What Is a French Drain?
A French drain is a subsurface drainage system designed to intercept and redirect groundwater or surface water before it accumulates near your foundation. It typically consists of a sloped trench filled with gravel and a perforated pipe, which collects water and carries it to a discharge point away from the home.
Despite the name, there's nothing particularly French about them — the term comes from Henry Flagg French, a 19th-century American farmer and drainage expert who popularized the system.
How French Drains Help Prevent Basement Water Problems
If water is consistently pooling near your foundation after rain, or if your yard slopes toward your house rather than away from it, a French drain can intercept that water before it reaches your basement walls. It's often part of a broader exterior water management strategy that may also include grading corrections and downspout extensions.
Interior vs. Exterior French Drains
French drains can also be installed on the interior perimeter of a basement — this is essentially what most interior waterproofing drainage systems are. Interior systems collect water that enters through the walls or floor and route it to a sump pump. Exterior French drains intercept water in the soil before it reaches the wall.
The right approach depends on the source and volume of water, the soil conditions, and what's practically achievable at the property. We'll walk through the options with you.
South Coast MA Soil Considerations
The soil throughout Dartmouth, Westport, Acushnet, and much of Bristol County includes a significant amount of clay, which drains poorly and holds moisture around foundations. This is one reason French drains and proper exterior grading are particularly valuable in our region.
What a French Drain Installation Involves
- Site evaluation to determine water flow patterns and outlet options
- Trenching at the appropriate slope (typically 1% grade or more)
- Gravel bed and perforated pipe installation
- Geotextile fabric to prevent soil intrusion and clogging
- Proper outlet to daylight, a dry well, or municipal drainage as appropriate
- Site restoration