Connection between strip footing and slab on ground 1

[jefftang91]

Just wonder what kind of connection should I use between strip footing and slab on ground?



the red circle is the location I want to know.

thanks

 

[msquared48]

Drop the footing down and run the slab over the footing.

Mike McCann
MMC Engineering

 

[hokie66]

What are your other slab on ground joints like? Why not make them all the same?

 

[dik]

As Mike noted... but, I prefer to have a 6" granular 'buffer' between the slab and the footing... else, the footing edge can 'telegraph' through the slab.

Dik

 

[jefftang91]

To Mike, if I drop the footing down and run the slab over the footing, then that is no needed for the connection right?

To hokkie66, they are same, but I only show 1 side of it.

To Dik, can you talk deeply about 6" granular 'buffer',or maybe a picture of it to make me more understand.


thanks !

 

[hokie66]

My point was...if the footing is at slab level, it forms part of the slab on ground. I assume that the slab on ground has joints. If these joints are dowelled, use the same dowelled arrangement for the footing/slab joint. If not dowelled but just sawcut, I would provide a ledge on the footing for the slab to sit on. Or, as the other gents suggested, drop the footing, run your granular subbbase over the footing, and cast your slab on that. Depends totally on the usage of the building as to which solution I would use.

 

[aeoliantexan]

Practicing in the midwest, on non-expansive soils, we would run the slab over the footing and place a 1/2-inch control joint between the slab and the wall. The slab will cantilever and tolerate some footing settlement. if settlement is too large, the slab will crack anyway.
If the slab meets the footing as you have shown, a small amount of footing settlement causes an offset that will affect the floor covering. If you dowel them together, footing settlement will crack the slab or rotate the footing.
Another benefit of placing the footing below the slab is that a perimeter drain laid on top of the footing will have its flowlne below the top of slab level, reducing the chanace that water will come in. Building on clays, any time the exterior grade is higher than the floor level, there is a chance of water entering, and a perimeter drain is needed.

 

[msquared48]

I agree with dik here about the 6" granular fill too under the slab an over the footing. I commonly do that too.

And Jeftang91, yes, then no connection would be involved.

Mike McCann
MMC Engineering

 

[hokie66]

It is really impossible to generalize without knowing the usage of the building and the ground conditions. With post-tensioned slab on ground construction, it is common to cast and stress the slab first, then excavate and build the footing with its top at the same level as the slab.