Connecting footer rebar with slab rebar

[Stitcher]

Hi.I have a question about how rebar is supposed to connect in a monolithic slab.I want to put down a 16" grid of #4 rebar in the slab and connect it to a 18"wide x 24" deep footer.Is there a diagram of this available somewhere to see the connections?Specifically the part of bending the rebar to meet up with the 4 rebar runs that will be in the footer. I live outside Fairbanks Alaska,and there is no code here,however,I want to build a strong foundation.I'm just a little confused with what this network of rebar should look like at that part of the slab.Thanks

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[DD_BobK]

Just put a 90deg bend the slab rebar with a ~18" tail on it and run it down into the footer. (make sure you have at least 4" of concrete between the bottom of the footer and ends of these down facing rebar)

I'd run a horizontal rebar in the footing at the 90 deg bend. And another horizontal piece at the ends of the 90 deg bends.

I'd probably do double 90's (out of plane) so the vertical tails also had some splice length with the lower horizontal rebar.

But all this aside.....Fairbanks has a pretty deep frost depth. A footing that is only 24" deep (unless heated / insulated) or on a well drained base is going to be at risk for frost heave.

Better check out cold environs foundation design before you waste a lot of time & money.

cheers Bob

[Randy]

Would a 24" footer be OK, due to the permafrost in AK? Once you get past the top surface than thaws and refreezes and you hit permafrost it's like buiding on bedrock is it not? Just guessing here.

Thank You, Randy

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[DanG]

You use the term slab. How thick is this slab? A grid of #4 bar requires a minimum of a 5" slab, 6" preferred. A slab is usually NOT fastened or pinned to a footing, in fact they usually have an expansion joint to allow slight separate movement.

If they do need to be tied, simple right angle bars would be the norm. 24" depth of footing won't work in over half of the continental US, I cannot envision it working in Alaska at all.

[PeterD]

Sure it will... They are called an "Alaskan Floating Slab". In fact, you don't even need 24", usually 18 is sufficient. The inside edge must be tapered however.

There are many good writeups on floating slab construction on the web.

[Tekkie®]

Stitcher posted for all of us...

What are you putting on this slab? #4 MAY be overkill. Don't usually tie a slab into a footer but you have to determine if it is necessary. Need a deeper footer than what you want and don't depend on the slab to hold or stabilize it. What are you putting on the slab? Do you need drainage around the footer?