Another retaining wall ?

[ALBALD1]

My backyard is flat about 14 feet out & then goes up a bank thats rather steep for the riding mower. Its rideable, but a little intense. I'd like to build an interlocking block retaining wall about 3-4 ft high at the base to make it a little better & put a patio up to the wall. I've read how to put the drainage pipe in the back of the wall. However, I'm not sure how to drain the water running from the house side of the wall. I've got a slight slope away from the house all the way around to run water from the house. Its not a lot of water, but it needs to go somewhere when it rains heavy. My question is, does it just seep thru the wall & into the same drain or will it need ditched on the front side of the wall?

[twstanley]

If the first low spot where water can collect will be the base of the wall and you have a big enough area producing runoff, I would guess you could have enough water going there to cause problems...you mentioned a patio going up to the base of the wall right? You could always put some drainage grate around the edges of the patio to catch any moisture headed towards it from the house and drain it away ... someplace.

Where could you send the runoff that is headed towards the patio? You could always dig hole and put in a gravel fileld sump to dump it in. Like these:

http://www.ndspro.com/Flowell.asp

[SLOBuds]

Hopefully I am picturing this correctly in my mind.

I have a house, with a walkway next to it (gravel), a 4' retaining wall as yours, and then a sloped back yard.

You should have a french drain on the back side of your retaining wall and a second french drain between the house and that retaining wall. That will allow the water to drain away from the house, and it will keep the foundation of the retaining wall solid as well. This is all quite a bit of work. But in my mind I like to do these things ONCE rather than over and over again.

I learned quite a bit about french drains when I bought my country property 2 years ago. The previous owner let dirt coast down onto the wood siding, up about 6-10" from slab level. That is the worse thing that can happen to you. So I became familiar with how to construct french drains and now everything is squared away.

Water is our enemy! [img]/forums/images/icons/smile.gif[/img] (And also our friend, I guess!)

Let me know if you have any questions about how to put those things in.

Martin

[Pat]

ALBALD1, Be careful if yo go over 3 ft in height of retaining wall. Engineering considerations as well as liability and insurance considerations my raise their ugly heads. A GOOD French drain is a great piece of insurance and can't be overemphasized. Some interlocking retaining wall systems are designed to leak freely and not hold back water. These may be fine without a French drain but may require a gravel backfill and geotextile is a good piece of insurance to prevent the gravel from getting plugged up.

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]

[ALBALD1]

thnx for the info guys. I'm gonna have to study up on french drains. i've heard the term, but don't really know what it is.

[ALBALD1]

after reading a little about french drains, it seems too simple. just put gravel in a ditch then a perforated pipe wrapped in fabric & more gravel. No dirt on top, just gravel. Does this sound right?

[twstanley]

That's it, they work great. Make sure you have the recommended slope in the ditch so the water will move where you want it to, not just sit in the pipe and stagnate.

At the end of the pipe you can have an outlet at grade or dig a gravel filled sump for the water to go into to drain down into the soil....

[ALBALD1]

How do you determine the depth & pipesize?

[Pat]

Unless you have an enormous flow of water, you will get by fine with 4 inch black plastic perforated flexible drain line that comes in rolls at the big box stores. You can buy a "sock" (also in long rolls) made to fit over the drain pipe and prevent the perforations from being plugged with fines. This pipe is also available in unperforated if you need to lead the water away from the area of the French drain.

The BEST constructon detail is:L

1. put down geotextile
2. put down 3-4 inches or more of gravel
3. place your sock covered drain pile on the gravel
4. cover with more gravel
5. pull the "extra" geotextile up and over from both sides to cover the gravel
6. at this point I "pin" the cloth together with galvanized nails every foot or two.
7. cover with at least enough gravel to hide the cloth.

You don't have to do all of this to make a good working French drain but the above will help ensure that it CONTINUES to work well in the future by avoiding fines infiltrating the gravel bed and plugging it and or the drain pipe.

Use washed "SEPTIC" gravel as it has no fines to plug up the drain action. Ground up recycled tires are a good gravel substitute and are much much easier to shovel than gravel if you are doing this manually, sans FEL.

If you really want to be proactive, install a cleanout/flush port, a provision to flush the inside of the drain pipe with water from a hose.

I have installed several French drains and have NEVER had a failure or reduction in function. My most recent French drain installations are for my walkout basement. (See Oklahoma farmhouse thread in house building)

My walkout basement floor is from 1-4 feet below the ground water level most of the time and is protected by French drains which have been flowing continuously since installed over two years ago. Floor is quite dry.

[img]/forums/images/icons/smile.gif[/img] Pat [img]/forums/images/icons/smile.gif[/img]