Suspended Slab Infill

[psychedomination]

Hi there,

I'm working on a project, where there is an existing opening that an Architect is trying to close up to create a building extension.

See the below detail from the Architect. I need to design the infill.

It seems like the simplest approach would be to design the slab to span the long direction (say 7'8") and then provide minimum reinforcement in the short direction and provide nominal dowels to tie the new slab to the existing beam to reduce the risk of deflection differences. With this approach, I won't need to rely on the existing LB3 to take any of the additional load (even though it would likely be small anyway).

See sketch below :

I didn't mean to put a question mark after "currently an open void". It is currently open and will be closed in with the infill.

Initially my main concerns were regarding the joint between the new slab and existing beam e.g. water leaking and differences in deflection. However, there will be a ditra mat on top of the slab with tile/mastic etc, so I believe it's unlikely that leaking would be an issue?

Asking to see if there is a better or typical detail for situations like this.

 

[JAE]

Why concrete?

If it is closed off and not seen you could simply frame it with lumber and plywood and seal it off.

Also - for a long, rectangular slab, not sure just "choosing" to design it the long way works. Force follows stiffness and the slab will not really flex the long way if you dowel it into existing supports each side.