Pouring a slab over existing foundations

[i_am_fubar]

I'm on the final stage of excitations for a new workshop slab (6x2.8m).

100mm meshed pad with 350x350 beam with rebar around the perimeter. Single pour.

I have now found an old foundation in one corner and am concerned it will lead to uneven settlement (see pic) as it seems totally rock solid.

Am I ok to lay over it? And if so, shall I add a layer of compacted sand (I have about an inch I can add before it impacts the 350 depth) or go straight on top.

I'm adding a dpm tanking the whole slab and am leaning towards a sand layer to protect the dpm and allow for settlement movement.

Ta
Fubar.

 

[Wayners]

Clean it off.
You can add rebar with bolt resin to bind old concrete to new

 

[i_am_fubar]

Thanks wayners, but my worry is OVER constraining this. It's a detached structure that I imagine will settle independently to these legacy foundations (been no building on it for over 15 years and they're only just in the corner)

 

[Wayners]

I understand you're worry but you can't do much above it.
All buildings move a bit and have settlement. Concrete floor slab sinks a bit Vs foundations and new buildings have deep concrete foundations tied in with original older properties with next to no foundations. Just how it is.
Just get on and build it.

 

[JohnD]

excitations

Excavations?

 

[i_am_fubar]

Na, this is all pretty exciting. Never done a full building from scratch before

Wayners, I did wonder if I'm over thinking it. I'll add a bit of sand to protect the dpm and leave it at that. No need to join them together.