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Basement Subfloor

What Are Your Options With Basement Subflooring?

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basement subfloor

BARRICADE™ Flooring System

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Poor basement subfloor. It has so many jobs at hand. Unlike above-grade sub-flooring, basement subflooring has to do all of the usual subfloor things and more. Here is everything:
  • Provide a flat, level surface for the finish flooring.
  • Keep moisture at bay.
  • Provide a thermal break (i.e., insulation).
  • Be able to dry out in the event of flooding.
  • Not be too high.
  • Not cost too much.
What does all that mean? We're taking it as an article of faith that the basement subfloor will provide a flat, level surface for the finish flooring. It simply needs to do that.

Keep in mind that you don't even need a subfloor if you don't intend to finish your basement. Subfloors only come into play when you want to expand downward and make your basement a warm, livable space. In order to install better, warmer, nicer types of flooring, such as engineered wood or laminate--as opposed to the conventional basement carpeting or tile--you definitely need basement subflooring.

Basement Subfloor Considerations Explained

Moisture.

Even if you do not expect catastrophic events such as flooring, moisture can and probably will invade your basement. Since basements are nothing more than holes in the ground lined with concrete, and moisture is pervasive in the ground, this moisture will gradually work its way upward through concrete basement flooring and will condense.

Another big issue is height. Yes, you can build a 12-inch high basement subfloor and stay dry above everything, but basement ceilings tend to be low. Eight-foot basement ceilings are rare, and seven-footers are more the norm. Thus, even an inch or two in your subfloor will make a noticeable difference.

Following are several options for your basement subfloor, and we are not giving any of these preferential treatment. Also, note that the list of materials is shown in the same way that you would see these materials in a cross-section, not in the order of stacking them.

The vapor retarder that we mention is 10 or 15 mil sheeting. The sheeting that you find at a Lowe's, The Home Depot, or hardware stores tends to be thinner, so you may need to hunt down this sturdier sheeting. The plywood is 1/2 inch exterior grade kiln-dried plywood. Finish flooring is the top-most layer, the flooring that you will walk on.

Option #1: 2x4s and Plywood

This is the traditional method of building a basement subfloor. Height is the problem with this method, as it employs a system of 2x4 sleepers.
  • Finish flooring.
  • Plywood fastened to the sleepers.
  • 2x4 sleepers installed on center every 12-16 inches and fastened down, with rigid foam insulation 1 1/2" thick placed between the sleepers.
  • Vapor retarder.
  • Concrete basement floor.

Option #2: Floating Plywood

Not my favorite subflooring option, as the only barrier between the concrete and the plywood is plastic sheeting. But it's an easy subfloor to lay down.
  • Finish flooring.
  • Plywood.
  • Vapor retarder.
  • Concrete basement floor.

Option #3: Rigid Foam Insulation

A nice option because the foam insulation provides an excellent thermal break between concrete and flooring.
  • Finish flooring.
  • Plywood screwed down through the layer below.
  • Rigid foam insulation - 1 1/2" thick.
  • Concrete basement floor.

Option #4: Specialty Subflooring Tiles

Some companies sell all-in-one subfloor modules. BARRICADE™ is one such example: 2' x 2' x 1.125” tiles with OSB wood on top and closed cell polystyrene insulation, XPS on the bottom. The chief advantage is the thinness of the product.
  • Finish flooring.
  • Subfloor module (BARRICADE™, Subflor, etc.)
  • Concrete basement floor.

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