How to Install French Drains Around a Foundation
If soil drainage is poor, water can build up around a foundation and, over many years, cause the foundation to move, crack or start to disintegrate. Adding French drains around the perimeter of the foundation helps to divert excess standing water away from the foundation, effectively lengthening the time the foundation will be sturdy. French drains can be hand-dug, but a small backhoe (you can rent these) will make the work go much faster.
Dig trenches about 2 feet wide and 2 feet deep around the perimeter of the foundation. If the outside wall is less than 16 feet, one trench will suffice. If the wall is more than 16 feet, dig 2 trenches along the wall. The trenches should be at least 4 feet long. The more clay the soil has, the longer the drains should be because clay does not drain well. When the drains become full, the water may back up against the foundation if the drains are not long enough.
Layer 12 inches of the 1-inch stone at the bottom of each trench. Layer 6 inches of gravel over the stone. Pack the gravel onto the stone---you can simply stomp on the gravel with your feet or hit it with the end of a board. It does not need to be packed hard--just enough to get the gravel to settle.
Layer 4 inches of sand on top of the gravel. Layer the sand 1 inch at a time, so that it falls through the gravel. Pack the sand with the end of a board or with your feet.
Lay 2 inches of topsoil on top of the sand. Lightly pack the top soil with your feet (just walk on it, there is no need to stomp it). Layer sod on top of the topsoil.
Water the sod. When it rains, the water will go through the drains, as the combination of stone, sand and gravel will allow the water to drain out and away from the foundation.
Things You Will Need
- 1-inch stone
- Top soil
- One cubic foot is 3 feet times 3 feet time 3 feet. Stone, gravel and sand is usually sold by the cubic foot.