How to Place Splash Blocks Under Downspouts
Water pours straight out of your downspouts and pools right against the foundation, eroding the soil and risking moisture in the basement or crawlspace. A splash block redirects that flow away from the house.
A splash block is a simple concrete or plastic trough placed at the bottom of a downspout. It catches the concentrated stream of roof runoff and spreads it out, carrying it a short distance away from the foundation so the water doesn't dig a hole at the corner of the house or soak into the soil against the wall. Effectiveness comes down to two things: the block has to slope away from the house so gravity carries water outward, and the ground beyond it needs to keep draining away too. It's an easy, effective defense against foundation moisture problems.
How the job is done
- 1
Clear and grade the spot
The area under the downspout is cleared of debris and the soil is shaped so the ground slopes gently away from the foundation, giving the block a base that drains outward.
- 2
Set the block under the downspout
The splash block is positioned with its high, wide end directly beneath the downspout outlet so the falling water lands in the trough rather than beside it.
- 3
Pitch it away from the house
The block is tilted so its outlet end sits lower and points away from the foundation, and it is checked to confirm water will run toward the yard, not back toward the wall.
- 4
Seat it firmly so it stays put
The block is bedded into the soil so it doesn't rock, shift, or get knocked out of alignment by mowing or heavy rain.
- 5
Test with running water
Water is run through the downspout, or the next rain is observed, to confirm the flow lands in the block and drains away from the house as intended.
What a pro checks
- Grades the soil so it slopes away from the foundation under the block
- Aligns the wide end directly beneath the downspout outlet
- Pitches the block downhill so water runs toward the yard
- Beds the block firmly so it won't shift or rock loose
- Considers a longer extension where runoff is heavy or soil is flat
- Confirms drainage by testing with water rather than assuming
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Frequently asked questions
How far from the house should the water end up?
The goal is to move runoff far enough that it doesn't pool against the foundation. A splash block handles a short distance; for heavy flow or flat ground, a downspout extension carries it farther out.
Is a splash block enough, or do I need an extension?
A splash block works for many homes, but if water still collects near the foundation, a downspout extension or buried drain line that discharges well away from the house is the stronger solution.
Why does water still pool by my foundation with a block in place?
Usually the block is level or tilted the wrong way, or the surrounding ground slopes back toward the house. Re-grade the soil to fall away and pitch the block so its outlet sits lower.
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