Rammed Earth & Wildfire

Building Complexities in the Wildland Urban Interface

Overview

Authors

Photo of Brittany Dhawan, AIA

Brittany Dhawan, AIA

Architect / Owner

Studio 144 Architects

brittany@studio144architects.com


Keywords


Abstract

California is set to be drier and more drought prone with climate change. Wildfire and the subsequent loss of life and housing is a huge challenge. Current WUI (Wildland Urban Interface) building codes address some reduction in flammability, but with the current buildup of the forests due to decades of complete fire suppression techniques, wildfires have been uncontrollable. Wood framed housing is the most prevalent building type for single family homes and is extremely vulnerable in the event of a wildfire. Rammed earth construction, which is far less flammable has been overlooked as a potential construction type for single family housing. Rammed earth walls have not been tested for a fire rating in the US or Canada, or a test to determine non-combustibility. Currently the building codes are being rewritten, including the codes for the WUI zone. The insurance industry in California is also reeling from the wildfires and has discontinued coverage for sometimes whole counties in fire zones. If the disconnected interests of the homeowners, home builders, insurance industry, and regulatory officials were to seriously look at rammed earth for replacement housing in communities destroyed by wildfire – the small fees required for testing this wall type wouldn’t seem insurmountable anymore.

Introduction

Wildfires are becoming more destructive and the wildfire season is lengthening from climate change. In this map from Cal Fire dated 2007, before several of our worst fire seasons, much

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Background

One reason why rammed earth construction was perhaps not appealing in the US building industry is that there isn’t sufficient testing that would have convinced many to use this method

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Case Study #1

Mr. Bernie Krause had a rammed earth home built in Glen Ellen, California. His house was burned in the Northern California wildfires that hit hard the Napa / Sonoma area

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Case Study #2

Bruce & Leslie Steidl had a rammed earth house that was also destroyed in the Napa / Sonoma area wildfires of 2017. Their house had a standing seam metal roof

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Sustainability

The soil mix for rammed earth walls can be as low as 0.023 kgCO2 / kg in embodied carbon content for rammed earth mixes with site soil and no chemical

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Conclusion and Future Work

Laurel Hunter lost her house in the Camp fire in Paradise, California. Now noted as the “worst fire in California history.” She was lucky to get out with her family

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Acknowledgements

Heather Heppner, Laurel Hunter, Duke Crestfield, P.E., Triangle Engineering, Peter Slack (writer of Firewise Construction) & his daughter, Jocelyn Lawrence-Barish, Joss Krayenhoff, Sirewall USA, Jeanette Torres, Underwriters Laboratory, Bernie Krause, Dan Alvarado (Rammed Earth Works), Anirudh Dhawan.

Rights and Permissions

[1] "California Fire Hazard Severity Zone Map." California Fire Hazard Zone Severity Map. 2007. Accessed June 25, 2019. http://www.fire.ca.gov/fire_prevention/fire_prevention_wildland_statewide. (Public Domain)

[2]United States. State of California. Department of Insurance. The Availability and Affordability of Coverage for Wildfire Loss in Residential Property Insurance in the Wildland-Urban Interface and Other High-Risk Areas of California: CDI Summary and Proposed Solutions. By Tony Cignarale, Joel Laucher, Kenneth Allen, and Lisbeth Landsman-Smith. 2018. Accessed June 29, 2019. http://www.insurance.ca.gov/0400-news/0100-press-releases/2018/upload/nr002-2018AvailabilityandAffordabilityofWildfireCoverage.pdf.

[3] Bartolone, Pauline. “Their Home Survived The Camp Fire - But Their Insurance Did Not.” NPR, NPR,

17 Feb. 2019, [4]"Camp" class="redactor-autoparser-object">www.npr.org/2019/02/17/6952059... Fire Incident Information." Incident Information. November 8, 2018. Accessed June 26, 2019. [5]"California" class="redactor-autoparser-object">http://cdfdata.fire.ca.gov/inc... Statewide Fire Summary". CAL FIRE. State of California. Retrieved October 30, 2017

[6] "Glendale Childcare Center." Marmol Radziner Architecture. Accessed April 20, 2019. [7] Sirewall" class="redactor-autoparser-object">http://www.marmol-radziner.com... System, https://sirewall.com/sirewall-...

[8]Krahn, Tim, and Meror Krayenhoff. Essential Rammed Earth Construction: The Complete Step-by-step Guide. Gabriola Island (B.C.): New Society Publishers., 2019.

[9] Alvarado, Dan. Personal Interview. 30 Sept. 2019.

[10] CSIRO Bulletin 5, section 3.4.1, test on 250 mm thick rammed earth wall

[11] New Zealand NZ 4297 Earth Building Standard, Section 5.5.1

[12] New Zealand Concrete Masonry Manual, Section 2.1

[13] UL 419, Underwriters Laboratory, Public Domain image.

[14] "Mineral Commodity Summaries, Gypsum." National Minerals Information Center. 2018. Accessed June 25, 2019. [15] “New" class="redactor-autoparser-object">https://www.usgs.gov/centers/n... Message from SIREWALL USA.” New Message from SIREWALL USA, 18 May 2019.

[16]Slack, Peter. "Firewise Construction." Community Fire Prevention Partnership Firewise. 2000. Accessed May 06, 2019. https://mountainscholar.org/bitstream/handle/10217/41498/Firewise_Construction_Design_and_Materials.pdf.

[17]Newberry, Laura. "As California Fire Disasters Worsen, Insurers Are Pulling out and Stranding Homeowners." L.A.Times, August 31, 2018. Accessed June 29, 2019. As California fire disasters worsen, insurers are pulling out and stranding homeowners.

[18] “Interactive Map of Fire Destruction throughout Sonoma County.” Accessed October 11, 2019. [19] Cal" class="redactor-autoparser-object">https://www.sonomanews.com/mul... Fire Graphic, public domain.

[20] “Photos of a Rammed Earth House Post Wildfire.” Photos of a Rammed Earth House Post Wildfire, 11 Oct. 2019.