No matter how nicely the rest of the basement is finished, if the floors are cold and the room feels damp, nobody is going to want to spend much time down there. It's a common problem in a finished basement because concrete floors continually release moisture (making a basement feel damp) and they act as a conductor for the cold from the ground under the foundation. In the past, people have tried to address the problem by laying down a wooden sub floor before installing their basement flooring, but over time a wooden subfloor that is in direct contact with the damp concrete will degenerate. The wood doesn't do anything to prevent moisture, so the room will still feel damp.
The Solution - Floating Subfloor Systems
Fortunately, the construction industry has come up with a solution for cold, damp basement floors, floating sub floor systems. While there are numerous manufacturers of these systems, they all work essentially the same way. They create a moisture proof air gap between the concrete floor and the basement flooring.
They are usually built from either plywood or oriented strand board (OSB), bonded to a corrugated underlay in 2' x 2' tongue and groove panels that fit tightly together. A floating sub floor keeps a basement floor warm and comfortable.
How Do They Work?
The underlay (made from heavy duty polyethylene or styrofoam insulation) creates an air gap under the plywood surface (and above the concrete) so the wood never touches the concrete. As a result, the wood won't get wet and rot over time. Plus, the air gap allows air movement under the floor that will dry any moisture coming up through the concrete and at the same time the moisture-proof underlay acts as a barrier to stop dampness from rising into the finished room above. So, there won't be any dampness and no musty odors in the room. With the basement floor now warm and no odors or dampness in the air, a finished basement with a floating sub floor system becomes quite livable.
Are There any benefits?
Manufacturers claim the engineered wood floor won't warp, split, or peel. The panels are alleged to be strong enough to support heavy furnishing or things like a treadmill or a pool table, too. Most back up these claims with warranties of up to 25 years. You can install carpet, laminate, engineered flooring, ceramic tiles, or vinyl tiles on top of the panels. (Vinyl tiles require a 1/4-inch plywood sub floor while ceramic tiles need a base of cement board.) The floating sub floors are comfortable to walk on, since the soft underlay has a little "give" to it and softens each step.
What Are the negatives?
The panels must be installed on a level surface, so the basement floor must be leveled beforehand. It will be difficult in basements that don't have much head room since the panels are about 1-inch thick.
Over all, a floating subfloor will help make your basement a comfortable living space.
Murray Anderson is an experienced freelance writer whose work has appeared on numerous web sites, as well as in newspapers and books in both the U.S. and Canada. He is regularly cited as an expert on home related topics and is a regular contributor to DoItYourself.com.