In most homes, an external French drain or drain tile is installed around the foundation walls before the foundation soil is backfilled. It is laid on the bottom of the excavated area, and a layer of stone is laid on top.
Once the drain is installed, the area is backfilled and the system is left alone unless it clogs.
Once completed, the area, save for a 2 in (5.1 cm) gap around the edge, is concreted over. This gap exists to allow water in from the foundation walls. This can be installed very quickly—one to two days by an experienced crew. The system is easy to maintain once installed.