Laminate Flooring on Enclosed Deck

[prashster]

My uncle has a sunroom that is basically an enclosed deck. The floor is slatted deck boards, open to, and elevated from, the ground.

He wants to put a finished floor on there. What are the best options?

I suggested a polyethylene barrier over the deck, followed by rigid insulation, then possibly a plywood underlay and finally laminate flooring. Would that work?

Would cement backerboard be a better choice?

He received counsel from a flooring guy that laminate is a bad choice in that room because of the climatic changes (it's unheated and uninsulated). But if you can do laminate in a basement, why not in such a room? He'd insulate the floor...

[Bob NH]

A basement is very constant temperature, so there is very little expansion and contraction.

I would consider some kind of carpet. That is very tolerant of things that would damage laminate or other smooth finish floors.

[prashster]

Thanks, Bob. What's the best way to insulate the floor?

[Bob NH]

Thanks, Bob. What's the best way to insulate the floor?
First, figure out how much thickness you can stand.

Then, I would used a layer of rigid foam, with waterproof facing on the top side or both sides. It needs to have a layer of material that will prevent punching through.

You can use foam padding under the carpet which will insulate some, if you want that kind of carpet. If you use a more casual carpet without padding, then the foam is the best insulation and you probably need 3/8" of decent plywood for underlayment. I would not rely on 1/4" luan to resist punching a chair leg through to the foam insulation.