Gutters Catch It, Downspouts Decide Where It Goes
A flawless gutter installation that catches every drop of rain is wasted if the downspouts dump that water directly at the base of your foundation. The gutter's job is to capture water off the roof; the downspout's job is to move it safely away from the home.
When downspouts discharge at the foundation wall, all that roof water pools against the footing. Over a wet Western Washington winter, that constant saturation erodes soil, seeps into basements and crawlspaces, and stresses the foundation wall.
Why 4 Feet Matters
Building best practice and our field experience both point to discharging downspout water at least 4 feet from the foundation. Less than that, and the saturated soil zone extends back under the footing. More is better on sloped lots or homes with basements.
This is achieved with either surface extensions (rigid or fold-up) that carry water out along the ground, or buried drainage lines that route it to a pop-up emitter or French drain downhill.
Choosing the Right Discharge Method
The best method depends on your lot's slope, soil, and where the water can safely go:
- Splash blocks — the minimum, deflecting water a foot or two from the downspout exit. Fine for small roofs on well-drained lots.
- Surface extensions — rigid PVC or aluminum, or hinged fold-up styles, carrying water 4+ feet out. Affordable and visible, so clogs are obvious.
- Buried drainage lines — underground pipe routing water to a pop-up emitter or dry well. Cleaner look, ideal for finished landscaping, but needs proper slope to avoid clogging.
- French drains — gravel-filled trenches for high-volume lots or areas where surface discharge isn't possible.
Sizing the Downspout to Match the Gutter
Even the best extension can't help if the downspout itself is undersized. Standard 2x3-inch downspouts back up during atmospheric river storms. We recommend 3x4-inch downspouts on seamless 6-inch gutters — the larger opening moves water fast and resists clogging with pine needles and fir cones.
Pair the right downspout size with a 4-foot discharge and your roof-to-ground drainage system actually completes its job: water off the roof, into the gutter, down the downspout, and away from the foundation.
