Concrete Curb Foundation Alteration

[TRAK.Structural]

I've been called in to assist with a standalone residential garage project. The client/owner neglected to have a foundation inspection and now needs an Engineer to get the permits closed out. The foundation and superstructure is mostly complete, see pictures below. There are a few items that I think need addressing:

1. I don't like footings without rebar, even for residential work. Owner says there are (2) continuous bars but without being able to verify that statement I'm inclined to assume there are no bars and hence I want to add some.
2. These bldgs are super light and the amount of weight from the curb alone isn't enough to hold this thing down so I have to address this as well.

I've come up with (2) details to handle the items above. The first option is essentially just adding more mass of concrete to overcome the uplift force. The second option is similar however it also dowels into the existing slab on grade to lessen the amount of additional concrete that is needed. I think both details are do-able, but my gut says that either one is a lot of work. Anyone have any other ideas? I'm open to considering suggesting partial disassembly of the superstructure if there is a significant advantage as it relates to what would have to be done to the foundation.

 

[a_urbs]

How badly is this thing uplifting?

Could you locally drill and epoxy some dowels at the columns that need them most? I feel like that addresses the root of the problem the most directly. This depends on the height of the curb, SOG thickness, budget, etc though.

 

[jhnblgr]

What is the footing?
Is there a frost wall?
How did you figure the uplift forces?
Pour concrete on top of the steel sill plate

 

[TRAK.Structural]

a-urbs: Maybe, but that doesn't solve the issue of not knowing if there are any continuous bars in the curb. The curb would have to span far enough (unreinforced) to pick up enough slab to effectively overcome the net uplift. I can run the numbers on an unreinforced conc beam in this manner, and maybe it works, but I still don't like it.

jhnblgr: The curb in the sketch/pictures was poured on top of an existing concrete slab (likely 4 inches thick). Then the bldg was built on top of that. Concrete on top of the sill plate may work to provide enough weight. I'd be a little concerned that it would just crack and break apart over time and eventually be non-existent. Maybe if I added the dowels and a continuous bar as shown in the sketch below it would stay in place.

 

[a_urbs]

If the continuous bars are critical, call in a GPR or rebar scanning company to confirm that. If dowels connect the curb to SOG, you could count on some of that for uplift. If there are no dowels, you should probably check the sliding/shear interface as well, although I doubt it's controlling.

 

[shacked]

, I know it is only a light gauge metal garage, but no footing? Sometimes, in situations like this where the contractor obviously choose to do his own thing, they have to learn a lesson. I'd make em excavate on the exterior under the edge of the slab and pour a footing.