Your choices for flooring that would be certified for glue-down to concrete below grade is probably the limiting factor.I know you can do so with BR111, I put one such in a basement several years ago. It is not fun. It looked very good, however.

Casey

I agree, any underlayment is going to work more for a "cushion" and sound dampening, nothing for head retention. If the concrete gets cold, floating as opposed to glueing down wont make a difference.

Now there are underlayments that you glue first and then glue to planks to the underlayment. Many options.

Floating the floor is going to require a bit more attention to making sure the concrete is flat. Glueing will still require a flat surface but not as much as it would for floating.

While most engineered is certified for glue down or floating on slab ON grade, very little is certified for use below grade except as floating. Which will generally not sound or perform like glue down.

Read the manufacturers documents carefully. Understand that the best results will be achieved by a separate applied waterproofing membrane and then a polyurethane glue. Which adds up to quite a bit of ancillary costs beyond the wood itself.

I'm not a huge fan of floating floors but it's probably the better option in this case. Poly film under the foam layer is an inexpensive moisture barrier. If you decide to glue down, do calcium chloride tests to determine the moisture level in your concrete in various areas.

Also I'm worried about gluing to concrete vs. wood subfloor. Is gluing appropriate in this application?

Absolutely not. Those floors will need replacing quickly guaranteed. You don't want wood meeting concrete. At a minimum you will need a vapor barrier between the floor and concrete, and you wouldn't be able to glue this way. I guess perhaps if the engineered wood had a vapor barrier backing..

The floor you have chosen also has to be able to float, if you chose one that requires glue down or nailing, that wont work either. Normally the click lock types are those that can be floated.

If you really want a warmer floor in the basement, an underlayment alone wont do the trick. Best option is to insulate the floor with XPS sheet foam topped with a subfloor secured with tapcon screws (predrill before screwing), then you can do whatever flooring you want.

Personally, I would want to make sure you don't have a moisture problem with the concrete floor before you do anything. Tape down plastic at various locations and see if moisture builds up underneath the plastic. If it does, then you need to first apply a waterproofing solution such as watertite so that moisture does not accumulate underneath the vapor barrier and cause mold.

"you could consider radiant heat."

I don't think many are aware of heating pads instead of a full blown radiant heating system. Of course you'll have to float the floor.

Here's one...http://warmfloorsource.com

Then you could glue down a 3/4 inch engineered. The thickness should insulate pretty well.

3/4 inch engineered

OK, so my floor is VERY unlevel even after grinding down there was a significant difference in areas which is why they wanted to glue it. I see floating won't work. They are using Bostik's Best urethane to vapor barrier and glue it. I hope this is appropriate. Honestly we will have major teeter tottering in areas if we went with floating. It was demonstrated to me. :(

Why dont they get self leveling concrete and level the floor first.... Prep work is just as important as doing the floor.

They can but it apparently (?) is cost prohibitive due to the expanse of over 700 sq ft. ?

They cant do a feathered patch job in the areas it takes a dip? All they need is a straight edge to find where the problem areas are so they can properly prep the space to accept the floor they plan on installing. I feel ignoring the prepwork will transfer through to the finished floor and you will notice it.

If it ain't flat enough to float, it ain't flat enough to glue. The requirements aren't any different. Best ain't good enough below grade either. Needs a moisture test first. And probably 250 or even 261 first, then Best. Or Greenforce applied with the thick trowel.

Yeah, it's more expensive. But so will be doing it twice when the first attempt utterly fails.

I will check with them, thank you all!

I sure wouldn't want to see an un-happyallison.

As the old adage goes..."your final floor will only be as good as the subfloor"

In other words, you may need this if it's not done right.

Your decisions for ground surface that would be guaranteed for paste down to concrete underneath grade is most likely the restricting component.

Those that don't think that engineered wood floors will stick to concrete need to read the experiences of a guy who's had to remove some.

"Also I'm worried about gluing to concrete vs. wood subfloor. Is gluing appropriate in this application?

Absolutely not. Those floors will need replacing quickly guaranteed. You don't want wood meeting concrete. At a minimum you will need a vapor barrier between the floor and concrete, and you wouldn't be able to glue this way. I guess perhaps if the engineered wood had a vapor barrier backing.."

The National Wood Flooring Association approves of gluing engineered wood floors directly to a concrete subfloor.

Thanks for the link lots of good info there, but the slab needs to be dry of course. I personally do not like untreated wood to touch concrete, but to each their own. You could say the glue does not allow the wood to touch the concrete directly though. :) I always worry about mold/rot with a concrete wood junction and with wood floors there is the additional problem of expansion and buckling with moisture.

Chapter 5 B. 3. If a slab tests too high in vapor emission to glue a floor down, consider using a vapor retarder type product, installing a vapor retarder and a plywood sub-floor or using an alternative installation method