Rebuilding With Fire Safe Construction

To view the figures and tables associated with this article, please refer to the flipbook above.

The recent disaster in Pacific Palisades, Malibu, and Altadena areas of Los Angeles County, California has brought the issues of fire damage to the forefront of a national conversation. The Los Angeles fire disaster is estimated to exceed $50 billion in damages, most of this will be underinsured or not insured. Recently, the Grand Canyon North Rim Lodge burned to the ground from the Dragon Bravo Fire. These recent events again bring up the topic of rebuilding homes with “fire-safe” materials to avoid such future catastrophes.

As a country, the United States has the highest proportion of wood-framed buildings in the world. In 2020, residential wood-frame construction accounted for 64% of the fire deaths in 2020. Approximately 70-80% of residential buildings are wood-framed buildings. The five types of construction recognized by the building code are:

Combustible wood-framed buildings are classified as Type V construction structures which have zero-fire resistance. Commercial buildings, retail structures, churches, schools, police stations, fire stations, and government offices are not Type V construction buildings but are Type I construction buildings with maximum fire protection and that also can resist earthquakes, wind forces, and storm effects with greater resiliency.

Then why are homes built out of wood-frame construction?

Wood-frame construction has been the primary building type in the U.S. for over 200 years. The main reason for this is cost and availability of materials. Wood-frame construction is termed, “Light-Frame Construction” by the building code because it is easy to work with. Wood can be cut and placed by carpenters with simple tooling. No heavy machinery is required, and changes can be handled during the construction phase.

The downsides of wood-framed buildings are:

The risk factors for wood-framed buildings include:

Given this track record and known risk factors, this author proposes a new direction for residential buildings.

The number one building system for protection is Type I construction which is specified for shelter structures and “critical facilities” such as police stations, command centers, government offices, military stations, embassies, hospitals, telecommunications facilities, power stations, etc. Facilities that are “must have” are never built as Type V construction. The code and regulations will not allow this because wood-framed buildings have the highest risk of destruction from fire.
In 2008, the author wrote an article recommending the residential home building industry move away from Type V construction, especially in areas of high fire risk [i.e., California].

This author built two prototype buildings of custom home design (Figs. 1-3) The first one was approximately 6,000 square feet located in Monterey, California, in a private development. The second house was approximately 12,500 square feet located in Bell Canyon, California. Both homes have survived for the past 20 years, with several fire threats in the area.

This is not an original idea. Thomas Edison built the first concrete house in 1908 in New Jersey and patented the concept of building mass housing out of concrete with a single pour (Figs. 4-5).
The use of reinforced masonry and/or precast, prestressed hollow core concrete floor planks (e.g. Spancrete) are the best materials for resisting fire because they are noncombustible, eliminating many of the risk factors associated with Type V construction buildings. The advantages of building with masonry and concrete are:

Cost is a significant concern as there is an increased structural cost in materials and labor using reinforced masonry and precast, prestressed hollow core concrete floor planks. The interior improvements, finishes, and mechanical systems will be the same as a Type V building using interior drywall/finished surfaces because they are not changed.

The author recommends adding a sprinkler system for the rooftop framing system powered by a gas generator that draws water from a backyard pool or water tank. This will provide a primary fire protection system to prevent flame spread from the outside through windows that could enter the structure. The cost of this system would be added to the overall structure cost.

The final cost of Type I construction depends on many factors, but industry estimates indicate this should not exceed 15% of the wood-frame system. Each floor plan and design will dictate a different cost profile, so this is not a guarantee, but an educated estimate. The important advantages are clear, and long-term sustainability will add a lifelong security for the home. Also, insurance risk is far less. Survivability of the Type I construction residential structure will match that of other critical facilities like police and fire stations. This Type I construction residential home will be a fortress, and its life equity will remain protected.

For example, in Palisades the projected replacement cost estimates for residential properties are in the range of $600-$850/square foot. This estimate is for higher-end residential rebuilds and depends on interior improvements. The structure’s cost is approximately 50% of the replacement cost or $300-$425/square foot for a two-story wood-framed building of approximately 4,000 square feet, [foundation not included]. Three major areas where reinforced masonry wall and concrete floor systems will reduce costs are:

Certainly, there are disadvantages. Wall and diaphragm designs must be precisely dimensioned and cut to fit perfectly with tight tolerances. One cannot make adjustments in the field to “move a wall” or cut an opening arbitrarily. But this could be an advantage because it forces the design team and owner to reconcile their designs before construction begins and not allow for inordinate change orders during the construction phase.

Final cost estimates of the masonry and concrete Type I construction are emerging to be approximately 15-20% above the wood-frame Type V construction, with reduced insurance risk and long-term sustainability. This is arguably a negligible increase considering the life safety advantages.

The biggest advantage is the reduced risk for total loss. Given the insurance industry crises in California and fire prone states, for many communities in hillside/high fire risk areas this may not be an option, but the only way to build in the future. ■

About the Author

Dilip Khatri, SE, PE, Ph.D, is a professional structural and civil engineer with 42 years of experience and licensed in 48 United States, four Canadian Provinces, and Australia. He has published over 200 technical papers/symposiums/presentations. (dkhatri2006@gmail.com, Khatri-international.com)