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Should I tie existing porch slab to new foundation wall?


mossman's Avatar
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VA

08-12-17, 10:02 AM   #1 (permalink)  
Should I tie existing porch slab to new foundation wall?

I'm about to have the stem walls formed and poured for my attached garage addition, and the left side wall will be butted up against the existing porch slab, which was cut back a foot or so. The slab has no rebar embedded in it and is resting on top of two short stem walls. I don't believe there is much if any fill underneath. Since the side was cut back, the porch now has about a 2 foot cantilever. Would it be a good idea to attach the new foundation wall to the porch with a few pieces of rebar to give it support? Or should I simply backfill under the cantilevered area? Both? Alternatively, perhaps it would be better to make thr new wall a few inches thicker on that side so the porch slab has a couple inch lip to rest on. Although the guys that poured the footing ls screwed up so that there likely isn't enough width for a thicker wall. Code specifies a 2" minimum projection, which is already cutting it very close. That being said, drilling and inserting rebar (with epoxy) may he my only option. Leaving a 2 foot cantilever doesn't sit well with me.

 
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Pilot Dane's Avatar
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08-12-17, 12:32 PM   #2 (permalink)  
If I understand correctly I would fill underneath the cantilever. If it's not a huge volume I'd fill it with concrete. When pouring use a stick or shovel to shove the concrete up under the overhang and get rid of any voids. If the void is large then I'd backfill with clean crushed stone then cap with a layer of concrete that you can pack underneath the overhang to make sure it has good support.

 
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08-12-17, 05:13 PM   #3 (permalink)  
Here's a photo. So would tying the new wall into the slab be a bad idea? Say if the new foundation settled it would pull down on the slab and potentially crack it? The slab still needs to be cut back 5 or 6 inches, so the overhang will be 16" max (currently 21"). If it isn't obvious, the bottom of the photo is the new footing that was just poured.

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08-12-17, 06:12 PM   #4 (permalink)  
My fault...the slab is actually supported along the house as well by a 6" shelf (top of foundation wall), so maybe I don't need to do anything.

 
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