Concrete insulated workshop floor advice?

[caravanboy]

Hi,
I am hoping to build a small workshop inside an old barn. The barn floor is currently soil as it was an old potato store. I would like an insulated concrete floor. I've searched the forums for general floor construction advice but can't seem to find anything specifc. I think I need something like this (from the bottom up) but I'm not sure on the specifics:

Hardcore/aggregate - how deep?
Sand blind - an inch thick?
Damp proof membrane - any particular type?
Insulation (Kingspan) - 100mm?
Concrete - Will four inches be thick enough, I may have a heavy lathe?

Other questions:
1) Do I need to put steel bars in the concrete to strengten it as it may be used to store small vehicles (e.g. car / tractor) in future?

2) Will Building Regs apply if this is a workshop constructed inside an existing building?

3) Do I need a screed on top of the concrete?

4) Two of the walls of the workshop will be existing barn walls, two will be new walls inside the barn [it's in a corner of the barn]. So, do I build the new walls on top of the new concrete floor, or do I build them on their own concrete foundation and then lay the concrete floor inside the four walls?

Any advice appreciated.
Thanks.

 

[ladylola]

Your construction approach sounds about right.
Your hardcore I'd go for something like 100-150mm and whackered down, sand yes about an inch although I may be inclined to deepen your concrete if it's going to be a vehical workshop maybe 150-200mm thick. If in any doubt I'd say overengineer the floor and put in steel mesh too.I wouldn't bother with the screed for a workshop to be honest just a float finish to the concrete would be fine.
As to the walls if they are to be in brick or blcok then I'd use seperate footings and concrete up to them , but couldn't you just build them in studdwork on top of the floor slab?