ICFs 101: Fire Resistance

Of all construction materials, concrete is one of the most resistant to heat and fire. That fire resistance gives houses built with ICFs (insulating concrete forms) certain safety advantages. And those advantages give you yet another reason to consider using ICFs for your custom home.


How well do ICF walls hold up in a fire?
Unlike wood, concrete does not burn. Unlike steel, it does not soften and bend. Concrete does not burn until it is exposed to thousands of degrees Fahrenheit — far more than is present in the typical house fire.

This has been confirmed in so-called “fire-wall” tests. In these tests, ICF walls were subjected to
continuous gas flames and temperatures of up to 2000°F for as long as four hours. None of the ICF
walls ever failed structurally. All of the ICFs tested were of the “flat” or “uninterrupted grid” type,
having no significant breaks in the concrete layer [like BuildBlock ICFs]. In contrast, wood frame
walls typically collapse in an hour or less.

Do they stop fire from spreading?
Concrete walls have also proven more resistant to allowing fire to pass from one side of the wall
to the other. This is especially of interest in areas with brush fires that could spread indoors.
The fire wall test confirms this rule for ICFs once again. Part of the test measured how well the
wall slows the passage of heat and fire from the side with the flame to the other side. The ICF walls
tested did not allow flames to pass directly through. They also did not allow enough heat through to
start a fire on the cool side for 2-4 hours. In contrast, wood frame walls typically allow both flame and
fire-starting heat through in an hour of less.

Will the foam add fuel to the fire?
The foams in ICFs are manufactured with flame-retardant additives. These prevent the foams from burning by themselves. If you hold a match to the material, it will melt away. Of course, in a house fire the foam may be subjected to constant flame from other materials burning nearby (wooden floors, fabrics, etc.).

The “Steiner Tunnel Test” measure how much a material carries fire from an outside source. In the test, technicians line a tunnel with the material, run a fire at one end, then measure how far the flame spreads. The flames travel about one-fifth as far down a tunnel lined with ICF foams as they spread down a tunnel lined with wood.

Can the foam give off harmful emissions?
Practically any organic material, be it wood or plastic, gives off emissions when it is subjected to intense heat or flame. The Southwest Research Institute reviewed the numerous existing studies of fire emissions and concluded that the emissions from polystyrene foams are “no more toxic” than those of wood.

For more information about building your new custom home with ICFs, contact Custom Homes LTD for a builder consultation. (210) 559-9293