Foundations and Footings

[medeek]

I'm trying to determine which is the preferred method of blocking out a stemwall foundation for garage doors where a slab will be poured in the garage. I've seen it done both ways. Option 1 does not typically block all of the stemwall out and seems to be more common in locations where the frostline is deeper (24" or deeper). Option 2 completely blocks out the stemwall at the garage door and then a thicken edge is poured where the slab meets the footing at the garage door. From a structural point of view which is the better method and also from a constructio point of view what are the pros and cons?

Option 1:

Option 2:

[Jim Katen]

I've built them both ways. Back east, because of the deeper frost depth (as you say) we ran the stemwall all the way around, making it easier to compact the gravel fill.

Out here, everyone seems to omit the stemwall at the door opening and allow the slab to be thicker there. Since our frost depth is only 12" to 18" (depending on county) there's really no need for a stemwall. That's how I built my own personal garage.

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[medeek]

I should point out I've also seen a sort of a combination of the two options where the blockout does not extend to the footing but a thickened edge is employed at the slab/door interface and the thickened edge is typically 2x the slab thickness, or called out as a minimum dimension of 8".

Option 3:

[Jim Katen]

Other than providing some strength at a vulnerable point, I see little advantage in that method.

[kurt]

I cannot recall ever seeing a stem wall under a garage door apron, and we get frost >50" occasionally.

Nice detail, never seen it. Ever.