How Thick and Also do I Need Rebar for Foundations for Double Skin Single Storey Building Drainage pipes, concrete, footings and foundations. Post your questions and find answers here

[theskid]

hi,
I'm Currently in the process of setting down the foundations for a 1 storey double skin building (engineering brick outer 100mm cavity with kingspan insulation then for the inner skin either concrete block due to its fixing strength or thermalite block for its thermal properties (a bit worried if it will hold up shelving etc though))
the roof shall probably be corregated steel ,a slightly angled flat roof with wooden roof struts as to fix the steel roof to
my question is are the following correct
trench is 24" width ,the depth varies from 300mm to 400mm, as I have dug the topsoil to reveal the clay and tried to knock wooden stick down for which I can not get past the 6" recommended
do I need rebar? as a groundsmen from work has advised me to use a
10mm rebar ,if so at what height and were within the concrete to I place it?
do I overlap the corners and also I have been told to leave 3 "gap around the edges?
I have been told a 6" depth of concrete strip fouddations will be sufficient for this structure? (which will not exceed the golden 2.5metre rule)
the structures dimensions are 7.72metre length by 3.44metre width

[welsh brickie]

it should be on the plans, I am assuming you have planning consent.
The concrete foundation thickness depends on ground conditions, and the building inspectors recommendation.
But standard is 225mm thick, rebar mesh can be cut in lengths and laid in the foundation, laid on reinforcement stands that keep the mesh off the ground. Also keep it away from the edges by 50mm so that the concrete surrounds the mesh.

[theskid]

No plans
This is purely a diy project
With help off others
Planning permission not required as it's within the permitted 30m2 and 2.5metre height
And it's not to be lived in
Its is within 2m boundary but will be built of non combustible materials as this it's ok via planning portal
Also i have contacted local building control
And described what I'm doing and they have told me to go ahead as no notifications required and doesn't fall under building regs
Although i will be sticking to the regs

I Have been told that 150mm thick footings on the decent clay will be sufficient with rebar
Is it worth doing the extra thickness
225mm our odds this overkill as on a budget?

[welsh brickie]

planning permission is not granted for a hobby shed, in my area, different counties have different rules, that's why I asked.
150mm thick concrete does not require reinforcing, If your unsure about the ground conditions go the extra mile.