Cavity Gap between new and old slab

[Galgt4]

Two questions, 

 

building single storey extension. Original inner slab is on block & beam and new outer is mesh slab (footings piled)

 

1. We have two engineering solid brick pillars to build for steel to sit on top. Took out both skins to build pillars and there is a cavity about 2ft deep. See image. Can we just shutter and concrete this void then lay dpm and build pillars on top? 
 

2. What do we do with the rest of the cavity between original slab and new slab when knock through is complete to join both floors?

[Russell griffiths]

I would say if it a footing to take a pier to take that steel which is holding the entire back of the house up, then the foundation should have a proper design by a structural designer, then the foundation same as the pier. 
 

this is not an area to be guessing or scrimping. 
 

@Gus Potter

[Galgt4]

5 minutes ago, Russell griffiths said:

I would say if it a footing to take a pier to take that steel which is holding the entire back of the house up, then the foundation should have a proper design by a structural designer, then the foundation same as the pier. 
 

this is not an area to be guessing or scrimping. 
 

@Gus Potter

Hi mate, 

BC said he’s happy for the pillars to be built up off the block from floor/top of slab level and only seemed bothered about insulating that section. This is why I’m questioning it. SE engineer just says make sure foundations ok with building control??  It’s built up with block from foundation to dpc then engineering brick. See image.  

[saveasteading]

It's not for us to say. It is a project specific thing, so your SE should advise on the structure, not the BCO.

The BC can advise on insulation and damp, not that they should be designing for you.

 

But as an overview, and as @Russell griffiths  .. that is a big beam with a big load and the footing is absolutely NOT designed to support it.