French Drain
French Drain
(OP)
I have daylight ranch style home, and the front yard slopes down approximately 10-15 feet for 30-40 feet before it reaches the front of my foundation at the front bedroom wing and front porch. During heavy rains (frequent in the NW) water pools near the front of my foundation and front porch. I have begun to research french drains, but have received conflicting advise. At this point, I am planning on digging a trench filled with a 2" gravel base, 4" perforated drain pipe, and covered with additional gravel, landscape fabric, and topsoil. The drain will slope to the side of the house, and then down the hill parrallel with the home and daylight below.
My main questions include
(1)How deep and wide to dig the trench,
(2)How far from my front foundation to locate the trench/drainpipe?
(3)Wether to install additional drainage improvements at the base of the hill higher up on the lot and furtehr from the house?
Some Points worth noting:
(A)The home was built in 1979
(B)The foundation at the front of the house is shallow (1.5 ft deep, but there is a deep concrete retaining wall further back on the house.
(c)The soils appear to have a heavy content of clay
of my home is located below street grade and the lot hillside
Any advise would be really appreciated!
My main questions include
(1)How deep and wide to dig the trench,
(2)How far from my front foundation to locate the trench/drainpipe?
(3)Wether to install additional drainage improvements at the base of the hill higher up on the lot and furtehr from the house?
Some Points worth noting:
(A)The home was built in 1979
(B)The foundation at the front of the house is shallow (1.5 ft deep, but there is a deep concrete retaining wall further back on the house.
(c)The soils appear to have a heavy content of clay
of my home is located below street grade and the lot hillside
Any advise would be really appreciated!





RE: French Drain
Another alternative would be to regrade the landscape, providing a landscape swale around the perimeter and discharging down the hill parrallel with the home. Alot of time when grading lots with drainage from back to front the landscape swale is provided, but over time and homeowners they slowly get filled in, then creating puddles. So it may nearly be that the landscape needs to be reworked to emulate the orginal intent of the lot. Not alot of fun though because I imagine your landscape is set and you probably don't want to dig it all up, but then again it is the best way to remove the standing water and assure yourself there wont be any additional flooding.
HTH
BD23
RE: French Drain
The french drain could work if it is installed at lowest area and you leave the rock/gravel exposed. However, it will be a continual maintenance nightmare and as silt/clay wash into the gravel, the percolation rate will be reduced. Eventually the gravel will need replacement, once it plugs up.
Another alternative is a series of small plastic catch basins suitable for pedestrian and lawn tractor traffic with 8" corrugated polyethylene plastic pipe such as ADS, NDS locatede at low points. Try to maintain 12" of properly compacted cover over the pipe and a minimum slope of 1% (less is you can accurately lay the pipe, but more is better until your outlet velocity is excessive and causes erosion.) End the pipe at a 4" concrete mitered end wall to a swale to daylight or a spreader swale. You could end the pipe at a bubbler (a catch basin that flows "backwards, but this will be a maintenance hassle.)
You could always high an engineer to properly design your system or waste $5,000 like my neighbor did. He had his buddy, a "grading contractor", improperly install a system that needs lots of maintenance and functions poorly.
Clifford H Laubstein
FL Registered PE 58662
RE: French Drain
The french drain could work if it is installed at lowest area and you leave the rock/gravel exposed. However, it will be a continual maintenance nightmare and as silt/clay wash into the gravel, the percolation rate will be reduced. Eventually the gravel will need replacement, once it plugs up.
Another alternative is a series of small plastic catch basins suitable for pedestrian and lawn tractor traffic with 8" corrugated polyethylene plastic pipe such as ADS, NDS locatede at low points. Try to maintain 12" of properly compacted cover over the pipe and a minimum slope of 1% (less is you can accurately lay the pipe, but more is better until your outlet velocity is excessive and causes erosion.) End the pipe at a 4" concrete mitered end wall to a swale to daylight or a spreader swale. You could end the pipe at a bubbler (a catch basin that flows "backwards, but this will be a maintenance hassle.)
You could always hire an engineer to properly design your system or waste $5,000 like my neighbor did. He had his buddy, a "grading contractor", improperly install a system that needs lots of maintenance and functions poorly.
Clifford H Laubstein
FL Registered PE 58662
RE: French Drain
We dig the trench at least 36 inches wide and 16 inches deep. The slope of the pipe is crucial to the success of your French drain. So the grade is very important. The trench should slope at least 1/8 to 1/4 inch-per-foot towards its outlet. Lay geotextile, a permeable non-degrading fabric leaving enough to overlap 12 to 18 inches at the top. Spread two inches of gravel or rock (3/4 or 1.5 inch) on the bottom. Locate and install two or three collection boxes as appropriate. Then lay two or three 6” perforated drainage pipe (function of runoff flow) wrapped with SOCKS in the bottom. If the pipe is perforated on one side install with the holes in the lower side. . Tie the collection boxes into only one of the pipes. Then fill with crushed stone to about 6 inches from the top. I put about 2 inches of pea stone next (small crushed stone). Over lap the geotextile fabric and back fill with coarse mason sand.
Additionally consider guttering the run off from the house to the drains.
RE: French Drain
RE: French Drain
Cheers
RE: French Drain
Its one of those things that theory cant support, but works well in real-life situations.