Treated sleepers would be installed 16" OC by means of pl400 and mechanical fastening such as a Ramset. Insulate between the sleepers. Check on vapor barrier before installing subfloor. I would use 3/4" plywood for deflection purpose when laminate is considered. Also make sure the choice of laminate can be used below grade.

We do not want any wood in contact with the concrete (vapor barrier is under the slab), so we would prefer a solid layer of insulation. Do you have any suggestions for this? Thank you!

i hope you're joking. Subfloors must be structurally sound for installation. Putting plywood over insulation is not an approved method simply because insulation is not an approved structural material. You can't change that, no matter how much you want to.

I am absolutely not joking. This is actually a recommended method: http://www.finehomebuilding.com/how-to/qa/finishing-a-basement-floor.aspx

ETA: I only asked on here to see if there are experiences with this method or other ways of doing it. We don't really have the headroom for 2 layers of plywood. We would like to keep the floor height at 2 inches.

I was hoping your link would be beneficial. However, what does installing glued down cork flooring have to do with installing Mannington laminate?

The type of flooring actually doesn't matter. Here is another link: http://www.greenbuildingadvisor.com/sites/default/files/The%20Stay-Dry,%20No%20Mold%20Finished%20Basement_FHB169.pdf

I hate to point out the obvious, but the manufacturer's installation method is all that matters. So the argument will be with them, so good luck with that theory.

i predict should you move forward against the manufacturers installation instructions, you will be back blaming someone for a botched job It happens all the time on these forums

That is why I am doing research beforehand. Unfortunately, we cannot just install the laminate on the concrete. It needs to be insulated first.

Given the compressibility of the styrofoam I would think that it might cause the laminate floor to fail prematurely. It might be worth asking the laminate manufacturer whether they'd honor their warranty in that situation. My guess is their response would be: "no way, no how."

I remember reading about a insulating flooring underlayment on a tiling forum a while ago. I looked it up and I believe it was a product called Wedi board which might be a better idea since it is actually designed to be used under floors.

Thanks for the Wedi board suggestion. I will look into that. I didn't think the compressibility of the foam (15 psi) would be an issue since it won't have any load bearing walls on it and it is often put under concrete slabs.

Disaster waiting to happen. If you properly insulated the slab, then it should be plenty warm enough for traditional laminate. Now, as to laminate being a good choice below grade, I wouldn't do it. Most laminate manufacturers agree and wouldn't warrant it either. Vinyl or tile below grade. Period.

You can purchase compression grade rigid insulation for your type of project.

@housebuilding126, What did you end up doing?

Concrete slabs weighing many tons are poured directly over rigid foam. You may want to use a sub floor over the rigid foam before installing the laminate flooring. See: U.S. Department of Energy, Building America Solution Center, Rigid Foam Insulation Installed over Existing Foundation Slabs

You need to make sure that this is an approved sub-floor for the laminate by the mfg. first. But a floating sub-floor can be used by using two layers of 3/8" or 1/2" cdx 1, screwed to each other. This system is usually installed over sound proofing material. You just need to make sure your foam insulation doesn't get crushed with all the weight on top of it. You may want to look into a 1/2" rubber material instead. Make sure it's mfg approved substrate system.

I'd go ahead or hope you already did with two layers of wood over the rigid foam board since my way of placing the foam board on gravel would be considered much worse but OK for my old shed that I want to insulate without mixing bags of concrete first. A couple sheets of good thick plywood on top should be good enough for my needs and get it done. I would need to use glue since nothing to nail into before someone points that out, but I do have gravity in my favor.

Dricore has come out with a eps foam to go on basement floors and it has a 3500 psf. They are said you can put flooring right on top of it! With that as a starting piont, if you were going with xps foam and you were to put down 30 psi or greater it should be ok, I would think... any thoughts.. the dricore product is only available in the states, not Canada.

DriCore is available in Canada. The 'availability' of stuff crossing the boarder is a big issue. The availability of wood products is another issue.

3650 PSF is equal to 25 PSI..... Their dricore products are just massively overpriced, at least in the US they are.

I think it is better to put down a foundation wrap (DMX), then 1" XPS foam (25-30 PSI).

Assuming that the floor is flat, you could probably get away with putting flooring (with a membrane) directly on top of it. If your floor isn't flat, you probably will need a dedicated subfloor.

I'd also be sure to use some kind of flooring that is somewhat rigid and install it perpendicular to the foam boards, so that if the foam boards do try to lift or sink, the flooring will add some rigidity to prevent it from mattering.

I used 3/4" xps, 25 psi with 2 layers of 7/16" OSB cross-linked screwed together and applied an lvt over for 5yrs now with no problems, Make sure to the OSB is fulling acclimated and it won't warp like plywood.

I know people are saying DriCore is expensive but by the time you add up the material costs to use regular pink foam, OSB over it and all the labor, DriCore has to be cheaper...