Hi. The big box store had some bamboo flooring on sale, so I bought some for our kitchen and powder room. It's solid bamboo in the "horizontal" form. We thought we might put some 1/4" or 1/2" cork sheets down as an underlayment for both thermal insulation and to make the floor a little more easy on the knees. Has anyone done this? Is cork ok to put under bamboo? Any comments would be appreciated. Thanks.

Done it many times. Even seen genuine linoleum glued down over cork sheet underlayment. You have to adhere the underlayment down and then adhere your flooring choice to that. Just be aware that the slab should be tested for moisture emission amounts and any issues with moisture need to be mitigated. Or, you can just use an adhesive that forms its own moisture barrier or one of the two-part systems that include a liquid applied moisture barrier and then a compatible adhesive. Also, with glue down cork you must use the recommended adhesive. You would run your proposed installation system past the technical folks at the cork tile manufacturer. The adhesive specified for glue down cork is almost always a flammable contact type. Then, you finish your cork tile, if the unfinished type, with a commercial quality wood floor finish. That is a whole other discussion.

@Tyler G - all cork floating floors have an integrated underlayment. The thickness will vary between price points but they all have them. The issue is the wonky subfloor. That's your biggest issue. To reduce the effects of this problem, you would want to use the 1/4" cork to get rid of *SOME of the issue. You will still have some movement in the floor (a snick of bounce when you walk over a low spot) but not as bad as when laying a floor straight over top. To get the most benefit out of your situation, the cork floating floor + 1/4" underlay will offer the "most for the least". That is to say the most comfort/acoustics/price advantage/longevity for the least amount of work/disturbance to your rented home. You can't do the work on the subfloor that is needed (it really is needed if you want the floor to live 20+ years). So you have to do as much as possible to reduce the effects of the wonky subfloor. And that means investing in a decent, rigid underlayment like cork. Even though the cork sheets are flexible, the cork itself is rather rigid. It doesn't "squish" down very much (it is actually rated for porcelain tile installation). That means it will even out the wonky subfloor - just enough to get you a cork floor that should live 15 years or so. Please remember to use transition strips at all doorways. This is another way to ensure your floor will get you more than a decade worth of life.

Just want to chime in here for those looking for the more "green" option: Green Building Supply sells a proprietary chemically-sensitive version of QuietWalk without the biocides/fungicides that make up the "antimicrobial" characteristics of conventional QuietWalk. (I confirmed this with MP Global.) I don't work for Green Building Supply or receive any commission or anything else. Just passing that along for those with chemically-sensitive household members! :) And @SJ McCarthy, I was just about to give up on QuietWalk and go with thin foam FloorMuffler Ultra Seal, since that's the only underlayment my local flooring store recommends (at 59 cents SF, hmm). Then I saw an old thread where you gave big thumbs up to QuietWalk. Several flooring stores told me FloorMuffler can't be beat for sound absorption, but my skeptical self wonders if it's more a matter that it's a higher profit margin for them vs. QuietWalk. I need to write a check for my flooring today---any last words of wisdom on QuietWalk vs FloorMuffler (over concrete slab, single story)? Thanks! @jfcwoodd too