Construction Techniques – Insulated Concrete Forms (“ICF”)

By Michael Repka

Over the past decade, the building industry has become more environmentally conscious while also striving to find ways to improve the quality and durability of homes. One construction technique that has seen increased popularity in recent years is building with Insulated Concrete Forms, also known as ICF construction.

Traditional residential construction generally consists of a foundation and framing, comprised of either wood or aluminum studs. In modern construction, the space between the studs on exterior walls is usually filled with insulation of some sort, however there are often insulation gaps near the studs, electrical outlets, and plumbing. While certainly adequate, this technique results in a structure that may lack the structural rigidity and overall insulation of ICF homes.

A Closer Look at ICF Construction

The concept behind ICF construction can be traced back to the three little pigs. When the big bad wolf huffed and puffed, he was able to blow down the two little pigs’ homes that were made of straw and sticks. Yet, the third little pig’s home, which was constructed of bricks, survived the ordeal unscathed. That wolf would not stand a chance against a modern home made with insulated forms reinforced with rebar and filled with concrete.

ICF construction is actually fairly easy to understand. A manufacturer produces forms that are made of insulated panels, which are separated by braces or similar structural dividers. These forms have teeth on the edges such that they can lock together much like Lego® bricks. Once the bricks are in place, reinforcing rebar is added and the gap between the two panels is filled with 8 to 12 inches of concrete. This results in thick, solid walls covered on both the inside and the outside by the insulated panels. Once fully hardened, this process creates walls that are extremely strong, solid and resistant to any sort of air penetration. Plus, even the most ambitious termite would starve to death or move on to one of the delicious wood houses in the neighborhood.

A contractor trained in this building technique will position the “bricks” to form openings for windows and doors before the cement is added. Similarly, all necessary conduits and other internal wall elements are installed prior to filling the walls.

The walls are finished in relatively short sections, roughly four-feet high and filled. If the contractor were to fill a section much higher than four feet, then the weight of the wet cement could cause the forms to bow or fail. While completing walls in four-foot high sections results in a very strong-finished home, the need to have a cement truck make multiple visits to the property can result in significant additional cost.

This building technique is fairly flexible. Builders can use ICF for basements and then switch to more traditional techniques for the living areas, or they can use ICF all the way from the below-grade basement up to the roofline. Generally, once a contractor and/or luxury home builder becomes familiar with this technique, they seem inclined to use it all the way to the roof. On the inside, however, interior walls may be built using traditional methods, ICF, or a combination of both.

Resistance to the Elements

The terrible disasters this nation has faced over the past year, including the hurricanes in Florida, Texas, and Puerto Rico; the wild fires in northern and southern California; and the tornados in the Midwest, may lead to increased interest in ICF construction. After all, homes constructed out of solid concrete walls are much more resistant to wind damage. Additionally, if coupled with a fire resistant roof, this type of construction is likely to fare better in a wild fire when compared with homes constructed out of wood.

Shad Shokralla, of Brighton Builders Limited of Los Altos, a builder experienced in this type of construction, is a strong advocate of this construction method even though it is more costly than traditional methods because the finished product is so solid.

Shad built a masterpiece of ICF construction for a couple in Los Altos Hills, which can be seen at 26401 Eshner Court. These satisfied homeowners love the final product, noting that the entire house feels rock-solid and completely squeak-free.