French Drain
Installation
in Maryland

A French drain is a sloped trench filled with gravel and a perforated pipe that collects groundwater and moves it in a controlled direction, typically to daylight at a lower elevation, into a dry well, or to a sump basin. The principle is simple: give water a lower-resistance path than the one through your foundation wall.

In Maryland's Piedmont region, which covers most of Baltimore, Harford, Carroll, and Cecil counties, the native soil is a dense, finely grained clay with poor drainage. French drains here need the trench deeper than the frost line, 24 to 30 inches, clean gravel free of fine material that would clog over time, and the pipe wrapped in filter fabric to prevent clay infiltration. A French drain installed without these considerations fails within a few seasons.

An exterior French drain placed at footing depth is the most effective way to relieve hydrostatic pressure, since it intercepts groundwater before it contacts the wall. Interior drainage systems manage water that has already entered the foundation. For foundations with active wall cracks driven by exterior water pressure, OBW recommends addressing the exterior first. Where excavating around the full perimeter isn't practical, dense landscaping, proximity to neighboring structures, or finished garage floors, interior drainage is the appropriate solution. We assess your specific site conditions and recommend the right combination, not just the easiest job to sell.

OBW excavates along the foundation or at the affected grade, lays a continuous bed of 57-stone gravel, sets 4-inch perforated pipe wrapped in filter sock, and backfills with clean stone to within 6 to 8 inches of grade. We finish with a weed barrier fabric and topsoil, and connect the outfall to a proper daylight discharge point or sump inlet. Downspout leaders and surface water sources are addressed as part of the same project where relevant.

Water pooling in your yard for days after rain, particularly near the foundation. Soil along one side of your home staying visibly wet longer than other areas. Basement wall cracks with water staining that correlates with rainfall. Downspouts discharging at grade with no runoff path. Neighbors uphill adding drainage that redirects water toward your property. A landscaping project that changed the grading so water now flows toward the foundation instead of away.

The trench has to sit below the frost line, 24 to 30 inches in Maryland, or freeze-thaw cycling will disturb the pipe and gravel bed over successive winters. A drain that's too shallow also intercepts less of the groundwater actually moving toward the foundation at footing depth. Every French drain OBW installs is backed by a written workmanship guarantee, terms vary by service, ask your inspector.