Workshop base layers - is this a good plan?

[DaKid]

Apologies if this is a duplicate, but I have tried searching for exactly my situation without success.

I have an existing pre-fab shed on a 6m x 3m concrete slab but it's rotting and has been flimsy from when it was first built. I'm looking to replace it with a custom build (partly so it's better, partly because I just want to do it!), but could do with some advice to confirm what I've been researching regarding the construction of the floor especially. It will probably be split internally into a workshop area and a general shed-type area (for storing bikes, garden tools, etc).

On top of the slab, I'm intending to lay 2x2 battens with a strip of DPC material stapled to the underside, with OSB on top of that and then PIR boards on top of that (with tape to form a vapour barrier) with chipboard flooring and then finally laminate, to be more easily replaced than the chipboard when necessary.

Does this sound like a sensible way of doing it?

Do I need a breathable membrane either above or below the OSB?

 

[Odds]

A membrane below would be better - how much ground clearance will the floor have over the concrete base?

 

[DaKid]

I guess 2 inches from the 2x2 battens, if I’ve understood your question correctly.

 

[Odds]

A two inch gap is okay, but why bother with a concrete base, in that case. It won't support the floor, will it?

 

[DAZB]

I would beef up the 2 x 2 studs to at least 3 x 2 or even 4 x 2 as it would be much more sturdy given it is a 6m run and therefore more capacity for insulation in the walls. It is better to do it now rather than wish you had done it later.

 

[DaKid]

A two inch gap is okay, but why bother with a concrete base, in that case. It won't support the floor, will it?

The concrete base is already there!

I would beef up the 2 x 2 studs to at least 3 x 2 or even 4 x 2 as it would be much more sturdy given it is a 6m run and therefore more capacity for insulation in the walls. It is better to do it now rather than wish you had done it later.

The studs will be 2x4. It’s just the battens underneath that are 2x2s.