Extension Footings

[Bahco]

Furthur to my previous thread I have been told by BCOs that they require raft footings with Z steels approx 1 metre deep.
Does anyone know how much these Z steels are likely to be and how much ballast I will need for 3 trenches for ex measuring 18 foot by 10.
Also what do these steel thingys entail in putting them in.
He has mentioned that they will have to be tied in to the concrete floor due to it being a mining area in the past.

I think I should have stuck to my original lean to idea

 

[Thermo]

length x depth x width gives you the volume (do it in metres)
a jumbo bag of ballast is normally half a cubic metre
so roberts your mothers brother!