Though mistakenly referred to as "French Drains," exterior
perimeter foundation drains are designed to collect the water that
accumulates next to the foundation wall and divert the water away from the
home. Clay drainage tiles in older homes or perforated plastic
drainage tiles in new
homes are placed next to the foundation footer and covered with a minimum of
6 inches of gravel or crushed stone. The surface water that enters the
soil next to the foundation flows down the wall, then following the path
of least resistance, flows through the gravel and into the drainage tile
or pipe. The water is then directed to either a storm sewer, dry well
or, if necessary, to a sump pump to be directed away from the home.
Generally, the system is only placed next to the one or two walls that experience
the water penetration problems. However, in some severe cases, the
system is placed around the entire perimeter. In addition, to help
prevent sediment from entering and clogging the drain pipe or tile, a filter
paper is placed around the pipe (especially the openings) or gravel.
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Crawlspaces
Basements
Sources of Water Penetration Dealing
with Water Penetration
Surface Water Control
Gutters
and Downspouts Surface Grading
Interior Perimeter Drain
Drain Tile
Trenches and Sump Pump
Vapor Barrier
and Vents
