how to extreme

Insulating a Basement Floor

Basement, Construction How-To, Energy Efficiency, Insulation and Energy Conservation October 20, 2010 Matt Weber

 By Matt Weber


Insulate your basement by installing a floating subfloor.





Is your basement nothing more than an unfinished storage area? That’s the case with many homeowners who consider their basement to lack the warmth and coziness to make it a comfortable living space. When it comes to cold basements, you can blame the floor. The porosity of a concrete floor can make it cold and damp—unwanted characteristics that can be felt through tile, carpet and hardwoods. Simply put, cold basements—even if they’ve been finished—often don’t get as much use as the other more comfortable areas of the house. That’s a lot of space going to waste.

Today, floating subfloor systems offer homeowners a way to stifle the cold and construct a warm, pleasant place for a game room, office area or home theatre. These systems offer a two-pronged approach to keeping concrete floors dry and warm.

First, the plywood or oriented strand board (OSB) subfloor floats on a channeled or “cleated” waterproof underlayment, so the wood never actually touches the floor. The underlayment material can be made of Styrofoam or heavy-duty polyethylene, the same material used in corrugated plastic drain pipe (one of the toughest plastics available). This underlayment creates an air gap above the concrete. Combined with the wooden panels, the air in this space provides a thermal break that acts as insulation to keep floors and rooms warm. These systems can warm a room as much as 10 degrees.

Second, that same layer of insulation provides a moisture barrier against the dampness that naturally rises through concrete slabs. Thanks to the channels in the underlayment, any moisture that does collect can easily drain and evaporate. This protects furnishings and inhibits musty smells and mold growth, ensuring a healthy living space.


Basement Benefits

Floating subfloors are also durable and versatile. The engineered wood core won’t warp, split or peel. The systems are also strong enough to support the heaviest furnishings, such as exercise equipment, pool tables and pianos. And as far as finished floor surfaces, use any flooring solution you want. Simply prepare your new floor as you would any other. These systems allow the option of choosing from carpet, laminate and engineered hardwood. Vinyl tile can be installed in conjunction with a 1/4-inch plywood underlayment. And ceramic tile can be used with a cement board underlayment to provide the utmost strength and sturdiness. (See the manufacturer’s instructions for floor-installation guidelines and warranty specifics.)

These floating systems are also touted as being “ergonomic.” This term refers to the slight “give” in the panels as people step on them. The panels slightly cushion footfalls as the channeled insulation distributes the weight, providing a comfortable, resilient walking surface. Walk on bare concrete and compare it to walking on a floating sublfoor—you’ll see the difference.

With some insulated subfloor systems, thin plastic shims help to level the subfloor on an uneven slab.

With some insulated subfloor systems, thin plastic shims help to level the subfloor on an uneven slab.

Another big benefit for DIY’ers is the ease of installation. While some systems come as rolls of plastic underlayment, most systems are available as 2-by-2-foot interlocking tongue-and-groove panels that have the insulated underside pre-attached to the wood. Just measure the floor and plan your layout in the same manner as laying tile, then tap the panels together with a hammer and wood block. No fastening or gluing is required.

Recently, we installed a floating subfloor system at my friend Robby McConnell’s house. Robby and I have been buddies for years, and he recently had a new daughter. With the expanding family, he felt it was time to expand his living quarters to his unfinished basement. I told Robby about the floating subfloors, and he chose the DRICore brand to install in his basement. Here’s how the project went down.

Snap some chalk lines to help guide the layout.

Snap some chalk lines to help guide the layout.