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Hurricanes. Tornadoes. Oppressive heat. Bone chilling cold. Sooner or later, every home in the United States will be affected by at least one of these weather conditions. But there's a home construction method that can take almost anything Mother Nature can throw at it — insulating concrete forms or ICFs.

What are ICFs?

ICFs are typically made of expanded polystyrene. An ICF system provides an exoskeleton for creating the reinforced concrete wall. "The way the forms are designed, reinforcement bars can be spaced in a specified arrangement or grid, so the architect can specify the steel to withstand wind loads, projectiles, excessive backfill pressures and multistory," Jim Buttrey of ICF manufacturer IntegraSpec explains. Depending on the ICF form manufacturer, webs or spacers made of plastic are inserted between the forms in the factory or on-site to hold the forms in place. After being set up and reinforced, concrete in a standard wall mix of 3,000 psi with a 5- to 6-in. slump is poured between the forms. The concrete core thickness can be varied as needed based on project requirements.

The forms come with built-in furring strips so the outside of the house can be finished with any desired material, while the inside gets the normal drywall. "They're used for sheetrock, siding, masonry with brick ties, and the furring strips are buried for stucco friendliness," says Buttrey. Another benefit of building with ICFs is that fewer trades are needed to complete the job, as the wall structure, furring, vapor barrier, insulation and air barrier are all done in one step by one crew.

Concrete contractors who already know how to build masonry or poured concrete homes can learn how to build with ICFs in one week. Manufacturers support users in several ways. For example, IntegraSpec provides technical manuals online, as well as offering help from its regional representatives and in-house training department.

Weather protection

The basic North American configuration of a residential ICF wall is a conventional 6-in. wall containing a 1/2-in. steel grid. Buttrey says this wall can withstand wind speeds of up to 150 mph. With thicker walls and more steel, higher wind resistance is achieved. The walls are also highly resistant to flying projectiles. When a 2x4 was shot at an ICF wall at 100 mph, the wall was not penetrated.