How to Install a French Drain Outside With Concrete

Drainage outdoors can be just as important as drainage within a structure. Water left to drain naturally may make its way into your structure’s foundation, weakening it, or it can collect in pools, stagnating and potentially causing health hazards or destroying landscaping. Installing a French drain can help you direct water away from structures or manicured landscapes. Making the drain with concrete that rests on the grounds surface is a quick way to create French drains, as it alleviates the need for digging deep trenches and laying pipe with gravel for, as is necessary for underground French drainage systems.

Landscaping paint
Spade
Tamp
Concrete mix
Wheelbarrow
Exact angle inside corner trowel

Instructions

- 1
  Mark a line on the ground where you wish to run the length of the French drain with landscaping paint. You’ll want your drain to follow a path downward, away from any structures, with the end of the drain emptying into a gutter or a large field. Make certain that the path has a slope of at least 1/8-inch per foot of drainage length.
- 2
  Dig a trench along the marked location with a spade. Make the depth of the trench about 4 inches to prevent the drain from cracking with shifts in soil, and the width 8 inches. Maintain a downward slope along the drain of at least the 1/8-inch per foot rate.
- 3
  Tamp the trench with a tamper to compress the soil, creating as solid a base for the drain as possible.
- 4
  Mix the concrete for the drain in a wheelbarrow, adding enough water to create a mixture with the consistency of thick pancake batter. Use a spade to incorporate the water into the dry mix, folding the mix from the center bottom of the wheelbarrow to the top to work the water throughout.
- 5
  Fill the trench with the concrete to the level of the surrounding soil.
- 6
  Adjust an exact angle inside corner trowel to about a 150-degree angle. Run the trowel through the center of the concrete, creating a V-shaped notch in the length of the trench to make the concrete into a French drain. Keep the depth of the notch to 1/4-inch or less to maintain water movement while preventing standing water during winter that it can freeze before draining out completely.
- 7
  Allow the drain to dry for 21 days. Keep the surface damp for the first 3 days after pouring to prevent a brittle finish.

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