Tecnobosque Wildfire Knowledge Graph · Built Environment
Reference Concept · v1.0Definition → relationship → calculation → evidence context
Structure-to-structure spread is fire propagation in which a burning building or built feature becomes a significant source of heat, flames or firebrands that contributes to ignition of another structure.
What is structure-to-structure spread?
A burning structure can produce large flames, radiant heat and a new population of firebrands. If neighbouring buildings are close or vulnerable, these exposures can create a chain of structural ignitions.
The importance of this pathway grows with density, wind, combustible attachments, building materials and the number of simultaneously burning structures.
Why it matters
This pathway helps explain why dense WUI communities can experience cascading losses and why parcel-level vegetation treatment alone may be insufficient.
After one home ignites, the neighbourhood itself can become fuel. Fire can then propagate between buildings even where wildland vegetation is no longer the only dominant source.
What controls or changes this quantity?
Closer buildings receive stronger heat and flame exposure.
Wind tilts flames and transports structural firebrands toward neighbouring properties.
Combustible exterior components and openings influence ignition susceptibility.
Fences, decks, sheds and other features can create intermediate fire pathways between parcels.
Engineering context
Thermal radiation from a burning building heats neighbouring surfaces.
Large flames or burning attachments can directly impinge on another structure.
Burning structural materials can be lofted and deposited farther away.
Multiple burning structures can amplify exposure and produce neighbourhood-scale propagation.
How to interpret it correctly
- Identify whether a neighbouring structure was burning before the receiving structure ignited.
- Separate radiant, flame-contact and firebrand pathways when evidence permits.
- Treat building separation as one factor, not a universal safe-distance threshold.
- Include fences, sheds and other built fuel in parcel-to-parcel pathway analysis.
Use the calculator as a transparent technical aid and keep its assumptions explicit.Explore Wildfire Retrofit Planning →
Why it matters in wildfire analysis
WUI incidents can evolve into community conflagrations where the built environment contributes materially to fire spread. This transition may occur after initial wildfire exposure has already ignited multiple homes.
Tecnobosque connects this concept to Black Box chronology because sequence—what ignited first and when—is essential for attribution.
Limitations and boundaries
- A simple separation distance does not capture wind, flame geometry, building materials or firebrand exposure.
- Post-fire damage patterns can make ignition sequence difficult to reconstruct.
- Community-scale modelling requires more detail than a property checklist or retrofit-cost calculator.
Structure-to-structure Spread FAQ
What is structure-to-structure spread?
It is fire propagation in which a burning structure contributes materially to ignition of another structure.
How can one burning home ignite another?
Important pathways include radiant heat, direct flame contact and firebrands.
Does defensible space prevent structure-to-structure spread?
It can reduce some pathways but cannot eliminate intense exposure from a nearby burning building.
Why does ignition sequence matter?
Knowing which structures burned first helps distinguish vegetation-driven exposure from cascading building-to-building spread.