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Old 02-23-2012, 12:57 PM   #1
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Courtyard wall - subbase question

I'm going to build a 5' courtyard wall that will double as a retaining wall (no slope). I live in Phoenix, AZ and the previous owner had built a 2' retaining wall out of natural rock/boulders without any gravel backfill or fabric, so dirt continually washes through the wall. The wall separated two different levels of the yard, but there is no slope. So, I'm replacing this "rock wall" with a wall consisting of a concrete/rebar-reinforced base utilizing 8" CMUs with a stucco finish on the exposed sides.

My question is the subbase of the footer.....I'm trying to re-use as much of the onsite materials as possible, and there is a lot of 3/4" granite with smaller aggregate mixed in. I was thinking of having some 1/4 minus or sand delivered to mix in to make it more compactible. Will this 3/4" mix be suitable as a subbase or should I just go with an ABC mix?

Re-using the 3/4" granite will save $ by not paying to have the 3/4" granite hauled away and having to buy ABC, but I don't want to compromise the project. And I already plan on using the 3/4" granite for backfill/drainage, and will still have plenty.

Any other advice?

Thanks for your help!


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Old 02-26-2012, 11:44 AM   #2
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Ayuh,.... I can't feature why the 3/4" stone won't compact, All by itself....

Pound it with a plate-tamper, 'n get to buildin' yer walls....


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Old 02-27-2012, 09:02 AM   #3
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some resources

Hey there, I don't know how helpful this is but this site has a lot of data on retaining walls: could be a good resource.
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Old 02-27-2012, 12:39 PM   #4
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Since you are building a 5' high wall that also retain some soil, you will need a concrete footing or else you could end up with 5' wide sidewalk and hopefully no one will be under it. Depending on the height of the unbalance backfill retained, you have to make the concrete footing wider.

You should have a compacted base under the concrete footing. Clean 3/4" rock does not really compact in the long term (but adding some 1/4" minus and/or coarse sand can help) Any clean rock seems to work at first, but it can be pushed into the existing soil. Your existing soil may be acceptable if compacted (if slightly dampened) with a heavy plate on and pole or pipe and a lot of sweat or just rent a vibratory compactor.

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