ICF are basically forms for poured concrete walls, that stay in place as a permanent part of the wall assembly.
The forms, made of foam insulation, are either pre-formed interlocking blocks or separate panels connected with plastic ties. The left-in-place forms not only provide a continuous insulation and sound barrier, but also a backing for drywall on the inside, and stucco, lap siding, or brick on the outside.
Although all ICFs are identical in principle, the various brands differ widely in the details of their shapes, cavities and component parts.
Block systems have the smallest individual units, ranging from 8" x 1'4" (height X length) to 1'4" x 4'. A typical ICF block is 10" in overall width, with a 6" cavity for the concrete. The units are factory-molded with special interlocking edges that allow them to fit together much like plastic children's blocks.
Panel systems have the largest units, ranging from roughly 1' x 8' to 4' x 12'.. Their foam edges are flat, and interconnection requires attachment of a separate connector or "tie." Panels are assembled into units before setting in place - either on-site or by the local distributor prior to delivery.
Plank systems are similar to panel systems, but generally use smaller faces of foam, ranging in height from 8" to 12"and in width from 4' to 8' . The major difference between planks and panels is assembly.. The foam planks are outfitted with ties as part of the setting sequence, rather than being pre-assembled into units.
Within these broad categories of ICFs, individual brands vary in their cavity design. "Flat wall" systems yield a continuous thickness of concrete, like a conventional poured wall. "Waffle grid wall" systems have a waffle pattern where the concrete is thicker at some points than others. "Screen grid" systems have equally spaced horizontal and vertical columns of concrete which are completely encapsulated in foam. Whatever the differences among ICF brands, all major ICF systems are engineer-designed, code-accepted, and field-proven.