Roof runoff is concentrated water. When it falls from the roof edge or pours out of a downspout onto bare soil, it digs trenches, washes out beds and exposes the foundation.
Controlling where roof water lands stops the erosion.
What you may be seeing
- A trench along the drip line
- Mulch and soil washed onto walkways
- Holes at downspout outlets
- Exposed roots or slab edge
- Splash marks on siding
First question: does the house have gutters where the erosion is?
No gutters means water falls straight onto the soil. With gutters, check for overflow or a downspout discharging there.
If there are no gutters
Water sheets off the roof edge onto the soil.
Possible causes:
- No gutters
- Roof valley concentrating flow
If gutters overflow
Water spills over the gutter in heavy rain.
Possible causes:
- Clogged gutters
- Undersized gutters or too few downspouts
If erosion is at a downspout outlet
Water exits with enough force to move soil.
Possible causes:
- No splash block or extension
- Discharge onto a slope
What you can check yourself
Only check these safely and after rain has stopped. Do not dig near marked utilities, and do not go near electrical equipment that is standing in water.
- Watch the roof edge in rain
- Clean the gutters and check for overflow
- Look for valleys above the erosion
- Check downspout outlets
Answer 20 quick questions → to get a preliminary drainage assessment.
What a drainage professional may evaluate
- Roof drainage review
- Downspout routing
- Grade restoration plan
- Erosion control options
Most common causes
No gutters
Roof water falls straight on the soil.
Overflowing gutters
Debris or undersizing.
Valleys
Concentrated flow at one point.
Unprotected outlets
Downspouts onto bare soil.
Possible solutions
The right fix depends on where the water comes from, where it collects and where it can legally and physically go. These are the solutions most often considered:
Gutters and downspouts
Capture roof water.
Underground downspout drainage
Carry water away.
Drip-line protection
Rock or plantings where water falls.
Soil restoration
Rebuild and regrade the eroded area.
When to call a drainage professional
- The foundation is exposed
- Erosion keeps returning
- Gutters overflow even when clean
Frequently asked questions
Do I need gutters on my house?
Where roof water is causing erosion or pooling at the foundation, gutters with downspouts discharging away from the house are usually recommended.
Is rock under the drip line enough?
Rock protects the soil from splashing but doesn't move the water away. Combine it with grading or drainage.
Bottom line
Control where roof water lands and the erosion stops.
This page is educational and does not replace an onsite evaluation. Conditions, codes and HOA rules vary by property.