New slab for garage floor.

Old 05-23-06, 08:23 AM
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New slab for garage floor.

I'm planning to construct a detached garage (approx 30' x 24'), and will hire a contractor for excavating & pouring the concrete slab.

My problem is a rock shelf that is approximately 12-14 inches under the ground where I would like to build. My lot slopes in the area that I would like to build the garage, and I can go back further (from the house) to get more depth above the rock. I presume that the rock may cause drainage issues (?) - how much depth above the ledge do I need, and any suggestions for coping with this would be greatly appreciated.

I would really like to have the garage closer to my house, but I'm guessing that dealing with rock for construction would be more costly than I would like to invest at this point (plus I don't really want to blast close to the house).

I would like to have some solid ideas before meeting w/contractors for bids - thanks for your input.

Old 05-24-06, 12:56 AM
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This is really a question for an engineer, however the rock may actually be a benefit. Consider having it looked at by an experienced engineer, if for no other reason than to help you feel more confident when talking with potential contractors.
Old 07-13-06, 09:11 AM
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I can relate as I am having a garage built right now. The concrete was actually just poured yesterday.

I had lots of rock just under where I wanted my slab. I didn't know about it until after the concrete guys get their bobcat out there and discovered it. I am having a contractor do the entire garage with the exception of wiring, so a fee was agreed upon up front.

While the concrete guys were out there, I asked what it would cost to have him do my 24x22 slab if he were dealing straight up with a customer, and he told me about 3k dollars. He said if you know about the rocks and stuff like that up front, it's actually going to be more expensive... the lesson I learned from that is to agree and sign a contract up front. The extra two days it took to remove the rocks cost me nothing because of that.

Jackhammers and bobcats were used, and the rocks were removed.

Here are a few pics of what I was dealing with:

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