Summary: Early Insights from Field Observations (March 6, 2025)
The Palisades and Eaton Fires collectively scorched approximately 60 square miles, resulting in the tragic loss of at least 29 lives and the destruction of over 16,000 structures.
- From Wildfire to Conflagration: Strong Santa Ana winds fueled an extreme fire weather setup and, once an ignition occurred, led to rapid, wind-driven, building-to-building fire spread through densely populated communities. The same weather conditions that fuel rapid fire spread grounded the air resources equipped to battle the blazes.
- Structure Density: Under such strong winds, flames from burning buildings bent down and stretched along the wind. For tightly spaced structures, this allowed flames to directly reach from one building to the next. Each home ignition generated high flux of short-range embers and ground-traveling embers, further amplifying the fire. In downtown Altadena and Pacific Palisades, the exposure was so extreme that even homes with some fire-resistant features had little chance of survival because the fire exploited the unmitigated weakest links.
- Connective Fuels & Building Materials: Where structure separation distances were closer to 20 feet, or when exposure was not directly downwind of the fire, fire-resistant building materials played a crucial role in reducing damage severity. These instances interrupted the chain of conflagration, leaving islands of undamaged homes within the scorched community. These homes typically did not have any connective fuels to their surrounding destroyed neighborhoods.
Exposure & Resilience: Among the three pillars of conflagration—structure density, connective fuel, and building materials—structure density and connective fuels couple with environmental conditions to determine thermal exposure intensity. Meanwhile, building materials determine a structure’s resilience to this exposure. When exposure intensity surpasses resilience, structures are not expected to survive. With tight structure density, significant connective fuel, and Santa Ana winds, the exposure level becomes so intense that nearly all building materials are overwhelmed.
- In existing communities where structure separation cannot be changed, removing connective fuels becomes the meaningful lever to reduce exposure levels. Where connective fuels have been addressed, resilient building materials have a better chance of reducing damage.
- Noncombustible fences, such as brick and concrete masonry, can effectively minimize radiation and intermittent flame contact from burning neighbors and compartmentalize fire.
Work towards Wildfire Prepared Home: Typical construction in these communities featured some resilient elements compliant with the Wildfire Prepared Home requirements—such as stucco cladding, Class A roofs, doublepaned tempered windows—but lacked the full system of mitigations. While individually these components provide an acceptable degree of fire resistance, the overall resilience of a structure is determined by its weakest component. Until all components are addressed, the property cannot reap the benefits of the individual component’s fire resistance. Because the remaining weak component varied structure to structure from relatively inexpensive features like vents to more costly features like windows, the cost to mitigate homes in this area varies. But the investment required to enhance resilience in these communities is not as substantial as commonly estimated. Strengthening strategic vulnerable components within an already robust system can significantly improve a home’s resistance to fire.
Published by: Insurance Institute for Business & Home Safety
