Installing a French Drain Behind a Retaining Wall
Вставка
- Опубліковано 21 вер 2018
- Check out this video for some simple instructions on installing a French Drain behind an 18” to 24” tall retaining wall before it is backfilled with dirt. You can also check out our website for more how to PDFs as well as to see what materials we might have to help you with your next project. www.btymaterials.com
- Навчання та стиль
Yes very helpful! Thank you
Awesome video!!
I wanted to like it..... but it is on 420 likes right now, and I don't want to mess that up, lol
I like it, but I would wrap the pipe in fabric and put nothing but rock over that.
Great info.🇺🇸🇺🇸🇺🇸🇺🇸💯
Great video! Is there a way of installing adequate drainage to an existing retaining wall retrospectively without going to the effort of removing all the backfill?
As a work around, you might be able to install a French Drain along the top of the wall (depending on water flow) to help water move away from the wall, which would help some of the water not seep into the soil, and potentially alleviate pressure against the wall. It would be a similar process to installing a drain behind the wall. We’ve got a PDF that you could download for some additional information for this method on our website. You can check it out by going to our site (btymaterials.com) and finding the Knowledge Base page. Issue #2 is about working with French Drains. I hope that might help!
Is the drainage pipe connected to the weep holes? If not, is it placed above, or below, the weep holes?
The base of the drainage pipe rests at the same level as the base of the weep hole pipes, with the drain pipe right up against the wall and next to the weep holes. As water fills the drain pipe, the water escapes to the weep holes as the water finds the paths of least resistance. The drain pipe has slits on all sides so that water can enter and exit the drain pipe. I hope that helps!
My wall is 4ft tall, 70ft long, in front of a slope. It is leaning forward. It has been there about 25 years. It is made of stacked blocks with pins. It has a french drain behind it and in front of 1/4 of it. I believe that their is a Y at the end of the wall where both drains converge and go on down to a ditch. When it rains heavy, water comes through the brick and it floods the entire 70ft of the front of the wall up to about 8 inches deep, 7 ft wide until the lower french drain finally catches up, which takes about 30 minutes. The drains are 4" corrugated. I am considering restacking the wall, replacing the drain behind the wall with 6" and run that drain independently down each side of the wall out to end of property on both sides. Maybe put a few basins behind the wall as well. What are your thoughts? How deep should I bury the 6" french drain behind the wall? Thank you for reading all of this! Wish I could send a picture. Jim
reply sent on FaceBook from message there. Thanks!
@@btymaterials thank you for the excellent information!
Would this be fine to do under a shed base. I’m building a retaining wall because my yard has a slope and I would need one underneath one side of the shed.
vincent yacobozzi you can definitely run a French drain under your shed but in the area you won’t be able to get the compaction for the soil that you would otherwise desire. Depending on the construction of your shed, especially if you’re doing a concrete slab, you might look at doing some small bell shaped piers to help ensure your shed doesn’t start to settle unevenly.
What about a landscape timber retaining wall where it wasn’t built with drainage. I do not think I can dig all the way down, but should be able to get down a couple feet. Any value in installing the drain line and gravel down as far as I can go, even if I can’t get all the way down?
Brett Cohrs a Drain line would probably help the water to go out to a specific location instead of draining out between the timbers. You would definitely at the least what to line inside of wall with fabric and back up the other side of the dirt so that you have a void area that you back fill with rock and have wrapped in fabric much like i did in the video, with or without the drain. Again, the timbers will allow drainage but might cause issues on the front side of the wall if you don’t use a drain. You want to make sure you at least have the wrapped rock in fabric and not just back fill with dirt. If you just use dirt, over time the dirt will push against your wall and cause it to fail. Let me know if any of that doesn’t make sense or if you have any other questions!
By The Yard Materials Thanks. So you’re saying that it would do some help to put the French drain in their as far down as possible (using the appropriate technique with gravel, landscape cloth, etc)?
Brett Cohrs yes sir. If it was mine, that is definitely what I would do!
My question is ... does the geo filter material eventually clog up and render the drain useless . Good vid by the way 👍
Gus M the fabric I use in the video is actually a 4.2 oz filter fabric that is approved for state use as a filter material. It is a very good quality material. I can not imagine it ever clogging up but the longest I can personally say I have had it in place is about 5 years. Additionally, with the permeability of the soil and with waters natural ability to seep through soil and this fabric, I can’t ever imagine it clogging up.
Gus M I might add you would want to make sure the soil is not just a thick clay material with a high plasticity. You would want to make sure it is a sandy loam or has some sand base to the soil. This allows water to pass through the material. If you did use a heavier clay material you might run into to drainage issues depending on the depth, but more due to the soil than the filter fabric or drain. The more clay the higher the plasticity which means the longer water is taking to penetrating the soil.
Water rises from the bottom up but you put your perforated pipe with the slits at the top. I think they’re supposed to be facing the bottom so that as water rises it enters the pipe. If the slits are on top, there will be a build up of water until it reaches the top of the pipe.
The pipe has slits all around the pipe, not just on one side.
I am building a stacked block retaining wall and I'm wondering if I should run a piece of geofabric for drainage from the ground all the way to the top of the wall with drainage gravel between the wall and the fabric and backfill dirt behind the fabric. I believe my design is correct but just want to confirm with someone who has more experience.
That is correct. You want the geo fabric to separate the gravel from the soil, from the bottom to the top. I’d say you could even go as far as wrapping the rock like a burrito in between the wall and the existing soil just to make sure your drain line stays free off sediment. At the least maybe 1’ from the bottom on the wall side and definitely covering any exposed gravel on the very top. Make sense?
@@btymaterials Makes perfect sense. Thank you for the quick response and I appreciate your advice!
What about all that dust / very small particles in the rock, won't that clog the Pipe ? I think it would be feasible to rinse / wash the rock off before filling on top of the Drain Pipe !?
Kevin,
The 1" Limestone is a washed product and meets the specs for ASTM #57 stone to be used in concrete production. It does have some dust but is a relatively clean material (at least here at our yard). Additionally with a slatted perforated pipe, I did not have much concern with the pipe getting clogged. If it is still a consideration for you however, you can simply wrap the perforated pipe with fabric prior to installing.
Kevin Stailey you can add a cleanout if youre worried
Most of the dust /particles will flow around outside pipe to bottom. I wouldn’t bother with a cloth around pipe if geo fabric is done correctly. Amazing how many argue to just wrap pipe , gravel then dirt with no fabric separating gravel/dirt. Im certainly no expert and it’s obvious that career landscape / drainage guys don’t even agree on how to be done.
Im doing my first underground drainage and retaining wall..I absorb everything I learned(after watching everything 10 times while I’m working) and do what makes sense to my application. Ur explanation was concise, informative, and no unfamiliar jargon. Thanks!
I’m getting ready to do a 2ft tall, 90ft long wall. My plan was to backfill completely with gravel and then use a lil soil on top for the last 3in or so. Will that work?
Yes, as long as you wrap the rock in filter fabric to keep the dirt out, it should be fine... typically I believe 3-4" is needed for grass.
@@btymaterialsthx. My plan is to use a 4in corrugated perforated pipe that already has the filter built in. Does that sound ok in your experience?
you can use that to keep particles out of the drain, but if you put soil on top of the rock, you will want to use a filter fabric at location as well. Otherwise, the soli will filter down through the rock and eventually cause drainage issues as the water will not be able to drain as freely. It will also cause your soil to settle unevenly as it drains down into the rock. I hope that make sense. It’s best to wrap the rock up in filter fabric like a burrito to keep the soil out
What to do with ends of pipe? I have 90’ brick back-wall with wooden fences on both sides. If I pipe ends are open, wont water log and damage wooden sides?
Without being able to see the project, I would advise that the ends of the pipes either need to be able to drain out and run off to a lower area, or you would need to have a sufficient number of weep holes across the front of the wall so that the water is able to drain out. You are correct that you do not want water to pool near the fence. The function of the French drain is to allow water to drain to lower areas either from the ends of the main pipe or from weep holes, etc. In the video that we made above, the ends to the pipe are just wrapped in filter fabric and do not drain out to a lower area. Instead, we have weep holes along the front of the wall where the water is able to escape that is collected in the larger drain pipe. These weep holes are placed about every 8 feet which works well with our set up. I hope that helps!
Where do you recommend getting the drainage pipe?
Brett Johnston Lowe’s or Home Depot or similar big box store will have the 4” perforated pipe in 100’ rolls.
If the tubing is below the surface, at the base of the wall, where does the water exit?
The perforated pipe rests at the base of the wall. The wall should have weep holes installed so that as the pipe fills up, it drains out the weep holes through the front of the wall in this application. If the retaining wall is open on one end (or both) and you do not have weep holes, you could try to pitch the pipe toward the open end, and with the correct amount of fall you could allow the water to run out the end as a possible solution. I hope that helps.
Common mistake is the drain pipe is installed wrong, upside down. Holes should be at the bottom, or below 3:00 and 9:00.
common but extremely critical
Was thinking the same thing
This particular drain pipe has perforated slots all around the pipe.
I call bull creak....i never see any water drain from the several wall I see...