Foundation Drainage Systems

Most basement water problems are drainage problems. Water accumulates in the soil around the foundation, raises the local water table, and pushes against the structure. A waterproofing membrane resists that water, but a drainage system removes it — and the two work best together.

A perimeter drainage system collects water before it reaches the wall: a drain at the footing, surrounded by washed gravel and wrapped in filter fabric so the drain stays open, graded to a sump or discharge point. The ground surface is then shaped to fall away from the building, and roof water is taken away in gutters and downpipes.

The detail most often missed is the filter. A drain surrounded by soil silts up within a season or two; a drain surrounded by graded aggregate and a geotextile keeps working. The discharge point matters too — a drain that empties next to the foundation just moves the problem.

Where the structure is already built, retrofit drainage is constrained but not impossible. It may mean a French drain at the perimeter, a sump and pump, or redirecting roof water — and it is often cheaper than excavating to renew a membrane.

Drainage needs maintenance. Sumps, outlets and channel drains block, and a system that is not checked before the rainy season will eventually back up. We hand over the layout and the maintenance points so the system keeps working.