A Subfloor Adds Room

For those homes with a concrete floor area there is living space waiting to be used just by adding a subfloor. Whether the area is a basement, garage or utility room, by covering the surface with the right materials the homeowner can extend the square footage without doing major renovations.

What is a SubFloor?

Because of the very nature of raw concrete it does not make a good living surface. Unsealed this floor is porous and allows moisture to pass through its mass. This is why few solid hardwood floor manufacturers will warranty a product that is installed on a concrete floor. A subfloor is a solid barrier that seals our moisture while presenting a solid, stable, humidity-controlling surface that will allow the homeowner to install almost any type of flooring. Some foam-backed products are described as "self-leveling" and compensate for irregularities in the concrete. In essence, a subfloor is a stable platform for as flooring product.

1. Pressure-Treated Wood

Since the walls of most homes are built with a wood-frame system on 16" centers a simple subfloor can be built in much the same way:

• Plan: Draw a plan of the area determine the amount of 2" by 3" pressure treated "sleepers" and 6 millimeter vapor seal. (Allow for lengths for the perimeter.
• Seal: Roll the vapor seal on the concrete and tape the joints and edges with drywall tape.
• Perimeter: Lay the sleepers around the edge of the room and fasten to the wall studs. If there are no wall studs rent a hammer set and drive fasteners into the concrete.
• Frame: Mark the vapor seal in 16" widths and cut-to-fit the pressure-treated sleepers. The sleepers are toed-in to the perimeters.
• Substrate: Now plywood can be screwed down to the sleepers.

2. Insulated Subfloor

In many parts of the country a concrete basement or garage floor can suck the heat out of a home. By insulating the subfloor a homeowner could save hefty oil or natural gas bills. The planning includes high-density, expanded-polystyrene, rigid-foam sheets. With an R-4 insulation rating this type of sheet not only provides a great base for a subfloor but keeps out the cold as well. The high-density factor means that a tongue-and-groove floor sheathing can be glued right to the surface without framing.

As with the other flooring the dimensions of the area must be taken as the rigid foam sheets are expensive. They can be glued to a dry, concrete surface with a construction-grade adhesive and the cracks then sealed with a drywall tape. No vapor seal is needed.

3. Subfloor Tiles

One of the newest products is also one of the easiest to install. Subfloor tiles are manufactured in two-feet by two-feet, tongue-and –groove squares which literally snap together for a full floor in less than an afternoon's work. One type offers a foam backing that offers R-3+ for a warmer floor. Combined with a laminate floor or carpet and the R-value goes up. The foam undersides are channeled to allow moisture to seep toward the drain.

Another subfloor tile manufactured for slab-on-grade installation has a plastic underside that allows air to move underneath and dry any moisture that may accumulate. The air space created allows any water vapor pressure both above and below the concrete to equalize and prevent it from going any further into the floor. The basement stays dry and there is a thermal break with the air space.

For more information on these amazing floor tiles, and how they can be installed, consult our Contractor Directory or simply post your project online.

Kim Kinrade writes for renovation, travel and news sites. When he is not doing this, or renovating old houses, he finds the time to write novels.