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CJIII 10-24-2012 08:01 PM

floating slab for a one car garage?
I am looking at pouring a floating slab for 12x20 one car garage. I live in Alabama and we dont have much of a frost line. I am wondering how hard is it to pour a floating slab? and do you need to use achor bolts?

GBrackins 10-25-2012 09:18 AM

depends on your level of experience and what result you are looking for.

you need to use anchor bolts to attach sill plates to the foundation. being in Bama I take it you are placing a combination foundation footing and slab (monolithic)?

joecaption 10-25-2012 09:29 AM

Google stem wall foundation.
It's a far better way to do it, it will get the walls of the garage up away from the grade.
Just look at some of the hundreds of old post on people now having to deal with water coming in under the walls, rotted siding, rotted bottom plates.
I would strongly suggest you hire the foundation part out and have a real concrete finisher do the slab.

CJIII 10-25-2012 09:47 AM

Yes a monolithic slab.

GBrackins 10-25-2012 10:03 AM

then you would need anchor bolts for the attachment of the sill plates to the foundation. sill plates are used to attach the walls to the foundation. I agree with Joe about having the top of foundation above the slab.

CJIII 10-25-2012 08:36 PM

I really cant afford to hire a concrete finisher.

Canarywood1 10-25-2012 08:42 PM


Originally Posted by CJIII (Post 1037388)
I am looking at pouring a floating slab for 12x20 one car garage. I live in Alabama and we dont have much of a frost line. I am wondering how hard is it to pour a floating slab? and do you need to use achor bolts?

All you need in your area is a floating slab,with a 4 inch wide x6 inch high curb around 3 sides of the slab,and stop the curb where your overhead door go's on the 4th side.

CJIII 10-25-2012 09:52 PM

Thats what I thought.

GBrackins 10-25-2012 09:55 PM

I'm sure you have a minimum footing requirement, probably 8" x 16"

GBrackins 10-25-2012 09:58 PM

a typically slab received 6 mil poly vapor barrier under the slab with seams lapped at least 6-inches on top of a compacted level base. you'll want to use welded wire fabric mesh at a minimum to reinforce the slab, mesh typically goes in the bottom half of the slab.

CJIII 10-25-2012 10:03 PM

For buildings under 400 sq ft. We dont have to have a foundation.

GBrackins 10-25-2012 10:07 PM

oh, ok

Daniel Holzman 10-26-2012 09:14 AM

Pouring a monolithic slab may sound easy, but it is hard work, and difficult to get right. At 240 square feet, and 4 inches thick, you are looking at 80 cubic feet of concrete, which is 12,000 lbs. That is a lot to mix using a mixer, so presumably you are planning to buy ready mix, three cubic yards.

The truck is going to show up and want to begin dumping concrete immediately. If the concrete sits in their truck too long, it begins to harden, and this is a big problem for the transit mix company, so ready or not they are going to dump the concrete into your forms. So you need to be ready to spread the concrete and level it immediately, which will take a couple of experienced helpers.

Certainly this can be done, but the results will certainly be lower quality than a professional company. That may be OK with you, a few cracks in the floor may be OK, a floor that is not quite level may be OK, a floor with a poor finish may be OK. Finishing is probably the part that requires the most experience and skill, but only you can determine how much a quality finish is worth to you.

Mort 10-26-2012 10:24 AM

To add some to Daniel's suggestion, that three yards will just cover the slab, not the curb or the footing. I'd suggest at least 4 yards, maybe more, depending on how deep your footings are. This will also give you a little breathing room in case your calculations are off, or your grade is off, or will compensate for yield problems at the concrete company, etc.

I see that Alabama is a rear-discharge concrete mixer market, so you'll have to know a bit about how they work. Luckily, there's a thread about that:


The most important part would be the hand signals, for the beginner anyway.

CJIII 10-26-2012 08:28 PM

Are their any good books on pour a concrete slab?

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