How deep should a French drain be?

Deep enough to intercept the water causing the problem and to maintain fall to the outfall. A yard drain may only need eighteen inches; a footing drain has to sit at footing level. Depth is set by the outfall, not by a rule of thumb.

How much slope does a French drain need?

About one percent — roughly one inch of drop per eight to ten feet — is a reliable minimum. Less than that and silt settles out inside the pipe.

Where does the water actually go?

To daylight wherever grade allows, since gravity outfalls need no maintenance. Where there is no fall, a sump and pump or a properly sized dry well is the alternative.

Do French drains fail?

The ones without filter fabric, without fall or without an outlet do. Installed correctly with cleanouts, they run for decades with a periodic flush.

Water first

French Drain Installation & Subsurface Drainage in North Georgia

French drains, curtain drains and downspout tie-ins that pull groundwater away from foundations, yards and barns on clay soils.

A French drain is simple to describe and easy to build wrong. Fabric, stone, pipe, slope and an outfall all have to be right, or you have installed an expensive underground sponge. We install subsurface drainage that has somewhere to go and stays clear for decades.

Part of our Drainage & Erosion Control in North Georgia work across North Georgia.

What we see most often

Soggy yard that never dries out between rains
Water in a crawlspace, basement or against a foundation wall
Existing drains that were installed with no fall or no outlet
Pipe silted shut because it was laid without filter fabric

Scope of work

What this work includes

Source & soil assessment

Identifying whether the problem is surface runoff, a seep, a high water table or a downspout before choosing a system.

Curtain & interceptor drains

Trenched drains upslope of the wet area that cut off subsurface flow before it reaches the structure or yard.

Footing & foundation drains

Perforated pipe, washed stone and filter fabric at footing level, tied to a gravity outfall or sump.

Outfall & cleanouts

A daylight outlet with an animal guard, plus cleanouts so the system can be flushed instead of dug up.

Dry ground, a dry foundation, and a system you can flush instead of excavate.

How it goes

Our process

Step 01
Diagnose
Confirm the water source before specifying any pipe.
Step 02
Design fall
Establish the outfall elevation first, then work back uphill.
Step 03
Install
Fabric, washed stone, perforated pipe, correct bedding.
Step 04
Verify
Flow test the line and restore the surface.

Common questions

French Drains questions we get

How deep should a French drain be?: Deep enough to intercept the water causing the problem and to maintain fall to the outfall. A yard drain may only need eighteen inches; a footing drain has to sit at footing level. Depth is set by the outfall, not by a rule of thumb.
How much slope does a French drain need?: About one percent — roughly one inch of drop per eight to ten feet — is a reliable minimum. Less than that and silt settles out inside the pipe.
Where does the water actually go?: To daylight wherever grade allows, since gravity outfalls need no maintenance. Where there is no fall, a sump and pump or a properly sized dry well is the alternative.
Do French drains fail?: The ones without filter fabric, without fall or without an outlet do. Installed correctly with cleanouts, they run for decades with a periodic flush.

Where we work

Drainage & Erosion across North Georgia

We handle drainage & erosion for property owners across the north side of Atlanta — Cumming, Milton, Alpharetta, Roswell, Buckhead, Sandy Springs, Marietta, Woodstock, Canton and Ball Ground — and up through Jasper, Ellijay and Blue Ridge. Choose your area for local conditions, permitting and recent work nearby.

Regional overviews: Drainage & Erosion in North Georgia, Drainage & Erosion in Lake Lanier, Drainage & Erosion in North Georgia Mountains, Drainage & Erosion in North Atlanta.

Also serving Milton, Dahlonega.

Related work

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French Drain Installation & Subsurface Drainage in North Georgia

What we see most often

What this work includes

Source & soil assessment

Curtain & interceptor drains

Footing & foundation drains

Outfall & cleanouts

Our process

Diagnose

Design fall

Install

Verify

French Drains questions we get

Drainage & Erosion across North Georgia

Erosion Control

Culverts & Basins

Foundation Regrading

Tell us about your property