Rebuilding the Wildland-Urban Interface: Why a Fire-Resistant House Alone Isn't Enough
After the 2025 Los Angeles wildfires destroyed more than 16,000 structures in the Palisades and Altadena, architects, engineers, and urban planners flooded the rebuilding conversation with exactly the kinds of proposals you'd expect. Better materials. Fire-resistant cladding. Upgraded vent protection. Noncombustible construction. All of it technically correct and most of it insufficient on its own.
The problem that kept surfacing among architects working on the ground in the recovery was blunter than the policy debate acknowledged: a fire-resistant house placed back into an unchanged neighborhood doesn't behave like a fire-resistant house during a wildfire. It behaves like a slightly better target in an environment that hasn't changed. The embers that jump from a burning wood house 60 feet upwind don't know that your new home was built with fiber cement siding and ember-resistant vents. The fire that's moving through a neighborhood carries with it the collective fuel load of everything around it.
This is the argument for thinking about WUI architecture at the neighborhood scale, not just the lot scale. It's an argument that LA architects Greg Kochanowski, Barbara Bestor, and Zoltan Pali have all made in different ways since the fires. And it's an argument that has real architectural and engineering implications for how we think about rebuilding and how we think about new development in fire-prone regions.
1. The Individual House Problem
Most WUI building codes and most WUI architectural guidance is written around the individual structure. Title 24, Part 7, California's new consolidated WUI code, specifies requirements for exterior wall assemblies, roofing, vents, glazing, and decks. Those requirements are real and meaningful. A home built to full WUI compliance is genuinely more survivable than one that isn't.
But those requirements are written as if the structure exists in isolation, assessed against a fire exposure condition defined by its own defensible space zone and its own ember exposure. The code doesn't account for what happens when the house next door hasn't been rebuilt yet and is still the original 1970s wood-frame construction. It doesn't account for the gap in a block where a non-rebuilt lot becomes an unmanaged accumulation of fire-prone vegetation. And it doesn't account for the fact that even a perfectly built WUI-compliant home can be ignited by embers that travel half a mile from a burning neighbor two streets away.
That's not an argument against building to WUI code. It's an argument that building to WUI code is necessary but not sufficient for community-level resilience.
What LA Architects Said After the Fires
Architect Greg Kochanowski, whose firm was involved in post-fire recovery design, put it directly: 'Unfortunately, we have seen mostly isolated building proposals rather than systemic and holistic strategic thinking up to this point. A resilient house that is disconnected from infrastructure planning, code pathways, and insurance recognition risks remaining symbolic rather than systemic.' That gap between individual compliance and systemic resilience is the central architectural design challenge of WUI rebuilding.
2. Defensible Space at the Block Level
Defensible space is the concept most people have heard applied to the individual property: clear vegetation within a certain distance of the house, create a buffer zone that slows fire approach. California law requires 100 feet of defensible space for most homes in designated fire hazard zones, in two zones: Zone 1 (0 to 30 feet) with the most aggressive vegetation management and Zone 2 (30 to 100 feet) with spacing and clearance requirements designed to slow fire spread.
Applied only at the individual lot level, defensible space has a fundamental limitation: it creates isolated islands of managed vegetation in what may be an otherwise continuous fuel load. When those islands are densely packed in a neighborhood, the 30-foot Zone 1 clearance from one house may be immediately adjacent to the unmanaged vegetation of the neighboring lot. The fire doesn't distinguish.
Block-level defensible space planning changes the geometry. Instead of thinking about each lot's clearance zone independently, you think about the block as a system. Where are the gaps in vegetation management? Which lots have fuel accumulations that create ignition risk for their neighbors? Where are the pathways that fire uses to cross from one block to another? This kind of analysis is fundamentally architectural and planning work, done at a scale that individual lot design doesn't address.
Ember corridors and neighborhood layout
Wind-driven embers are the primary ignition mechanism in most large wildfire events, including the 2025 LA fires. Embers travel on wind currents, sometimes for half a mile or more, landing on combustible surfaces wherever wind patterns carry them. Neighborhood layout matters because certain configurations concentrate ember deposition. Cul-de-sacs with inward-facing houses create a bowl geometry that traps embers. Streets oriented parallel to the prevailing fire weather wind direction create ember corridors. Densely canopied street trees can carry fire across a block even when individual structures are compliant.
Understanding ember deposition patterns at the neighborhood scale is increasingly a tool that architects and planners are applying to WUI communities. BIM-based fire simulation tools can model ember travel paths based on terrain, vegetation, and building layout, giving design teams a picture of where defensible space management matters most and where building siting decisions have the highest protective value. That level of analysis isn't required by code for most projects, but it's increasingly available and increasingly being used by practitioners committed to something beyond code minimum.
3. Setbacks, Streets, and the Public Realm
One of the most underused tools in WUI neighborhood design is setback geometry. The distance between a structure and its property line, the distance between structures across a street, and the width and materials of the street itself all affect how fire behaves in a neighborhood.
Wider setbacks create more physical separation between structures, reducing the radiant heat and ember exposure that a burning building creates for its neighbor. In a densely built neighborhood where lots are 5,000 square feet or less, setback distances may be relatively small, creating tight neighbor-to-neighbor spacing that increases mutual exposure. In those neighborhoods, material choices are doing most of the fire resilience work. In less dense settings where setbacks can be increased, the physical separation is a meaningful layer of protection that doesn't depend on material specifications.
Street width also matters. A wider street provides more separation between structures on opposite sides and can slow fire spread across the street. Permeable paving materials and drought-tolerant street tree species that don't create continuous canopy cover contribute to a street environment that's less hospitable to fire spread. These are landscape and planning decisions more than architectural ones, but they're decisions that architects designing in WUI neighborhoods need to understand and advocate for.
4. The Insurance Dimension
One of the practical drivers pushing toward community-scale WUI resilience is the collapse of the private homeowner insurance market in California's fire-prone zones. Multiple major carriers have exited the state or dramatically restricted coverage. The California FAIR Plan, the state's insurer of last resort, has seen its exposure grow enormously as private carriers withdrew.
The insurance problem is partly a building-by-building risk assessment problem, and some of the reforms underway address it that way: insurance modeling that credits WUI-compliant construction, inspection programs that document compliance, and mitigation credits for defensible space maintenance. But it's also fundamentally a neighborhood-level risk problem. An individual home in a WUI-compliant neighborhood where most of the surrounding structures are also WUI-compliant and where vegetation management is consistent has a meaningfully different risk profile than the same home in a neighborhood where it's the only compliant structure.
Community Wildfire Protection Plans, which are formal planning documents developed under the National Cohesive Wildland Fire Management Strategy, are one mechanism for capturing community-scale risk reduction and potentially translating it into insurance market recognition. For developers and community planners, understanding the CWPP process and working within it during project planning is increasingly relevant to the financing and insurability of new development in WUI zones.
5. What Architects Can Do That Engineers Cannot
The argument for architectural leadership in WUI community resilience isn't just about technical compliance. Architecture shapes the experience of a neighborhood and the behavior of the people in it. A neighborhood designed with generous setbacks, fire-resistant street trees, clear sightlines, and consistent defensible space creates a visual language that residents understand as intentional. A neighborhood where those things vary lot by lot and block by block communicates something different, even if every individual structure is technically compliant.
Architects working on post-wildfire rebuilding have an opportunity that doesn't come up often: the chance to design something from scratch, with current knowledge, in a context where the previous design clearly failed. The architects who are using that opportunity to think at the neighborhood scale rather than the lot scale are doing the most interesting and consequential work coming out of the 2025 fires.
For Developers and Homeowners
If you're rebuilding in a post-fire neighborhood or developing in a WUI zone, the most valuable thing you can do is understand the fire history and the neighborhood context before you design the individual structure. Where have fires approached this neighborhood from in the past? What's the prevailing fire weather wind direction? How is the surrounding fuel load managed? What's the ember deposition risk given the terrain and layout? These are questions that a WUI-experienced architect or fire safety consultant can help answer, and the answers shape design decisions that matter more than any single material specification.
Conclusion
The 2025 LA fires produced exactly the kind of architectural reckoning that major disasters sometimes do: a moment where the accumulated shortcomings of individual-lot-scale thinking became undeniable at scale. 16,000 structures don't fail because each one was individually deficient. They fail because the environment they existed in was collectively vulnerable.
The architectural and planning tools to do better exist. Community-scale defensible space planning, ember corridor analysis, setback geometry, street design, and vegetation management at the block level are all available now. What they require is the will to apply them at a scale beyond the individual project, and clients, developers, and communities willing to invest in that kind of thinking.
