The Downspout Is the Problem: How Roof Water Ends Up Against Your Foundation

Walk around your house during the next storm with an umbrella and watch the bottom of each downspout. If water is pouring onto a splash block, running across the mulch and pooling against the slab, you have found the cause of at least half of the wet-yard problems we see — before anyone mentions the words French drain.

What a downspout actually delivers

Gutters concentrate the entire roof into a handful of pipes. A single downspout can carry the rain from 400 to 600 square feet of roof. In a Jacksonville summer storm — 2 inches in an hour is normal — that is a garden hose running full for the whole storm, aimed at one square yard of soil beside the foundation. Sand over hardpan cannot absorb that rate, so the water spreads along the wall, finds the lowest bed and sits.

Signs the downspouts are the problem

• The wettest spot is within six feet of the house, usually at a corner.
• Mulch washes out of the bed at the same place every storm.
• There is a dark stain or green algae line on the stucco or block near the ground.
• The lawn is wet near the house and dry at the fence — if it were the lot, it would be the other way around.
• Puddles form on the patio or the pool deck right where a downspout empties.

Why the splash block is not enough

A splash block moves the water about 18 inches. On a lot with any slope back toward the house — and settling makes that common — the water simply returns. A flexible plastic extension helps until the mower hits it. Neither does anything about the fact that the soil beside the foundation is receiving a roof's worth of water every storm.

Underground downspout drainage

The fix we install most often is simple: each downspout is connected at the base to a solid (not perforated) pipe, buried below the sod, which carries the water to a legal discharge point — a pop-up emitter at the curb, a swale, a dry well, or the yard's French drain system. The pipe is solid because the goal is to carry water away, not to let it soak in beside the house. Cleanouts go at the turns so oak leaves and roof grit can be flushed out.

In our area this runs $300 to $800 per downspout depending on the distance to the outlet and what is in the way (a driveway or a paver walk means a bore or a cut). A typical house with four points is $1,500 to $3,000, and it is often the whole fix.

What it is not

Downspout drainage does not fix a lawn that floods in the middle of the lot — that is a grading or French drain job — and it does not fix gutters that overflow because they are clogged or undersized. We check both on the inspection. If the gutter is dumping over the edge, the downspout never sees the water.

Where the water goes matters

Florida does not allow you to send your roof water onto a neighbor's lot, and a downspout line that pops up at the property line is exactly that. We route to the street, a swale on your own lot or a dry well, and we put the discharge point on the drawing you sign. Free inspection within 48 hours: (904) 561-1816.