Old 08-27-2001, 11:36 PM
BRL BRL is offline
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Location: Somerset, NJ
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Retaining Wall Drainage Questions

OK I've reviewed our great threads here and have some questions. I'm doing 2 different walls at 2 locations and in both cases I'm able to cut the existing ground exactly where I want the back of the walls to be. The are both going to be using natural stone, or what Steveair has described as PA Fieldstone. I'm in NJ also so my suppliers call it that too. Both will be no higher than 12"-14" above grade at their highest points. Being this low, is it absolutely necessary to back fill with gravel and provide the drain pipe if I'm able to build these against undisturbed & solid existing ground?

The reason I'm asking is the one wall is going in a shaded yard with a beautiful lawn of moss. Yes moss. And if at all possible I'd like to not disturb it. The other one is at my house so if I can save a buck it would be cool. The one at my house is going where I had widened my driveway. My front lawn has a slight slope toward the street in front, so the wall would be running parallel to the natural drainage direction. So if I don't have to tear up any more of the turf & spend time & money with that, I'd be happy. I had cut the existing soil to widen the driveway 2 summers ago and there has been no erosion of that unretained wall of existing soil in that time. So I'm figuring it shouldn't be a problem to install the wall there with out the gravel and drain pipe. Should I reconsider for these 2 cases? Thanks for any comments & suggestions.
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Old 08-27-2001, 11:51 PM
paul paul is offline
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Set the base on gravel and add a couple of inches behind it as you go up. Pipe you don't need it for a wall that high.
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Old 08-28-2001, 07:57 AM
steveair steveair is offline
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I have a wall, 18" high, that I built using fieldstone at my parents house a few years ago. It was about 30 feet long, and was built into 'virgin', settled ground.

What a mess that wall is now!

A lot of water, for some reason, runs down this 'slight hill' behind it, and through it. I set it on a compacted QP base, and backfilled using 3/4 crushed.

I figure it is going to fall over in another 2-3 years.

Just a warning. The problems I think the wall had, were for 1 it was not built thick enough. I was trying to economize as it was for my parents, and well, should of built a little more bulk behind it. Second, I should of put a pipe behind it and a lot more stone.
To be honest, I just didn't expect that much water being present in that area. I also built a patio a few years ago, and now, the water comes through the wall, under a deck, and across my patio. I even put in a french drain and a 6" catch basin knowing the water problem was there, but it still flows like there was a river running there whenever we get any kind of rain. Its a very strange site, and for the life of me, I can't figure out where all the water comes from.

Just a 'real world' experience I'd thought I share.


Last edited by steveair; 08-28-2001 at 08:05 AM.
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Old 08-28-2001, 01:54 PM
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Stonehenge Stonehenge is offline
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I'm with Paul.
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Old 08-30-2001, 12:34 AM
BRL BRL is offline
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Thanks guys. I'll go with Paul's suggestion. Question though.
"add a couple of inches behind it as you go up." I'm guessing a couple of inches in height, to leave room for existing soil on top. How deep (going perpendicular from the wall) do I want to go with the gravel? Thanks.
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Old 08-30-2001, 08:07 PM
CHC CHC is offline
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We built one like this about 5 years ago. We used fabric right behind the wall to keep the mud out, and 6" of gravel behind the wall. Its still standing straight, and staying clean. Enjoy.
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