What are the Best Tips for Basement Floor Insulation?

The best tips for basement floor insulation are to use materials that will both trap warm air in the extended living space while keeping moisture out. These materials are generally most effective when installed prior to laying the concrete foundation for the home. When insulating the basement floor of an existing home, one can use similar components to create a new floor on top of the current concrete slab.

Basements are living areas beneath the main floor of a home. They are typically located below ground level and are dug prior to home construction by the builder. They are most commonly made from concrete that is poured directly against the dirt foundation. These areas tend to remain several degrees cooler than the rest of the home due to their underground location; concrete naturally absorbs small amounts of water over time and can easily become cold, reflecting the ground temperature around it.

Temperature differences between basements and the main floors of a building can occur in any part of the world regardless of the type of climate in which the home is located. The damp, cool air that circulates in below-ground spaces can create excellent conditions for mold growth. Proper basement floor insulation not only increases the amount of comfortable living space in the home, but also can protect its occupants from unwanted structural damage and health hazards.

It is generally a good idea to install basement floor insulation before pouring the concrete foundation slab. This provides a moisture barrier between the damp earth and the naturally absorbent concrete of the home. This can be accomplished by pouring a 1- to 2-inch (2.5 cm to 5.1 cm) deep layer of gravel roughly 1 inch (2.5 cm) below the recommended grade level — the depth at which the basement is dug — for the basement floor. The gravel can then be covered with different types of insulating materials and poured with concrete. The gravel allows water to drain beneath the home without collecting in standing pools around the foundation.

The best types of material to use for basement floor insulation are foam boards designed for use as insulation and polyethylene, a type of plastic sheeting that can be used as a vapor barrier. Both are commonly available at home improvement stores and through the Internet. These may be laid over a gravel foundation before concrete is poured or over a pre-existing concrete slab. Foam helps trap warm air in the living space, while the polyethylene prevents moisture from entering the air from the surrounding earth.

When using these methods over an already poured concrete slab, sheets of pressure-treated plywood may be placed over the layers of basement floor insulation to create a sub floor. Carpet or hardwood can be installed directly over the plywood to finish the living area. New flooring should not be installed directly over the concrete, as it will continue to absorb moisture from the earth and transmit it to the new carpet pad or wood. The foundation of the home should also be properly drained before attempting to create a new floor over an existing space. Standing water that collects around the home can seep through the concrete floor and walls and easily damage carpet and hardwood.