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CJIII 12-18-2012 05:04 PM

Would 3 or 4 yards of concrete cover a 12x20 garage?
I am wondering would 3 or 4 yards of concrete cover a 12x20 garage foundation with a 12''x12'' footing?

Bondo 12-18-2012 05:07 PM

Ayuh,... Do the math,... a yard of concrete is 27 cu. ft....

12'x 20'x how many inches,..??

Daniel Holzman 12-18-2012 05:13 PM

For the footing, each linear foot requires 1 cubic foot of concrete. You have 60 linear feet of footer, hence 60 cubic feet required there. The slab is 240 square feet, so for a 4 inch thick slab you would need an additional 80 cubic feet of concrete, for a total of 140 cubic feet, which is a little over 5 cubic yards. Due to spillage and waste, best to order 6 yards of concrete. Unless of course your slab is not 4 inches thick, in which case you need to modify the computations.

CJIII 12-18-2012 05:18 PM

Yes the slab is 4'' thick.

joecaption 12-18-2012 06:53 PM

I personaly would never suggest anyone DIY there own slab. Seems ike a simple job, but it's not.
It's a one shot deal, once that truck pulls in there is not do over or just make it work.
Even the lay out, footings, height of the slab, the slope toward the front can be tricky.
Have you taken into consideration that the bottom row of siding needs to be at least 6" off of grade?
Have you concidered using stem wall constrution?

woodworkbykirk 12-18-2012 07:30 PM

4" slab on a 12 x20 works out to .3333x12x20 / 27 +10%= 3.256 yrds round up to 3.5 yrds if you can get 1/2 yrd ordered otherwise get 4

concretemasonry 12-18-2012 09:20 PM

Better to order too much since concrete is not that costly once you reach the minimum delivery amount. Nothing is worse than coming up short if you did not have base under the slab graded as accurately as you want you pencil will be in figuring costs in advance.

Plan ahead and make sure you have something formed in advance that you ultimately need - sidewalk, apron, etc. to use up any excess. Much better than just dumping it in the wrong place.

the biggest mistake with concrete pours is to not have enough (poor concrete job with cold joints) or enough help to place it quckly if the weather turns. - Also have protection for rain or snow.


CJIII 12-18-2012 09:27 PM

I understand that pour concrete is not a DIY job, thats why I thought about doing a wooden floor.

CJIII 12-18-2012 09:49 PM

I figure it was 4 yards.

BigJim 12-18-2012 10:00 PM


Originally Posted by CJIII (Post 1075722)
I figure it was 4 yards.

CJ, It would be a little over 3.5 yds for just the slab, but you said you were pouring 12X12 footings so you will need at least 6 yds like Daniel said.

ddawg16 12-18-2012 10:20 PM

Are you pouring that with a totally flat floor? No stem wall?

For reference, my floor is took 20 yards of concrete.....oh, the footing is 18"w x 24" deep and has an 8"h x 6"w stem wall all the way around. I love that gets my walls at least 8" above the ground and on the inside....all my cabinets sit on the lip of the stem wall anchord to studs....nothing touches the floor....makes it easy to wash out the floor.

If you want to see on the garage build link in my signature.

CJIII 12-18-2012 11:07 PM

Ok thanks!

CJIII 12-18-2012 11:10 PM

The reason I wont concrete is that I will be using the garage as a woodworking shop!

joecaption 12-18-2012 11:18 PM

Going to be tight in that small an area trying to use it for a wood working shop.
Have you done a simple lay out on some graft paper to see how it's going to look.
Just been there far to many times. Built the garage, moved eveything in, find out it's to small and have to go back to working outside.

CJIII 12-18-2012 11:29 PM

I know its small but my current shop is 10x12 shed.

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