I'm pouring a 20'x30'x 6" thick floor and plan to reinforce it with 3/8' rebar. What's the best rebar spacing?

Answer 1

When they poured the foundation for our house, they used 3/8 rebar on 12 inch centers.

Of equal importance is the strength of the concrete and the amount of water in the mix. People tend to make the concrete too soupy. Try for a 2 to 4" slump. It makes placing the concrete a little harder but you get fewer cracks when the concrete cures. It will also be stronger.

Also if you want a dry floor, you need to consider putting a plastic sheet under the the concrete with about 4 inches of dry sand on top. The dry sand will absorb the water that comes out of the mix as it cures and the plastic will keep ground moisture from migrating through the slab later.

The suggestion of an 8" slump is really not the best. 6" maybe but when you ask for 8", you may end up with soup and it is hard to remove water. Better to start dryer and add if necessary.

Answer 2

Both 1 and 2 offer excellent suggestions. I especially want to add the the suggestion about having the rebar above the ground/base/pour level; but that can be done by bending the rebar at a 90.

Since you don't state the purpose of the building; or your location as it equates to frost lines, etc. AND since you're pouring to 6 inches, my personal opinion is that 12 inches is a bit of overkill; but the cost difference would be minimal in going 18, or even 24.

Most single story construction here is 24; unless it's commercial.

Just my 2 cents.

Steven Wolf

Certainly an over dilluted fill will be an issue.

Answer 3

One foot apart. Place a few crossing the rows, too.

This is a good time to throw in old fencing. Have garden rake handy to lift up rebar when cement is being poured so it does not remain on the bottom. I had seen one guy found numerous short tree-branch Ys & stuck into prepared area, placed rebar on the Y fork so the rebar would remain more centered when pouring the cement.

Answer 4

2 foot center, make a grid with it. Tie wire it all together you dont have to tie wire every one just enough so it all comes up at once while you are pouring.Lift it as you pour or put broken chunks of brick under it.Dont pour it at a 2 or 4 more like a 6 or 8.Youll kill yourself and all your help and probably lose it. Pour at a 6 or 8 all the time never had a problem. Tell the ready-mix plant what slump you want.