BLOCK FIRE RISK
On this page, you’ll learn how the first house on a block ignited by wind-blown embers can turn into a Serrano-wide conflagration—and how homeowners on the block and the HOA can reduce this risk.
A block is a group of homes bordered by streets—and in some cases by open space or golf course fairways as well.
Within those boundaries are deed-owned parcels, privacy wood fences, and HOA-maintained front yards, streetscapes, and slopes.
The HOA and Country Club maintain vegetation buffers in the open space and along fairways within 100 feet of structures, reducing the potential for spot fires started by wind-blown embers, creating a fire path toward homes.
Definitions
A block fire starts when windblown embers ignite the first home on a block, and the flames, radiant heat, and embers from that house fire ignite the next downwind home—continuing from house to house until the fire reaches the end of the block.
Block Fire
Streets may stop the spread of flames and radiant heat, but embers from burning homes can travel beyond the block and ignite houses in the next block. This process can repeat from block to block—turning a wildfire into a community-wide conflagration.
Based on post-wildfire damage assessments and fire science research, structure separation distance is the most important driver of house-to-house fires.
In fires such as the 2021 Marshall Fire in Boulder, Colorado, neighborhoods with homes separated by only 10–20 feet experienced rapid, wind-driven house-to-house ignition. In Serrano, the separation distance in most villages is typically in that range.
Serrano Strategy
Marshall Fire
Boulder County, Colorado
December 2021
Serrano Village
Once a home ignites, there is more than a 90 percent chance it will become a total loss without fire department intervention.
More importantly, the flames, radiant heat, and embers produced by a burning home can ignite the nearest downwind house, regardless of its building materials or nearby vegetation.
What this means for Serrano is simple: prevent the first house on every block from igniting. To do that, homeowners on every block should:
Ensure all homeowners take concrete steps to greatly reduce their home’s vulnerability to wind‑driven embers.
Work with the HOA to identify and reduce all fuels on the block that could allow flames to spread from combustible materials to nearby homes.
Request a Block Assessment to get started.
The following block-level fuels can contribute to the spread of fire toward homes and across a block. Each is discussed in more detail below:
Wood privacy fencing that connects to homes on the block
Wood fencing along open space
Streetscape fencing and landscaping
Slope landscaping
Open space and fairway vegetation within 100 feet of structures
Wood Privacy Fencing
A wood fence fire anywhere on the block can act as a wick—carrying flames directly to homes and spreading fire across the block.
In many cases, embers do not ignite the fence boards directly. Instead, embers strike the fence and fall to the ground, landing in bark mulch, dry leaves, and yard debris along the base. These materials ignite easily and set the fence on fire.
Once ignited, a fence fire can reach your home through the wood gate and the attached “wing fence” section connected to the structure.
Along the side yard, windblown flames and radiant heat can threaten:
Nearby windows
Exposed eaves above
Bark mulch along the foundation
Shrubs and vegetation near the gate
Combustible items stored against the fence
Replacing an entire wood fence with metal can be very expensive—often around $10,000 per side.
Another option is to replace the wood gate and the first five feet of attached fence with HOA-approved metal. This breaks a fire pathway to and from your home. Typical cost: $2,200–$2,700, depending on post size and installation.
However, this option does not eliminate the risk of a fence fire traveling along the side of two homes. A burning fence can ignite vegetation and combustible materials on both sides, threatening windows and eaves—and potentially leading to one or more home ignitions.
Metal Gate
Metal Attached Fence
Wood Fencing Along Open Space
Two villages—D1 and B—have wood fences that border the open space instead of the metal fencing used elsewhere in Serrano. Many of these homes are located within five feet of the open space boundary.
Replacing wood fencing along the Village D1 and B open space with noncombustible fencing would significantly reduce ignition and fire-spread risk for these homes and the blocks where they are located.
Streetscape vegetation and bark mulch next to wood fences can pose a serious hazard to every home on the block. Streetscape vegetation, bark mulch, and wood fences can act as connective fuels, carrying fire directly to the front of the house and igniting combustible materials in the side yard along the way, projecting radiant heat and direct flames onto vulnerable windows and eaves. A house next to a street scape that is ignited can set off a chain reaction, spreading fire from house to house to the other end of the block.
Block risk will be lower if the HOA takes the following action:
Remove bark mulch and yard debris along wood fence lines
Keep vegetation at least 5 feet away from wood fences next to streets
Break up fuel continuity wherever wood fences border landscaped areas
Streetscape Fencing and Landscaping
Slope Landscaping
Open Space Clearance
Fairway Clearance
Sources
2024 Serrano Wildland Urban Interface Fire Safe Plan. Serrano El Dorado Owners Association. December 2024.
Giammanco, I., et al. The Return of Conflagration in Our Built Environment. IBHS. September 2023
Hedayati, F., et al. Wind-Driven Building-to-Building Fire Spread: Experimental Results and Probabilistic Modeling. Fire Technology. January 2026.
IBHS Research. Post-Event Investigation: California Wildfires of 2017 and 2018. July 2020.
IBHS Standard. Wildfire Prepared Neighborhood Technical Standard. Version 2025.
Maranghides, A., et al. NIST Outdoor Structure Separation Experiments (NOSSE) with Wind. NIST Technical Note 2253. May 2023.
Maranghides, A., et al. WUI Structure/Parcel/Community Fire Hazard Mitigation Methodology. NIST Techncal Note 2205. March 2022.
Monroy, X., et al. The 2025 LA Conflagrations. IBHS. December 2025.
Zamanialaei, M., et al. Fire Risk to Structures in California's Wildland-Urban Interface. Native Communications. August 2025
