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Insulated Concrete Forms

Insulated concrete forms (ICF) come in three main types – Blocks, Planks, and Panels.

Hollow blocks are the most common, with 2 inch thick sides that are held together with plastic or steel connectors that extend to the faces of the block, providing a fastening point for wall finishes. Hollow blocks are normally 16 inches high by 48 inches long.

The overall width of a hollow block depends on the thickness of the concrete, which could vary from 4 to 12 inches or more depending on whether it’s an above grade wall or basement wall.

Plank forms and blocks are similar in comparison, with the only difference being that the foam sides are longer and narrower, most being 1 foot by 8 foot in design.

The third types of Insulated Concrete Forms Panel forms, are normally 4 foot by 8 foot.

The three form types of ICF shape the concrete in one of three ways:

  • flat wall
  • grid wall or
  • post and beam

Flat concrete walls are the easiest of the three to shape. With integral foam insulation being an exception, these walls are similar to traditionally formed concrete walls. If you were to strip away the foam on a grid of ICF, you would see that the form resembles giant waffles.

With a grid wall, the thinnest spots of concrete may only be 2 inches thick, with the thickest usually being six – eight inches. The concrete in a grid can be hung up in thinner areas, which makes them more apt to voids. When you compare grid and flat walls, you will notice that grid Insulated Concrete Form uses less concrete than the flat walls.

Post and beam is the third Insulated Concrete Form. By one of more beams that are supported by posts, the concrete in these walls are formed. Foam used by these forms, is all that fills the space between the concrete. These systems may not be wise to use for below grade use where they must resist a considerable amount of backfill pressure.

You may have also noticed many Insulated Concrete Forms are made from cement composites. These units themselves are actually heavier than foam forms. Despite their being heavier, they still offer many advantages. Many people have concerns with below grade foam and the fact that termites and carpenter ants can easily plow their way through and get into the house.

There are some building codes that actually require below grade foam to be treated in order to resist these pests. If your detail is good, you shouldn’t have to worry about this problem. Composite ICF on the other hand, is one way you can be sure that you won’t have to worry about pests.