Install floor on concrete slab

[Rick Varadi]

My cottage is built on a concrete slab ,,keep in mind a 2x6 sill plate,, I want to use 5/8 sub floor but insulate it under neath with rigid insulation,,but hav to have clearence for my door swing,,,I'm thinking I need to strap the floor first which may impede my door swing after the subfloor is installed ,,,,any ideas or options I might have?

[HayZee518]

If you use the type of insulation used under exterior vinyl siding and glue it to the slab, it may be a way out. it is foil faced on both sides and probably 5/16" to 3/8" thick. with 5/8" on top of that its still under 1 inch or even with 1 inch.

[Rick Varadi]

should I leave the 5/8 sheathing floating then?? or glue it to the rigid insulation?

[pushkins]

I understand what you want to do but I'm lost in translation.
You want to "strap" the concrete floor ?
There is no sill plate on a concrete slab. The house is built on the concrete and the doors threshold should sit directly on the concrete.
When was this house built ?
5/8" subfloor gives almost the same insulation level as 1/4" foam.
What type of floor are you looking to install?, carpet, laminate, tile ?
No matter what sort of floor you want to install the 5/8" sub floor your adding must be attached to the slab.
If you are trying to put foam under the 5/8" sub floor then you have even bigger problems as you cannot glue the foam to the concrete and then the foam to the wood.

The biggest problem I see with your idea of rigid insulation under the subfloor is the small fact that over time the foam will compress, especially in high traffic areas due to traffic and temperature and this will lead to height changes.

No matter what you do the 5/8" subfloor must be attached to the concrete and this means glue or Tapcons set every 24" and 12" on the edges of each sheet (man what a sucky job that will be).

You might want to consider glued down laminate flooring or even glued down solid flooring.