump Pumps
Cost: $3,000-10,000 depending on scope.
When exterior solutions aren't practical or sufficient, interior drain systems collect water that enters the basement and pump it away. These don't stop water from reaching the foundation. They manage it after it gets there.
For some homes, particularly those with high water tables or older stone foundations, interior management is the most practical approach. But I always recommend trying exterior solutions first. It's better to keep water out than to deal with it after it gets in.
What I Tell Home Buyers
Grading issues show up in most of my inspection reports. I try to put them in context for buyers who sometimes panic when they see "drainage concerns" in writing.
The vast majority of grading problems are maintenance issues, not defects. Extend the downspouts. Add some soil and reshape the grade. These are weekend projects, not emergencies.
Active water intrusion is more serious and requires investigation. But even then, the solution is usually exterior drainage improvement, not foundation repair. I've seen sellers quote $15,000 for foundation waterproofing when $500 in grading work would have solved the problem.
The Questions to Ask
Has the basement ever had water? When and how much? What was done about it?
Sellers are required to disclose known water intrusion. Their answers, combined with my inspection findings, paint a picture of whether this is a minor issue or something larger.
A bone-dry basement in a house with poor grading might just mean the sellers got lucky with weather. Or it might mean they're good about managing their gutters. Either way, fix the grading. Don't wait to find out the hard way.
The Long Game
Drainage isn't a fix-it-once situation. It's ongoing maintenance. Grades change as soil settles. Landscaping grows and alters drainage patterns. Downspout extensions get knocked off or crushed by lawn mowers.
Walk your property after heavy rains once or twice a year. See where water goes. Make adjustments before problems develop. The house that stays dry is the house whose owner pays attention to water management.
Tom checks his gutters now. Every spring and fall, like clockwork. He's become almost evangelical about downspout extensions. Last month he helped his other neighbor install them after seeing puddles against her foundation.
"You were right," he told me. "It's not about the foundation. It's about where the water goes."
Took him a flooded basement to figure that out. Hopefully you're reading this first.