Is Underlayment Needed with a Cork Floating Floor?

Q: Is a cork underlay needed if the cork floor, is going over a cement subfloor? We have turned a very large crawl space into 2 rooms and a bathroom and plan on putting floating cork flooring down (not in Bathroom), but are not sure if an underlay is needed, since sound proofing is not an issue. Is the additional insulation needed/worthwhile, since we live in Richmond Va. and it does not get that cold.
Thanks
Greg Lloyd
A: When installing a floating floor over concrete there are a few things to keep in mind. First of all you MUST have a vapor barrier. You will also want to ensure that your subfloor is flat and smooth. This could involve using a self leveling compound in areas where dips may have occurred over time.
The Cork you are looking at does have a cork backing, but I would highly suggest adding a 3mm cork underlayment to ensure you get maximum lifespan from your floor. You could use other underlayment types, but thicker underlayments (such as the 6mm Cork) would normally be used for added sound suppression, which your not focusing on here. Cheaper underlayment, such as the foam based combo underlayments are not as dense as Cork and will make the flooring feel springy under foot.