Concrete is one of the most resistant substances to intense heat and fire. A finished ICF wall, mudded and taped, provides a solid concrete exterior with a 3-4 hour fire rating. According to the ICFA, concrete structures are more likely to remain standing through fire than structures of other materials. Unlike wood, concrete does not burn. Unlike steel, it does not soften and bend. Concrete does not break down until it is exposed to thousands of degrees Fahrenheit. The house shown above was built with Amvic™ Insulated Concrete Forms and was one of the few fortunate homes to survive the wildfire.
Completed Amvic™ ICF R30 walls offer a sustainable and resilient building structure with R-Value of 30, STC rating of 50+ and a Fire Resistance Rating (FRR) of 3+ hours.
This stands out when compared to wood-frame homes, which lose stability much faster, increasing the risk of injuries and fatalities due to collapsing walls and falling debris. Concerned about the Expanded Polystyrene (EPS) insulation? According to a study by the Southwest Pacific Research Institute, the emissions from burning polystyrene are “no more toxic” than smoke from wood-frame housing.
According to the California State Fire Marshall, most of the existing building code requirements that relate to fire danger have been derived from decades of experience in urban fires. While this experience remains valid, there is a process underway of study of the experiences of recent years from losses in wildfires in the west. Changes in the codes are being evaluated and will be forthcoming in the near future. Current minimum building codes prescribe standards that generally prove to be less than sufficient in a wildfire scenario. There are planned changes that will stiffen requirements in the future, but there are some simple steps that can be considered now in planning new construction in an area where wildfire is a threat. These design issues and practices can make the difference between destruction and survival. And the cost differences are generally minor.
The following are some suggestions to consider when building a fire safe home
Exterior walls
You can build homes with essentially fireproof walls. One method of doing this would be to use Amvic insulated concrete wall system. An Insulated Concrete Form (ICF) wall provides a solid flat wall of concrete sandwiched between two layers of EPS foam. An ICF wall with a 6” core of solid concrete provides a building shell with a wall fire rating of greater than 3 hours.
Learn more: Fire Resistance Rating of Amvic™ ICF
Roofs
The other important detail of fire safe construction is using a fire-resistant roofing material. Class-A fiberglass, cement-tile or metal roof coverings should be used in designated high-hazard areas on all new construction, additions or repairs. Eave-end gaps in tile roofs should be fire-stopped with cement mortar or metal bird stops, which are available at most roofing supply stores.
When used for roofs, AmDeck™ provides protection against fire and extreme weather such as tornadoes and hurricanes. In addition, the EPS used in AmDeck™ provides continuous thermal insulation and considerably reduces the amount of sound transmission between floors.
Learn more: Amdeck: Insulated Concrete Floor and Roof System
Eves & Soffits
Do not leave exposed rafter tails. Enclose eves and rafter tails with a soffit of fireproof material. This can either be a fire resistant fiber-cement board product or stucco.
Decks
Use a fire proof or fire resistant material for decks. The best case is a concrete deck either as an ICF-formed concrete deck such as AmDeck™ or a concrete slab poured over a steel frame. Many modern synthetic materials are more resistant to fire than natural wood products.
- Skirt decks to within 6” of the ground with solid sides such that flying embers or a grass fire can’t get under the deck.
- Wood deck and trellis members should be a minimum 2×4 dimension; wood beams, floor joists and stair stringers a minimum 4×6 dimension; and posts a minimum 6×6 dimension.
- All such wood should be UBC-approved fire-retardant material or cement plastered.
All projections, such as roof overhangs, balconies, decks, exterior stairs, carports or patio covers, should be protected on their undersides and on exposed edges with cement plaster. Or they should be protected with a continuous wall, most likely poured-in-place concrete or cinder block, around the perimeter of the projection from the underside down to the existing grade; or with UBC approved fire-retardant wood specially treated with fire-retardant chemicals.
Propane tanks
Locate at least 30 feet away from the structure.
Defensible space & fire resistant materials
Follow State Fire Marshall guidelines. The same practices that apply to existing structures should be planned in for new construction.
For further information, there are numerous sources on Firesafe construction tips for new construction on the web: https://www.nfpa.org/
Learn more about our ICF here: Amvic™ ICF Blocks
Please note that this article is for educational purposes only – when designing your fire resistant home, please make sure you always consult with an architect or engineer first.