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I've got an 8' retaining wall, runs about 120' across the back of my property (faces my house). It's railroad ties and has about run its life.

I'm looking to replace with some kind of stone/block wall. Had contractors out for bids on using engineered block.

But I'm also wondering about what's called "Boulder walls". Basically, just stacking (with skill) large 1000+lb boulders in place, after digging out the ties, then backfilling with gravel, plus using a french drain along the top to drain off excess.

Is this something that's not advisable in this area, or would it be ridiculously expensive vs using block, so no one does it?

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check your local code, but around here, anything taller than 3' requires a local engineer to help. They'll be the ones to tell you what techniques would be advisable. –  DA01 Jun 6 '11 at 18:39
    
How far is it from your house? What is not the other side of it? E.g. how inportant is the wall! –  Walker Jun 7 '11 at 8:08
    
It's behind the house, at the closest, about 8' from the exterior wall of the house. it's holding back the hill above me, keeping it from sliding into my pool (or my house), so pretty important <g> –  drventure Jun 9 '11 at 19:49
    
You wanna build a wall like that you will need a South African Wall builder. I built a wall like this around my property using large boulders/rocks that were just lying around. I actaully used 3 guys who did this for a living. Not the brightest bunch but they knew how to do it. It was HELL to build..(we laid a concrerte foundation and built ontop of that) but it looked like a castle (we sold the place) if only i had a picture somewhere... –  ppumkin Jul 7 '11 at 10:10
    
This is the part we built using rocks. I never made photos build google maps did :) goo.gl/93XjG –  ppumkin Jul 7 '11 at 10:17
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2 Answers 2

The engineering on such a wall may prove difficult. We recently built a 6' retaining wall and a couple of 5' retaining walls. The 6' wall was 32 MPA concrete spray using our pool as the footing, the 5' walls are steel reinforced, core-filled besser blocks with footings 600mm deep and 1000m wide. In both cases, using steel and concrete, the engineering was complex. We rendered both walls. We constructed our walls this way to minimise the foot print (the walls are 200mm thick).

Using something like boulders could prove tricky unless you have a 45 degree angle of repose - this would simplify things but also eat up a lot of your back yard.

My neighbour has just build a shorter retaining wall with besser blocks then added a rock finish afterwards - looks rather nice.

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That's probably the right way to do it, but you're right, that's a complex engineered wall, which means big $$$. Sigh. May be my only option though, unless another possibility pans out. –  drventure Aug 10 '11 at 20:41
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This sounds like an approach that might work but being so high it probably does need some professional help with the design and some experience in the construction. I suspect that you will need multiple layers of boulders, especially towards the base although it will depend on the shape of the boulders you want to go for.

One alternative you might to look at could be a Gabbion wall. This uses smaller rocks in a stainless steel cage to form cube shaped units which are then stacked. I've seen this sort of system very effectively used to support Walls of a similar size to the one you describe.

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Yeah, I know I'll definitely have to have some engineering done. In this area, it's just been difficult to find anyone that even does walls like this. Might end up being prohibitive just because of that. I hadn't thought about those Gabbion walls but I know exactly what you're talking about. Unfortunately, this will be going in behind my house facing the house, so I don't think that kind of wall would have a very high wife acceptance factor <g> –  drventure Jun 9 '11 at 19:48
    
The gabbion wall was nixed. Building codes don't allow that. I was a bit on the fence anyway with it, cause those tend to be a tad industrial looking... But thanks for the heads up on it! –  drventure Aug 10 '11 at 20:40
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