Insulating concrete form

Insulating concrete forms or insulated concrete forms (ICF) are a building system to create reinforced concrete walls or floors with integral insulation. They are dry-stacked (without mortar) and filled with concrete. The units interlock somewhat like Lego bricks and create the formwork for reinforced concrete that becomes the structural walls, floors or roofs of a building. The forms stay in place after the concrete is cured and provide a permanent interior and exterior substrate for finishes. The forms come in different shapes, sizes and are made from different materials depending on the manufacturer. ICF construction has become commonplace for both low rise commercial and high performance residential construction as more stringent energy efficiency and natural disaster resistant building codes are adopted.

The first expanded polystyrene ICF Wall forms were developed in the late 1960s with the expiration of the original patent and the advent of modern foam plastics by BASF. ^{[citation needed]} Canadian contractor Werner Gregori filed the first patent for a foam concrete form in 1966 with a block "measuring 16 inches high by 48 inches long with a tongue-and-groove interlock, metal ties, and a waffle-grid core." It is right to point out that a primordial form of ICF formwork dates back to 1907, as evidenced by the patent entitled “building-block”, inventor L. R. Franklin. This patent claimed a parallelepiped-shaped brick having a central cylindrical cavity, connected to the upper and lower faces by countersink.

The adoption of ICF construction has steadily increased since the 1970s, though it was initially hampered by lack of awareness, building codes, and confusion caused by many different manufacturers selling slightly different ICF designs rather than focusing on industry standardization. ICF construction is now part of most building codes and accepted in most jurisdictions in the developed world.

Reinforcing steel bars (rebar) are usually placed inside the forms before concrete is poured to give the concrete flexural strength, similar to bridges and high-rise buildings made of reinforced concrete. Like other concrete formwork, the forms are filled with concrete in 1-foot to 4-foot high "lifts" to manage the concrete pressure and reduce the risk of blowouts.

After the concrete has cured, the forms are left in place permanently to provide a variety of benefits, depending on materials used:

Insulating concrete forms are commonly categorized in three manners. Organizations whose first concern relates to the concrete structure classify them first by the shape of the concrete inside the form. Organizations whose first concern relates to the material or fabrication of the forms classify them first by the characteristics of the forms themselves.

For Flat Wall System ICFs, the concrete has the shape of a flat wall of solid reinforced concrete, similar to the shape of a concrete wall constructed using removable forms.

For Screen Grid System ICFs, the concrete has the shape of the metal in a screen, with horizontal and vertical channels of reinforced concrete separated by areas of solid form material.