From SIPs to straw bales, there are numerous alternative approaches to traditional wood-frame structure for the outside walls of a home. One is insulated concrete form (ICF) construction.

Whilst not the least costly means of construction, ICF construction makes houses extremely energy efficient in addition to very quiet in the interior. In climates with temperature extremes, such as very humid and warm or very cold — or in regions close to noisy highways and train tracks — ICF structure will most likely pay dividends over the duration of the home.

AIA, Bud Dietrich

An insulated concrete form is a combination of two panels of rigid insulation that normally measure 32 inches by 16 inches by 2 inches. These rigid insulation panels are held 4 or more inches apart by plastic webs. The ICFs are stacked on top of each other in a staggered pattern, forming a pit that concrete will become poured into. The exact product varies among producers.

The vinyl webs in those forms keep the rigid insulation from getting pushed out by the weight of the wet concrete as it has poured, while the rigid insulating material creates the formwork that the concrete will be held within.

ICF manufacturers normally make pieces that create a 90-degree corner, in addition to other specialty forms for angled walls and curved walls. There really isn’t any restriction on the overall layout when you’re using ICFs.

Typical ICF structure has reinforcing bars set in the concrete. While these bars aren’t shown in these sketches, they are an essential component of any ICF wall system.

AIA, Bud Dietrich

An ICF wall can start out thicker in the lower levels, where the wall is encouraging more fat and must also resist the inward pressure of the ground, and then make thinner as it gets taller. While the depth of the rigid insulating material doesn’t change, the thickness of the concrete does. This ensures an efficient utilization of concrete, the major structural component of the wall, while keeping up the wall’s insulating value.

Bud Dietrich, AIA

Changing the wall depth where there will be a floor provides a ledge where the framing for that floor structure can sit. In this way the floor can be traditional, common and inexpensive wood-framed structure, whether using standard dimensional lumber or long span joists.

AIA, Bud Dietrich

Finishing walls constructed with ICFs isn’t much different than for other construction types. Sheets of drywall can be attached right to the types by screwing them into the plastic verticals provided. These plastic verticals, which can be extensions of the plastic webs, are typically set at 8 inches on center to accommodate 4- by 8-foot sheets of drywall, such as.

A contractor usually installs electrical devices in these partitions by directing out a part of their rigid insulation to provide a space for conduit and wiring. Even though this will diminish the insulating value of the wall, the overall wall structure will still be highly effective.

Before Photo

AIA, Bud Dietrich

Last, while using insulated concrete forms is a great way to construct an energy-efficient and quiet residence, you won’t end up with an easily modifiable structure. Since the walls are made of concrete and reinforcing steel, it’s important that you understand well in advance the exact location and dimensions of door and window openings. You simply don’t want to begin adding windows or doors or changing sizes after the walls are erected. Doing your homework upwards is beneficial for any project, but it’s essential once you’re building with ICFs.

More in Know Your Own House:
What Makes Up a House’s Foundation | What constitutes a Floor Structure
Components of Powerful Walls | Components of a Roof

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