A drainage system installed around the foundation perimeter to collect and redirect groundwater away from building structures.

A perimeter drain is a drainage system installed around the foundation perimeter of a building to collect and redirect groundwater away from the structure, preventing water infiltration into basements, crawl spaces, and foundation walls. This subsurface drainage system typically consists of perforated pipes surrounded by gravel or aggregate that intercepts groundwater before it can reach the foundation and channels it to a safe discharge point such as a storm sewer, daylight outlet, or sump pump system. Perimeter drains are essential components of foundation waterproofing systems that help maintain dry interior conditions, prevent structural damage from hydrostatic pressure, and protect building materials from moisture-related deterioration.

Perimeter drains are installed in various configurations and applications including exterior foundation drains placed outside the foundation wall at or below the footing level to intercept groundwater before it reaches the structure, interior perimeter drains installed inside basement or crawl space floors that collect water that has already penetrated the foundation system, French drains that use similar principles for surface and subsurface water management in landscaping and site drainage, curtain drains installed uphill from structures to intercept groundwater flow before it reaches the building area, and specialty applications such as retaining wall drainage, sports field drainage, and agricultural drainage systems. Each application requires specific design considerations based on soil conditions, groundwater levels, and site topography.

The components and construction of perimeter drain systems include perforated drain pipes typically made from PVC, corrugated polyethylene, or clay tile that allow water entry while maintaining structural integrity, filter fabric or geotextile wrapping that prevents soil particles from clogging the pipe perforations, gravel or aggregate bedding that provides a free-draining medium around the pipe and facilitates water collection, backfill materials that restore proper grading while maintaining drainage function, and outlet systems that safely discharge collected water away from the foundation. Additional components may include inspection ports, cleanouts, and connection to sump pump systems where gravity drainage is not feasible.

Fun Fact: The concept of perimeter drainage dates back to ancient civilizations, with Roman engineers using clay pipes and stone channels around building foundations over 2,000 years ago, establishing principles still used in modern foundation drainage systems.

• Area Drain
• Foundation Drain
• French Drain