French Drain System
What is a French Drain and how does it work?
My neighbor told me I need a french drain installed around the outside of my house to move water away,
or I was going to need expensive foundation repairs. What is a french drain, and how does it work?
French drain installations move water away from your home with a trench that
collects ground water and moves it away from your homes foundation. We recently
installed an8 inch wide,and 30 inch deep french drain for 250 feet along all three
sides of a house in Denver that was experiencing problems with wet basement walls,
sump pumps, and foundation problems.
We first locate the problem areas; usually an area of the ground that does not slope properly
away from the existing foundation. French drains are rarely needed around the entire house,
except in extreme cases.
We'll then decide where we want the water to go so it doesn't affect your neighbors
house, especially in Denver with our heavy clay soils. French drains can work even when
they're level if built correctly, but slopes of 4-6 inches per 50-100 feet will function the best.
Trenches for french drains should be at least 6-12 inches wide, and usually 20-30 inches
deep in most areas, and will run along the wall of your house that's causing you the problem.
We then place a 3-6 inch layer of gravel in the bottom of the trench, and lay a 4 inch sock
lined perforated pipe on the gravel. Then we place our geotext fabric over the perforated pipe
and then add another 4 inch layer of gravel before placing whatever the customer wants as
the new ground cover.
These two properties had been experiencing negative drainage to the center of their property lines for years. Water pooling, saturated lawns and the bugs made it impossible to go outside. Alpine chose to use the natural look of river rock as the border between the properties and installed the french drain under the grass.