The wildfires that swept through California between 2013 and 2018 provided a significant dataset for researchers Alexandra D. Syphard and Jon E. Keeley to analyze factors associated with structure loss in their 2019 article Factors Associated with Structure Loss in the 2013–2018 California Wildfires. As an architect with experience designing in these fire-prone regions, I found their study insightful but ultimately lacking in a holistic analysis. Their findings challenge some common assumptions about fire-resistant design but fail to provide a truly comprehensive approach for policy development.

Key Factors in Structural Survivability

The study evaluated approximately 40,000 structures that either survived, sustained damage or were destroyed. Key factors examined included defensible space, defensive actions, and building characteristics. One of the most striking conclusions was that structural characteristics played a more critical role in survivability than defensible space. However, by analyzing these factors as individual elements rather than in combination, the study may be oversimplifying the complexity of designing for wildfire resilience.

Building Characteristics: An Isolated Approach

The research indicated that specific building elements were crucial in determining whether a structure survived a wildfire with Enclosed eaves providing the most significant risk reduction.  Dual-pane windows and vent screens also played a substantial role in protecting homes from ember penetration.  Surprisingly, roofing and exterior siding materials were not as critical as often assumed.

While these findings offer some useful insights, analyzing these components in isolation limits the study’s practical applications. Fire resilience is not determined by a single feature but rather by a combination of elements working together. For example, a structure with enclosed eaves but poor defensible space or highly combustible surroundings is still at considerable risk. A more useful approach would have been to assess clusters of fire-resistant measures and their collective impact.

Defensible Space: A Misleading Evaluation?

The concept of defensible space is well-established in wildfire mitigation. However, the data suggests that the size of these zones may not be as crucial as once thought. Smaller defensible spaces were found to be just as effective as larger ones, provided they were properly maintained.

One critical flaw in this analysis is that the study did not fully account for the type of vegetation within defensible spaces. Simply measuring an irrigated zone as a “defensible space” does not capture the true efficacy of this method to create fire resilience. This is a significant limitation, not a minor one, as understanding fire-resistant landscaping is essential for WUI fire safety.

Limitations and Further Questions

While the study provides valuable insights, it falls short in its ability to generate definitive policy guidelines:

• What commonalities exist among surviving homes beyond individual fire-resistant elements? Are these homes implementing a combination of best practices?
• Some data points seem questionable. For example, masonry decking was found to be slightly riskier than wood decking. This raises concerns about the methodology used in assessing fire resistance factors.
• The study primarily evaluated building characteristics but did not consider the role of utility companies in fire containment. The continued supply of gas and electricity in active burn areas increases combustibility and the potential for secondary explosions, which create new hotspots and hinder containment efforts. This is a significant oversight that should be factored into future research.

The Need for Retrofitting Older Structures

New homes built in fire-prone areas are subject to stricter fire-resistance standards. However, even the most well-designed fire-resistant home remains vulnerable if surrounded by older, non-updated structures. This underscores the urgent need for retrofitting existing homes to modern fire-resistant standards.

One of the easiest and most impactful policy changes would be to implement grant programs or rebate incentives for homeowners who undertake fire safety upgrades. These could help offset the costs of improvements such as:

• Retrofitting eaves and vents with ember-resistant designs
• Installing dual-pane windows
• Removing or replacing flammable deck materials
• Improving defensible space management

Unlike sweeping regulatory changes, these financial incentives provide a practical, immediate path toward increased fire resilience without placing excessive financial burdens on homeowners. By incentivizing upgrades rather than mandating them outright, policymakers can encourage the widespread adoption of fire-resistant measures in older communities.

Final Thoughts

The study’s conclusion that structural characteristics dictate whether a home ignites is compelling but ultimately incomplete as fire resilience is multifaceted. More pre- and post-fire data collection is needed to refine our understanding and improve fire-safe design in the WUI.

As architects, our responsibility extends beyond designing individual fire-resistant structures; we must advocate for broader policy changes that prioritize fire retrofitting, responsible community planning, and resilient infrastructure. The lessons from the 2013–2018 California wildfires provide a foundation for rethinking how we approach fire safety in the built environment, but without a more comprehensive approach to analysis, research like this will remain too isolated to drive truly effective policy change.

All graphics are from the article “Factors Associated with Structure Loss in the 2013–2018 California Wildfires by Alexandra D. Syphard and Jon E. Keeley.

Find a copy of the article here: Factors Associated with Structure Loss in the 2013–2018 California Wildfires