After rain or snowmelt
Keep roof runoff away from your foundation.
By Beau Brown, C&H Inspections · November 9, 2026
A roof collects a lot of water. Where that water lands matters. Beau explains the backfilled zone around a foundation—the “moat” in the video—and how gutters, downspouts, and ground slope can keep runoff from collecting beside the house.
1 minute 29 seconds · homeowner education
The hole gets filled. The water still needs a way out.
Construction often disturbs the soil beside a foundation. Backfill can settle, and its drainage behavior may differ from the surrounding soil. A low spot next to the wall can become a place where runoff collects.
The “moat” is a teaching analogy, not a literal feature beneath every home. Soil type, compaction, foundation design, groundwater, and drainage systems all affect what happens. Properly selected and compacted backfill is part of good construction.
One inch of rain can mean about 1,250 gallons.
That is the potential water volume from a roof with a 2,000-square-foot horizontal footprint: 2,000 × 1/12 × 7.48 ≈ 1,247 U.S. gallons. It is not a claim that all that water enters the backfill or basement. Gutters, storage, surface drainage, and where the outlets discharge change where it goes.
After the weather clears, follow the water.
Wait until it is safe to walk outside. Stay off ladders and roofs, keep clear of slippery or flooded areas, and observe these details from the ground.
- Gutters: overflow marks, drips, or a concentrated splash area may point to a blockage, leak, or capacity issue.
- Downspouts: note missing or disconnected extensions and where the outlet sends the water. A long extension is not useful if the water runs back toward the wall.
- Ground beside the foundation: settled beds, low spots, ponding, or soil that slopes toward the house are worth documenting.
- Connected surfaces: patios, walks, window wells, and landscaped borders can interrupt the route away from the house.
- Accessible indoor clues: record where and when basement dampness follows a storm. Do not enter standing water or a wet area near electrical equipment.
Gutters and grading work together.
A common residential grading benchmark is a fall of 6 inches in the first 10 feet of soil away from a foundation. Where space or barriers prevent that slope, a designed swale or drain may be needed. Local requirements, paved surfaces, and site conditions matter; this is not a universal retrofit instruction.
The video shows a 4-foot-plus downspout extension. Treat that as an illustration, not a guaranteed safe distance. Building America guidance describes discharge to sloping grade at least 5 feet away, or suitable designed collection farther away. The outlet needs a real route away from the house and an approved destination—not a neighbor’s property.
Inspector tip
Photograph recurring puddles, gutter overflow, and seepage while the clues are visible. A home inspection can document visible conditions; a qualified drainage contractor or engineer can evaluate the remedy when grading, soil, or persistent water problems need more than a simple maintenance review.
Does this only matter with a basement?
No. Roof runoff and ground slope also matter around crawl spaces and slab foundations, although the details differ. The basement drawing makes the concept easier to see.
Do gutters guarantee a dry basement?
No. They manage roof water, not every moisture source. Groundwater, drainage systems, cracks, plumbing, and condensation may need separate evaluation.
Should I pile soil against the wall?
Do not bury siding, vents, weep holes, or other required clearances to create a slope. Get site-specific advice before regrading or changing buried drainage.
Further reading: Building America: final grading · Building America: gutters and downspouts.
Foundation clues · Crawl-space questions · Back to Learning Hub.
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