Floor structure on uninsulated concrete slab

[blazern]

Today I have an uninsulated concrete slab in part of the outbuilding. How can I most easily insulate and lay a new floor?

I'm thinking of placing an age-resistant plastic on the concrete slab, building a wooden floor frame without contact with the slab/plastic. Insulate, chipboard flooring, and then the floor.

Right/wrong?

What dimensions do I need for the floor frame? About 3 m span at most.

 

[Oldboy]

Do you have moisture in the concrete slab?
If you do and lay plastic, the moisture will seek its way up into the walls, unless they are 100% moisture-proofed down against the slab.

You can find out by laying down about a square meter of construction plastic on the floor and sealing/taping the edges. Leave it for a few days. If it is moist under the plastic, you have moisture in the slab.

 

[blazern]

Good question, what should I do if it turns out to be damp?

It has been an old laundry room from the early 1900s, the wall studs and the frame seem to lie directly against the slab. No noticeable moisture on the wood yet after 100 years...