Hello, 

I have a slab on grade floor that is way out of level.  It’s an old house and we plan on a bigger remodel in the next 5 yrs or so, so pulling out/ fixing the slab isn’t gonna happen right now.  We are in Northern CA, so it never gets too cold.

I plan on the xps over slab with 2 layers of 1/2 inch ply or maybe on 3/4 layer for an engineered floor or laminate on top.

https://www.finehomebuilding.com/how-to/qa/finishing-a-basement-floor.aspx

Question is, I need to level the 9 x 12 ft room as much as 3-4″ corner to corner.  So, XPS and them lay sleepers on top? or frame it like a deck and put the XPS in between the sleepers?  The floor is dry, plastic taped over the floor results in no moisture.  I was going to go without a vapor barrier so the floor can breath.

thoughts on best approach.  self leveling cement is out of the equation too.

thanks

-Russell