If you have a cement floor, you might want to think about adding a floating subfloor before the top covering. Cement can keep the floors cold because it does not retain heat. Plywood, or OSB board, does make a great subfloor over cement. Here are a few tips to help you install your floating subfloor.
Keep Cement Clean beore Laying Plywood Subfloor
If there is any type of dirt, debris, screws, nails, or even a liquid, it can cause major damage to the plywood subfloor. Make sure you thoroughly clean the cement floor before you attempt to add a subfloor.
Acclimate the Wood Before Installation
There is always a period of time when the wood needs to acclimate itself to the room it is going to be installed in before the actual installation. Some wood require more time than others, but letting the plywood sit in the room for at least 24 hours will keep it from shrinking and expanding enough to ruin your floor.
Check Moisture in Cement
Cement does retain some moisture for a long period of time. Check the moisture levels in the concrete before laying the floating subfloor. You many have to use a water barrier.
Lay Floating Subfloor
As you lay down the 1/2 inch plywood, or OSB, keep 1/8 inch of space between each sheet.
Source: www.DoItYourself.com