Drainage + Grading Around Foundation Reference

Why this matters

A surprisingly large percentage of "foundation problems" + "basement leaks" + "termite issues" trace back to poor drainage around the foundation. Water that should run away from the house instead sits at the base, soaking the soil, undermining footings, attracting pests, and entering through cracks. The tech who recognizes drainage failure helps customers solve root causes - often dramatically cheaper than the symptoms being chased. This is the field card.

The basic rule

Water must move AWAY from the foundation, not toward it OR sit at it.

• Grade slopes down + away from the house
• Downspouts discharge well away from foundation
• Surface water doesn't pool at the base
• Soil at foundation isn't saturated

Violation of this rule causes:

• Wet basements + crawlspaces
• Foundation settlement / heaving
• Mold + mildew
• Termite + carpenter ant attraction
• Wood rot at sill plate
• Driveway + sidewalk cracking

Foundation grading

Grade = the slope of the soil surface near the foundation.

Proper grade:

• Soil slopes down + away from foundation
• IRC requires 6 inches of drop in the first 10 feet
• (Some local codes: 5% slope = roughly the same)
• Continues for at least 10 ft away from foundation

Bad grade indicators:

• Soil sloping toward house
• Flat / level area at foundation
• Negative pitch (water flows in toward house)
• Sunken areas creating pools
• Erosion gullies

Causes of bad grade:

• Original construction skipped grading
• Settlement over time (soil compacts)
• Landscaping additions raised the grade
• Erosion lowered the grade

Downspouts + roof drainage

Roofs collect tremendous water; downspouts discharge it. Where they discharge matters.

Discharge location:

• Minimum 5 ft from foundation (10 ft+ better)
• Onto sloping ground that continues away
• NOT into a flower bed at the base
• NOT into a 1-ft extension that ends right next to the foundation

Downspout extensions:

• Splash blocks: 3 ft typical; minimal help
• Aluminum / vinyl extensions: 5-10 ft; mid-tier
• Underground drainage pipe: extends to daylight OR storm sewer; best for severe sites

Roof + gutter capacity:

• Standard 5" K-style gutter handles most residential rainfall
• Heavy storms may overwhelm; overflow at gutters = water at foundation
• Larger gutters (6"+) OR more downspouts for high-rainfall areas

Surface water

Beyond roof water, surface water from:

• Neighboring property runoff
• Hillside above the home
• Driveway / sidewalk drainage
• Roof valleys concentrating water

Surface water solutions:

• Swale (shallow grass-lined ditch) directs water around
• French drain (gravel + perforated pipe underground) collects + directs
• Catch basin at low points
• Diversion berm uphill of the house

French drain basics

A French drain:

• Trench at the problem area
• Perforated pipe at bottom
• Filter fabric (geotextile) around gravel to prevent silt blocking pipe
• Gravel fills trench
• Catches groundwater + surface water
• Pipe daylights downhill OR connects to storm system

Typical residential French drain:

• 12-24" deep
• 12-18" wide
• 4" perforated pipe (corrugated OR rigid)
• Holes facing down (so water enters from groundwater)
• Sloped 1-2% toward outlet

Footing drains

Footing drain (foundation drain) installed at original construction OR as remediation:

• Pipe at base of foundation footing
• Drains groundwater pressure away
• Connects to storm OR daylight
• Critical for basements in wet soils

If basement leaks: footing drain may be missing, blocked, OR damaged.

Window wells

Below-grade basement windows often in window wells:

Proper window wells:

• Lined with gravel
• French drain at the bottom OR connection to footing drain
• Cover (perforated for ventilation, blocks debris)

Failed window wells:

• Fill with water
• Water flows in through window
• Snow melt in winter is the worst

Window well failure is a common basement water entry point.

Common drainage failures

Downspout dumping at foundation:

• The most-common cause of wet basements
• Downspout cut off short; water pools at footing
• Cure: extension OR underground drain

Negative slope:

• Soil grade slopes toward foundation
• Easy fix: add soil to build up grade
• Compact + slope away

Flower bed against foundation:

• Mulch + soil higher than original grade
• Creates negative slope OR trap
• Solution: remove bed OR lower; install drain

Driveway / sidewalk pitched wrong:

• Concrete settled; now slopes toward house
• Repair: mudjack to lift OR re-pour
• More expensive than soil grading

Sprinkler too close to foundation:

• Sprinkler aimed at landscaping next to house
• Wets the foundation continuously
• Adjust spray pattern OR remove

Air conditioner condensate at foundation:

• AC drain dumps right at foundation
• Add hose to extend away

Gutters undersized:

• Heavy rain overflows
• Even with good downspouts, overflow at foundation
• Larger gutters OR more downspouts

Disconnected downspout:

• Joint broken; downspout dumps before reaching ground
• Water down siding into foundation
• Easy fix

Visible water entry signs

In basement:

• Damp walls
• Efflorescence (white powdery mineral deposits)
• Mold / mildew smell
• Visible water during / after rain
• Damp floor near walls
• Standing water at low spots

At foundation exterior:

• Wet soil + grass adjacent to foundation
• Erosion gullies
• Settling near foundation
• Algae / moss growth on wall (sustained moisture)

On floors above:

• Cupping wood floors (over basement)
• Damp baseboards
• Musty smell on cold mornings

Cross-trade observations

HVAC tech:

• AC condensate drain location (foundation = problem)
• Furnace cabinet rust at base (water on floor from leak above)
• Duct condensation in crawlspace (humid environment = drainage issue)

Plumber:

• Basement leak that's not from a plumbing fixture
• Sump pump operation (running often = high water table)
• Old crawlspace with damp walls

Roofer:

• Gutters / downspouts (your installation point)
• Roof water management is roofer's responsibility on a new roof

Pest control:

• Termite damage at sill plate (wet wood)
• Carpenter ants in moist areas
• Mice / rodents in damp crawlspace
• Mosquito breeding in standing water

Landscaper:

• Mulch + soil heights against foundation
• Sprinkler placement
• Garden bed slopes

Diagnostic walk-around

When customer reports basement OR foundation water issue:

1. Walk around foundation perimeter:

• Note grading
• Identify low spots
• Check downspout discharge points
• Look for erosion

1. Check gutters during rain (if possible):

• Overflowing?
• Disconnected?
• Clogged?

1. Check basement during / after rain:

• Water location
• Path it took from outside to inside
• Wet wall vs wet floor

References

• IRC Chapter 4 (Foundations) - grading + drainage requirements
• ASCE 32 (Frost Protected Shallow Foundations)
• AWWA + local stormwater management codes
• Manuall internal: Foundation Problem Signs, Drainage + Grading Principles