Can You Use Polystyrene in Concrete Floors?

Construction

• Polystyrene and/or polyisocyanurate foam are good insulating materials because they are poor conductors of heat. An insulating concrete form contains these materials incorporated into the concrete block. The foam acts as a form for concrete but is left in place rather than being removed after the concrete is poured. The foam can also serve as a backing for flooring material or for interior drywall, depending on the application.

Types

• Insulating concrete forms can be divided into three broad categories. Some of them are flat so that the thickness of the concrete and the foam is pretty much the same in all places. Others create a waffle pattern with foam in certain locations so that the wall is thicker in some places than in others. Finally, post-and-beam systems contain horizontal or vertical concrete columns surrounded by foam.

Techniques

• Builders start by arranging the foam in the desired pattern and shape and connecting the foam boards to each other with plastic ties. Often they'll add steel rods for reinforcement; when the concrete is poured it will congeal around these rods. Designs featuring foam blocks may have steel rods inside the blocks for extra strength. Next the builder pumps concrete into the form, being careful to select the correct rate; pumping concrete too quickly can potentially cause misalignment and form failure.

Considerations

• Insulating concrete forms work for concrete floors. Depending on the design, the foam can potentially provide a conduit for insects or groundwater, so some manufacturers waterproof their foam forms and/or treat them with insecticides. Insulating concrete forms may be more expensive than some of the alternatives but come with benefits like noise reduction and reduced heat loss. Whether they are your best option depends on your budget, design and priorities.