No wood below grade. Do luxury vinyl tile. But without a vapor barrier under the slab itself, and a permimeter waterproofing system, you WILL have moisture under it. Not much will warm up a basement slab floor without insulation under the slab other than adding radiant heat. At least vinyl will be a tad warmer to the touch and you can pt rugs on top.

Hmm, I hadn't considered that. Now I've heard engineered wood is fine below grade, no? I wish I knew if the floor was poured with a vapor barrier. Any way to tell?
I also considered cork but having 3 kids, a dog, and lots of guests, I'm afraid the floor with be scratched to pieces.

Look at Hydroment's Ultraset. It's a trowel-on membrane. An excellent adhesive, a moisture barrier, and a crack isolation barrier all in one.

For the areas that will have RFH, you can use the Ultraset as an adhesive to set something like Cerazorb, a synthetic cork. Some folks do use 1/4" or 6mm thick true cork on the slab to act as a thermal break, just make sure it's not a low-density cork and that it's recommended for that purpose. There are RFH websites that sell a proper cork product.

The RFH can then go over the Cerazorb/cork.

OR you can use the Ultraset to adhere RPM mats (or equivalent) to the slab and install your RFH over that. RPM mats will act as a therma break, even though they have a negligible R-value. RPM mats are lugged mats, the lugs act as anchors for weaving RFH wire.

While the RPM mat has little R-value, cork on the other hand has an R-value of about R3, so you'd get roughly R 0.75 from a roll of 1/4" cork.

In the areas that won't get RFH, you can use Ultraset to adhere 1/4" cork/Cerazorb to the slab, then install a floating engineered flooring over the cork.

1/4" thick Wedi board can also be used instead of cork/Cerazorb, etc.

All those are low-profile options. You'll get a bit of a thermal break but very little improvement in R-value. If you want more R-value, look at sheets of XPS. XPS comes in 4' by 8' sheets and is about R5 per inch.

As you can see there are numerous ways to get this done. Some products have certain advantages over others.

Look at doing DriCore. But, if you have a moisture problem in the room, wood will not be happy. If you have a flood incident, it will be toast.

One simple test that you can do to see if your slab is moist is to tape down some clear plastic film on the floor. 6 mil film preferred, a 12"x12" square, in various parts of the room. Use the real tape used to seal ducts, not "duck tape". Wait 48 hours. View whether or not you have condensation under it. If you have condensation, you cannot put wood on the slab. You can do some of the methods recommended above, but if there is a lot of moisture, I'd rethink the project entirely and look at whole home moisture management through exterior wall waterproofing management.

Thank you all! I will do a test on the slab and will look into all these options. Very good information, I appreciate it.

I had wanted to do the cork on my slab first floor before or after the moisture barrier but the flooring store told me this furry stuff they used was warmer than the Floor Muffler I used last time. Since the wood board I used this time was only 3/8th thick Brazilian Cherry hardwood flooring, the floors is colder than my prior 1/2" thick Brazilian Cherry Floors and I am so upset. I should have found another store that would have helped me make my floors warmer. I wish this thread was up before I did my floors.

Hi,

I am looking into these possibilities and had some questions.

Hippy, are the sleeper wood? Let's say in case of leak or water damage, will it be more damage to the floor because the underflooring (sleepers) and subfloor would get wet?

Live-wire-oak, would I do the flooring over the Dri-core or would I still have to lay subflooring over that?

Mongoct, can the engineered floor be floated over the XPS? Is the advantage of using the cork over XPS the thickness? Is the cork a vapor barrier as well? Or the Ultraset is enough? Also, what if the slab isn't level? I'm not sure on this yet, there is currently carpet over it that we need to pull but can't do yet.

We have decided to add a smaller secondary furnace to the lower level to help with overall heating, so I suppose I'm mostly concerned with the thermal break and no cold feet.

Susanlynn I'm sorry that happened. I know nothing about subflooring and never even considered this issue until now. I have a steep learning curve.

Also be careful since the cold is coming up from the floor making my room colder and I have to keep raising my forced hot air heat making it dryer in the room with more of a gas bill. I have to run the humidifier all day and it is so dry in my room. I can't believe that the extra 1/4th of wood with the floor muffler is warmer than this slightly higher R rating floor vapor barrier with the thinner board. I had posted in the flooring forum if the thicker board mattered but I was told only the real wood on top mattered. OK, flooring experts must tell people the thinner the board over concrete floors, the colder the floors. I have Raynaud's and even with two pair of Merino Wool Socks and Merrill Thermal Boots on, my feet are cold and my legs are cold. I did tell the store that I had a medical condition and needed cork also on the floor or something to make the floor warmer and I was told that would be overkill since this stuff they were using was so warm. I had to put a carpet in front of my client's feet as they were complaining. I had to buy heated foot rests. I am very upset and wish now I took the time out to find a store to help me and did not do my floors until the winter started to remind me how cold they get. Upstairs I have plywood floors so the floors will not get as cold but I am going to be sure they are not so cold before replacing my very old wall-to-wall padded carpet.

Susanlynn that is amazing, I wouldn't have thought it would make such a difference. My mother has Raynaud's so I understand what you are saying. My last home had heated concrete floors and they were the BEST. If I ever built a home it's absolutely what I'd do.

Thank you happyallison for understanding. Now I wish I found a way to have radiant heated floors or a few layers between the concrete and the wood. If I knew the floors would be almost as cold as the tile floors in my kitchen, I would have installed wood that looks like Tile with radiant heat underneath. It was just difficult to install radiant heat with a forced hot heat system and expensive but it would have paid off on heating bills not so high. So cold! Glad I could share so others will realize the thickness of the plywood part of the engineered wood DOES MATTER if you don't want higher heat bills and to be freezing cold if you live on a slab concrete floor.