How to Install Rigid Insulation Around a French Drain
- 1). Install rigid insulation around an existing French drain on a dry day. Do not attempt to install the insulation within two days of rain.
- 2). Remove as many of the components of the French drain as possible. Use a spade to cut around the sod over the top of a French drain, if the drain is sod-covered, or pick out the rocks that line the surface of the drain. Place the rocks into containers of water to rinse them clean as you work on the rest of the drain.
- 3). Dig up the coarse sand that makes up the next layer of the French drain. Be careful against the sides of the drain if you have used landscape fabric in the drain’s trench to keep from tearing holes in the fabric. Place the sand in a container for reuse.
- 4). Pick the rocks from the bottom of the French drain, below the sand. Once you have removed all of the rocks, pull the landscape fabric, if you used it, carefully from the French drain by the sides to get any coarse sand caught in the fabric. Dump the sand into a container.
- 5). Put the landscape fabric back if it has no holes. If the fabric has developed holes, cut a new piece of landscape fabric wide enough to line the drain for 1 to 2 inches of fabric coming out the top of the trench on each side.
- 6). Clean the wall of a home or building’s foundation, if the French drain lies alongside the structure, with a cleaning brush and water to remove dirt from the wall. Line the foundation with waterproof sheeting if it’s not already lined. To install sheeting, cut the sheeting down to the length of the wall, peel off the backing and press the adhesive side against the clean wall.
- 7). Place the rigid insulation boards along the foundation of a structure or just along the sides of the trench over the landscape fabric if you want to line a French drain that doesn’t sit against a structure. Return the layers of the French drain to their places, spreading rocks, then sand, and covering the trench with rocks or sod.