In an unprecedented reversal of American history the US population is becoming less concentrated in urban areas. Many Americans are moving out of big cities and metropolitan areas en route to the suburbs, exurbs, and rural areas.
As more and more people live in and around forests, grasslands, shrub lands, and other natural areas—places referred to as wildland-urban interface, or WUI zones—problems related to wildfires are exacerbated. There are more wildfires due to human ignition. Wildfires that do occur pose a greater risk to lives and homes, they are hard to fight, and it becomes impossible to let natural fires burn.1National Academy of Sciences Furthermore, the expenses to reduce fire hazards, battle rapidly spreading fires, and protect homes and human lives have risen pointedly in recent decades.
What is the Wildland Urban Interface (WUI)?
The wildland urban interface consists of geographical areas where human development and infrastructure (e.g., cell towers, schools, water supply facilities, etc.) meet or intermingle with undeveloped wildlands.
They are locations where wildfires have their greatest impacts on people and property. WUI zones are of concern for the public, federal, state, and local governments, so wildfire mitigation and preparedness are necessary when living within WUI zones.
Where is the Wildland Urban Interface Within the US?
Across the United States, wildland-urban interface zones in areas within California, Utah, Arizona and Oregon are experiencing wildfires. California has the most densely packed WUI in the United States.2Rethinking the Wildland-Urban Interface. Currently, they have just over 11.2 million people living in about 4.46 million homes across 6.7 million acres. Six of the twenty largest wildfires in California history were part of the 2020 wildfire season. Five of the new wildfires ranking in the top 10 were all a part of the August 2020 lightning fires. 3California Department of Forestry and Fire Protection (CAL FIRE)
In the Pacific northwest and the lake states, forests are the predominant wildland fuel. In southern California, chaparral brush predominates. The plains states have grass and oak woodlands, New Jersey has Pine Barrens, and the southeast has pine and hardwood forests.4FEMA
Given that wildfires can occur in any wildland area; and the number of acres burned has been increasing; and the number of houses in the WUI is increasing, federal, state, and local government agencies are focusing more on promoting the concept of “fire-adapted” communities. 5USDA A fire adapted community is defined by the United States Forest Service as “a knowledgeable and engaged community in which the awareness and actions of residents regarding infrastructure, buildings, landscaping, and the surrounding ecosystem lessens the need for extensive protection actions and enables the community to safely accept fire as a part of the surrounding landscape.” 6The Fire Adapted Communities Learning Network
Introduction of Wildland Urban Interface Construction Codes
As of January 2008, the 2007 California Building Code (CBC) went into effect along with the inclusion of Wildland Urban Interface building standards. For building products to be used in the (WUI) or State Responsibility Area (SRA), regulations require that building products comply with specific directives. In terms of fire resistance and ignition resistance the primary goal of the WUI code is to hold construction practices to higher standards in the built environment. When a home or structure is designed and built with attention to detail and careful consideration of complaint building materials, it increases the chances of a structure’s survival in a wildfire.
California Fire Standards for WUI Compliant Exterior Wood Products
According to California Building Code (CBC), the minimum requirement for building envelope components such as siding/cladding is that an exterior wall covering or wall assembly shall comply with one of the following requirements:
- Noncombustible material
- Ignition-resistant material
- Heavy timber exterior wall assembly
- Log wall construction assembly
- Wall assemblies that have been tested in accordance with the test procedures for a 10-minute direct flame contact exposure test set forth in ASTM E2707 with the conditions of acceptance shown in Section 707A.3.1
- Wall assemblies that meet the performance criteria in accordance with the test procedures for a 10-minute direct flame contact exposure test set forth in SFM Standard 12-7A-1.
The benefits of using real wood cladding with wall assemblies that meet the performance criteria set forth in SFM Standard 12-7A-1 are tremendous:
- When compared to noncombustible building materials such as steel and masonry, using WUI compliant exterior wood cladding and wall assemblies offer a sustainable, environmentally friendly, carbon neutral solution.
- Ignition resistant fire-retardant-treated wood is impregnated with chemicals, so the use of paints, coating, stains or other visually pleasing surface treatments are not an option.
- From an architectural and design perspective, WUI compliant exterior wood cladding has many aesthetically pleasing options to suite any project, with a bevy of species and finish options to choose from.
- Exterior timber cladding is a versatile, timeless building material that works well in traditional or contemporary architecture.
- Not only is real wood recyclable and biodegradable, but it also has strength, toughness, and durability that rivals many other exterior facade options on the market today.
reSAWN TIMBER co.’s Abodo® Vulcan Cladding was recently tested on an exterior wall assembly in accordance with the California Standards Code, Chapter 12-7A, SFM 12-7A-1 (Siding Materials for Exterior Wall Siding and Sheathing). The test simulated wildfire conditions using full size 4′ x 8′ panels that were exposed to a flame of 150 Kw for ten minutes. After, the panels were then observed for 60 minutes to check for further flaming. In order to gather accurate results, the process was repeated three times.
Wall System: Exterior Wall Assembly
Combustible Components: 5/8 in. thick FlamePro Plywood sheathing, Wrapsheild RS™ Rainscreen 3 mm, Tongue & Groove Abodo Vulcan Exterior Wood Cladding
A SFM Standard 12-7A-1 pass is achieved if:
- There is an absence of flame penetration through the wall assembly.
- There is an absence of glowing combustion on the interior of the assembly after 70 minutes.
- A test for siding in both a horizontal and vertical orientation is required to be sure of performance.
reSAWN TIMBER co.’s Abodo Vulcan Cladding is WUI Compliant
reSAWN TIMBER co.’s Abodo Vulcan cladding passed the test for both horizontal and vertical orientations for upcoming inclusion in the WUI Products Listing. A copy of the test results can be found here. The result? Abodo Vulcan cladding is now a compliant wildland urban interface building material.
| SFM Standard 12-7A-1 Test Requirements | Test Results | Pass/Fail |
| Absence of flame penetration through the wall assembly at any time. | Flame penetration through the assembly was not observed during the full duration of the test | PASS |
| Absence of evidence of glowing combustion on the interior surface of the assembly at the end of the 70-minute test | Evidence of glowing combustion on the interior surface of the assembly at the end of the 70-minute duration for all three tests was not present | PASS |
Abodo Vulcan thermally modified wood cladding is created from New Zealand plantation timber and engineered with a patented vertical grain orientation for superior weathering characteristics. A fine-sawn face provides beautiful grain depth and optimal coating performance.
Builders can rest-assured when choosing a wall assembly that combines reSAWN TIMBER co.’s Vulcan Cladding with fire-rated sheathing or gypsum board, the result is durable, CAL FIRE WUI compliant exterior siding that is impervious to hazardous weather conditions.
Since reSAWN’s Abodo Vulcan Cladding is pre-finished in modern, beautiful tones, architects and designers can confidently specify carbon negative, high performance, visually pleasing Vulcan exterior siding in wildland-urban interface zones. Clients are left with a stunning, natural, one-of-a-kind facade that can be easily maintained throughout the product lifecycle.
If you’d like to learn more about specifying reSAWN’s CalFire compliant Abodo Vulcan Cladding in Wildland Urban Interface zones, get in touch with us.
