French Drain vs Gutters: Which One Protects Your Foundation?

When water stands against the foundation after every storm, homeowners usually hear two different sales pitches: one company sells gutters, the other sells a French drain. Both can be right, and both can be wasted money, depending on where the water comes from. On a Jacksonville house the order matters — and the cheaper fix usually comes first.

Where the water against your foundation comes from

There are two sources, and they behave differently.

• Roof water. A roof gathers a lot of rain into a few places. Every inch on a 2,000 square foot roof is more than a thousand gallons, and Jacksonville storms drop 2 to 4 inches at a time. Without gutters it pours off the eaves along the whole wall; with gutters and short downspouts it lands on a splash block about 18 inches from the slab.
• Ground water moving sideways. Rain soaks into the sand, stops on the hardpan 12 to 36 inches down and runs sideways toward the lowest point. If the lot slopes toward the house, or a neighbor's lot sits higher, that water arrives at your foundation from below the surface.

What gutters fix

Gutters collect the roof water before it hits the ground and deliver it to a few downspouts. That is half of the job. The other half is getting the water away from those downspouts — extending them or piping them underground to the street, a swale or a dry well. Gutters that end on splash blocks just move the problem from the whole wall to a few corners. Gutters that overflow because they are clogged or undersized dump the roof at the wall no matter where the downspout ends.

What a French drain fixes

A French drain — perforated pipe in washed gravel and filter fabric — collects water moving along the hardpan and carries it to an outlet. It is the fix for the second source: a wet strip along the side yard, a neighbor's runoff, water that stays after the surface has dried. A French drain does nothing about a roof that is dumping its water at the wall; if you build one next to a downspout that empties on a splash block, the drain spends every storm carrying roof water it should never have received.

Which comes first

1. Check the gutters. Are there gutters on the side that floods? Do they overflow in a storm? Are there enough downspouts for the roof — each one handles roughly 400 to 600 square feet?
2. Check where the downspouts end. If the wettest spot is within six feet of the house, usually at a corner, the downspouts are the prime suspect.
3. Pipe the downspouts away. Underground lines to a legal outlet are the cheapest drainage fix we sell, and on many houses the whole fix.
4. Then judge the yard. If water still stands 48 hours after a storm, or the lawn squishes along a line, the ground water needs a French drain or regrading.

When you need both

On a lot that settled toward the house, or one that takes a neighbor's runoff, the roof and the ground are both delivering water to the foundation. Then the honest plan has both: gutters and downspouts piped away, and a French drain or a regraded swale for the ground water — often sharing the same outlet line.

Signs you need both

• The wet strip by the wall dries once the downspouts are piped away, but the middle of the lawn still holds water 48 hours after a storm.
• Water arrives from the neighbor's side of the lot even on days your roof barely drains.
• The soil beside the slab stays soft after the surface has dried — water is moving on the hardpan, not off the roof.

What each costs

Seamless gutters run $6 to $12 per foot installed in our area; a one-story house with 150 to 200 feet of gutter is about $900 to $2,400. Downspouts piped underground are $300 to $800 each. A French drain is $20 to $45 per foot, with a typical 50 to 100 foot run at $2,000 to $6,000. Rough out your house with the gutter cost calculator or the French drain cost calculator.

The inspection is free and covers both — gutters, downspouts and the grade — before anyone prices a drain. See gutters & downspout extensions and French drain installation, or call (904) 561-1816.