Combustible vegetation and trees like that surrounding this older San Diego dwelling were a major factor in property losses. A minimum defensible space of 20 to 100 feet surrounding subdivisions permitted fire service personnel to save more recently constructed homes.


The 275,000-acre Cedar Fire that burned into San Diego suburbs was fueled in large part by dead and dying trees.



Strong, erratic winds in San Bernardino drove wildfire through the Del Rosa neighborhood, destroying some homes and sparing others


Old wood shake roofs were responsible for the loss of many homes in the Scripps Ranch community north of San Diego. In January 2004, the San Diego City Council banned the use of wood shingle and wood shake roofs.

socal_UnsafeHistory has a way of repeating itself. In 1993, I traveled to Southern California to investigate the aftermath of the wildfires that occurred in October of that year. This was followed by my publication of an article on the subject in the January-February 1994 edition of Building Standards magazine. Almost exactly ten years later to the day, wildland fires again swept across Southern California from Ventura County to the Mexican border. What sets the recent fires apart was their size and the amount of destruction they caused, burning more than twice the area (approximately 745,800 versus 333,700 acres) and destroying well over three times as many dwellings (approximately 3,340 versus 971 dwellings) as compared to the 1993 fires. By the time the fires were subdued by wet, cool weather, 23 people had been killed and 174 injured. State officials estimate that damages from the fires will exceed $2 billion: the largest property loss from wildfires in the state’s history.

Contributing Factors

socal_MapMany factors contributed to the tremendous loss of life and property—some new, but most recurring. In late October or early November of most years, for example, hot winds blow off of the upper deserts and through the dry Southern California mountain ranges. In addition, forests in the region had experienced a multi-year drought, followed by a bark beetle infestation that killed huge stands of trees. The drought also created enormous amounts of fuel in the form of kiln-dried chaparral shrubs on lands near the Pacific Ocean, especially in San Diego County. Given these conditions, a spark was all that was needed to ignite a conflagration that the hot, dry winds could spread uncontrollably.

There is no question that population growth and development in urban-wildland interface areas have also increased the risk of catastrophic fires.

“There is almost a direct correlation between growth and the number of ignitions,” said University of California, Berkeley, professor Tim Duane, whose statistical survey of California’s Sierra Nevada mountain range indicates that a doubling of population may be responsible for a 5,000 percent increase in property damage.

Also, some housing has been built in so-called “indefensible locations” such as Palmer Canyon in the foothills of the San Bernardino National Forest, where 47 houses once stood but only four remain. Other examples of indefensible locations include the narrow, miles-long canyon containing the Hook Canyon community where 350 homes burned and Crestline, a neighboring community that contained dozens of closely spaced wooden houses surrounded by dry, brittle pine trees which overhung roofs and porches.

The San Bernardino Mountains had not experienced a severe burn in nearly 100 years, in part due to the United States Forest Service’s policy of suppressing fires, leaving the forests with an unprecedented buildup of fuel.  In fact, two months before the fires, Texas A&M University forest ecologist Thomas Bonnicksen warned Congress, “never have I seen anything more dangerous than the overgrown, beetle-ravaged forest. […] I am concerned for the safety of people living in communities surrounded by these forests.” Local politics also contributed to the problem. In the community of Lake Arrowhead, for example, a homeowners association had a longstanding policy of banning property owners from cutting trees in order to help preserve the area’s natural beauty. The ban was lifted a year ago and some residents did what they could to remove the dead pines, but the buildup of dead trees was too dense.

Mitigation Features

Despite the high losses experienced in the 2003 Southern California wildfires, the results could have been much worse if not for changes made in the wake of the 1993 fires. While many homes were lost, the adoption of local ordinances requiring special protection against wildland fires was critical to the preservation of tens of thousands of other dwellings along the several hundred miles of fire perimeter. Local adoption was helped along in part when state lawmakers passed the Bates Bill following the devastating Oakland Hills fire in October 1991. That legislation required the State Fire Marshal to designate high-hazard fire-risk zones and permitted local governments to require stricter building standards within these zones.
socal_UniqueRoof The unique roof eaves and soffits of this undamaged Ventura County home are consistent with the most stringent fire protection requirements of the International Urban-Wildland Interface Code.

Local jurisdictions throughout California have set different standards for building in high-hazard fire-risk zones. While few have specifically adopted comprehensive mitigation provisions such as those provided by the International Urban-Wildland Interface Code™ (IUWIC™), most of the homes recently built in areas of high risk have at least some special features common to that code.

The building features that appeared to have provided the most protection in the recent wildfires were noncombustible (or Class A) roofs and noncombustible exterior wall surfaces, primarily stucco. Other mitigation strategies such as protecting roof eaves, decks and unenclosed underfloor areas with noncombustible materials are also more common now than prior to 1991.

Another feature that was critical to protecting dwellings from the firestorms was the more prevalent use of defensible spaces around individual dwellings or subdivisions. Defensible space is defined in the IUWIC as “an area either natural or man-made where materials capable of allowing a fire to spread unchecked has been treated, cleared or modified to slow the rate and intensity of an advancing wildfire and to create an area for fire suppression.” Because of the combustible nature of many of the materials used, most dwellings constructed in California will burn if directly exposed to 60 mile-per-hour winds and extreme heat unless fire fighters are both quick to react and lucky. It is common practice for fire fighters to triage houses in neighborhoods exposed to fast-moving wildfires. If a dwelling cannot be protected within fifteen minutes, a defense is staged at another one that has a better chance of being saved. As a result, dwellings with the combination of a wood roof and minimal defensive space will get little aid from fire fighters unless there are no other dwellings demanding their attention.

No better example of the significance of defensible space can be found than in Ventura County, which was spared widespread destruction even though more than 172,000 acres were burned in the Simi/Val Verde and Piru fires. Only 37 homes were lost in the county, out of a total of 3,339 destroyed throughout Southern California during the October 2003 wildfires. It is important to note that Ventura County’s brush clearance laws are tougher than most, requiring homeowners to provide a 100-foot clearance around woodland homes each spring rather than the state’s minimum 30 feet of clearance. Ventura’s weed-abatement ordinance is backed by an aggressive enforcement program that includes sending approximately 14,000 warning notices to property owners each year. If a property remains in violation after a second warning, the county contracts for brush clearance and places an assessment on the owner’s property taxes to recoup the costs. The program has been very effective, with the number of homeowners cited for violations dropping each year from a high of nearly 1,000 in 1991 to just 47 in 2002. During this same period, yearly assessments dropped from over $1 million in 1991, to less than $100,000.

Clearly, another critical factor in the preservation of life and property was the courageous efforts of the many fire fighters who responded to the emergency. Even with the expertise that comes from past experience, defending against fires in urban-wildland interface areas is dangerous and grueling work. Mutual aid among neighboring fire departments as well as among regions and states is essential when major disasters like the 2003 firestorms strike, and the effective mobilization of over 14,000 fire fighters and support personnel from throughout the region at the height of the blazes cannot be underestimated.

JUWIC Fire Protection Features

Table 2


There are those who will argue that the October 2003 Southern California wildfires were in many ways a disaster foretold: that it was a tragic but predictable consequence of people wanting to live in forests and brushlands designed by Mother Nature to burn periodically. During a visit to the three hardest hit areas in Ventura, San Bernardino and San Diego Counties immediately after the fires’ containment I found that, contrary to this dire outlook, the vast majority of newer dwellings in the vicinity of the fires’ boundaries were still standing. This bears witness to the fact that building and fire safety officials in the affected areas should be proud of their efforts to educate the public and elected officials about the high priority of adopting and enforcing stringent building and associated wildfire mitigation regulations.

Without the promulgation of standardized provisions like those in the IUWIC, it would be very difficult to achieve the broad application of safe and sound practices to protect people and buildings within our forests and urban-wildland interface areas. Appreciation is therefore also extended to our national codes and standards writing bodies and the dedicated people who serve on their committees. Thank you for a job well done, and keep up the good work!

Click here to read about how One Home Survived California Wildfires.


  1. Laura Parker, Tom Kenworthy and Patrick McMahon. “Areas ‘Disaster Waiting to Happen.’” USA Today Nov. 3, 2003: 4A.
  2. ibid.


Recognition is given to the following individuals who contributed photographs and information for preparation of this article: Paul Bambauer, executive director, Concrete Masonry Association of California and Nevada, Sacramento, California; Chris Hastings, marketing manager, RCP Block & Brick Inc., Lemon Grove, California;  Elizabeth L. Lile, cartographer, United States Geological Survey, Denver, Colorado; Craig Morgan, fire hazard reduction program manager, Ventura County, California, and Drew Probst, website designer/developer, U. S. Geological Survey, Lakewood, Colorado.