Structures:

Structure Triage

We expect a lot from professional firefighters-justifiably so. Aside from fighting fires we expect firefighters to deal with hazardous materials, be emergency medical technicians and rescue treed cats. Some people expect them to be kamikazes as well-to rush in to defend every house no matter how exposed or ill-prepared it may have been. That is too much. Competence and bravery--yes, suicidal foolishness--no. If you expect a firefighter to risk injury or worse defending your house, you have to give him something to work with, and it wouldn't hurt to give him the incentive of a defensible space to work in.

Research on the subject shows that a few factors have a great influence on the survivability of a structure. These four are the main ones:
o ease of access to the property by firefighters
o roof construction
o defensible space
o the slope of the land

Firefighters are trained to evaluate the survival chances of structures threatened with fire. At a higher level, fire commanders have to consider how much risk it is wise for their crews to accept. Safety aside, firefighting resources are not easily replaced.

The following is from a paper prepared by a student at the National Fire Academy's Strategic Analysis of Fire Department Operations course (National Fire Academy, 1990):

"'Triage' originates from a word meaning to divide into three parts. Basically, it amounts to: 1) eliminate the hopeless; 2) ignore the unnecessary; 3) deal with the rest. While we, as firefighters, hesitate to write off any threatened structure, triage is necessary to prevent futile waste of effort. Trying to save more than you realistically can might very well result in the loss of everything, including homes you could have saved. Forget the structures that are impossible or too dangerous to defend; leave those that are too well involved to save. Ignore, for now, the structures needing little or no protection. Concentrate on seriously threatened but savable structures." (Brown, Structure Triage During Wildland/Urban Interface/Intermix Fires, 1994)

We who remember the '93 fire may by spoiled by the immense resources that were available in that case. The resources assembled for that fire were the largest ever assembled in the U.S.

The checklists provided below highlight the same factors firefighters will be using. You can make your own judgment about how much defensible space you can or want to provide, and your own guess about the firefighter's triage judgment.

On the following pages [in the print edition] you'll find two methods of evaluating the wildfire vulnerability of your home. They were developed by the Utah and Virginia State Departments of Forestry to provide property owners and professionals a quick but reasonable tool for the purpose.

The Utah rating scale [Figure 8 in the print edition of this study], requires a little explanation. "Slope Rating" is the slope of the land surrounding the building in degrees. "Aspect" is the direction in which the land slopes (level being no slope.) "Weather" is the number of days per year on which the local Fire Department declares critical weather. In our Santa Monica Mountains, 20-30 Red Flag days are declared per year. I don't know what the Utah criteria are for critical weather, but they probably are not far different from our Red Flag criteria which are: winds over 25 m.p.h.; humidity of 15% or less, and a burning index of 81 or more. "FD Resp" is the time in minutes of the local fire station.

The vulnerability total for any building is derived by reading down each column to the relevant line and picking up the number of points. The total points given by this system may be a little low because of the slow response time the Utah model expects, probably due to the low density of the rural population. In Los Angeles County, even before the fire "season" has begun in August or September, a brush fire call will be bring a response from multiple stations and helicopters, typically in under ten minutes.

The Virginia Vulnerability Assessment form [Figure 9 in the print edition of this study], is reasonably self-explanatory. Filling in the blanks and adding up the points will give you a rough idea of the fire vulnerability of your home. A point total of 0-19 points suggests low vulnerability; 20-39 points suggests medium risk; and 40-60 points suggests something needs to be done.

Applying both systems to your home will give you a reason to look at your place with open eyes, which can only be a good thing.

The most critical single factor regarding the physical siting of your home is the slope of the ground. Heat rises and fire follows it. Fire usually will move much faster uphill than down.

The next factor is the interaction between wind and the ground. High wind will blow embers far ahead of the flame-front itself. This can cause the apparent speed and direction of the fire's spread to change erratically-another reason to be sure someone is watching for fire in a full circle all around you.

Often the fire will jump from one side of a valley to another without actually burning right down to the bottom and up the other side. This may be due to the effects of micro-climates. The valley bottom may be shaded much of the day and thus remain cooler. The fire is very sensitive to temperature differences and to relative humidity.

If, however the wind is blowing along the length of the valley or canyon or arroyo, it may blow in enough hot air to evaporate any moisture. Moreover, if the canyon is narrow and steep it may begin to act as a chimney, actually drawing air in and accelerating it uphill. This can preheat the vegetation in the canyon enough to drive combustible oils and gasses out of the vegetation. Under these conditions the fire might flash up the canyon at very great speed-almost explosively.

These rather technical considerations can have vital implications for you. First, if your home is at the top of a slope or in the middle of a slope you need to pay close attention to the downslope side of your place. Second, you need to do what you can to remove or cover up features of your home that may trap heat flowing uphill toward your house.

To take full advantage of the view, houses are often sited right on the edge of the crest or projecting out over the ground. The deck may be constructed to give unobstructed views. The undersides of such houses and decks can trap air that may become hot enough to ignite before actual flames reach the house. Boxing in these areas with non-combustible materials would be wise. Similarly, closing the openings to carports or sheds will prevent hot air being trapped inside structures which could be ignited thereby.

Outside of the house you also want to look for places where wind currents cause leaves and other litter to pile up. These are often inside corners formed by the main house and an L-shaped projection. These are areas to which the fire winds will tend to carry embers. Pergolas, arbors and sun shades can also cause the same problems. Hedges and trellis-borne flowers are also vulnerable to the drying and combustion of flowing hot air. Stand away, downhill from your place and look up at it to get a perspective on these potential hot air traps.

If you cannot or will not eliminate these traps by boxing or cutting away the vegetation, then your fire plan must include action to be taken in the event of a fire. Otherwise you are inviting direct impingement of flame on your house-a very difficult situation with which to deal, and not an attractive feature for firefighters assessing their options for defending the neighborhood.

The most vulnerable part of the house, or any structure, is the roof, because many embers being blown ahead of the fire are going to land on it. Unless the roof is in good repair and made of fire resistant material, the chance of serious damage or loss of your house is ten times what it would otherwise be.

Class A asphalt shingles will resist a substantial firebrand burning through to the wooden underside of the roof for a couple of hours--more than enough if someone is there to see--but they will burn through eventually. Better to use fireproof roofing materials if you have a choice.

The real improvement to survivability a fireproof roof can give is illustrated by the following graph. Based on studies of past major fires, it compares the likelihood that a given structure would survive, depending on whether the roof were of untreated wood shake or fire resistant. The fire resistant roofed structure is three times more likely to survive if flames can be kept at least 30 feet away.

State of repair is important, because gaps in coverage of places where the roofing may be torn or lifted up might allow embers to be blown in where the fire resistance may be degraded.

The eaves are especially vulnerable for either of two reasons. First, conventional roof construction leaves some space between the underside of the roof and the ceiling below. This space must be vented to allow air to circulate through to prevent moisture buildup, otherwise the excess moisture can lead to rotting in the roof structure. The winds in a wildfire can blow hard enough to blow burning embers through the vents into this space where fire could break out, unseen, hours after the flame-front has moved on. This is actually a common cause of the loss of houses.
The best preventive is to put metal screen over the vents to keep embers out. The screen should be 1/8-inch mesh. Vents needing to be screened may be found in several places, not only under the eaves. Other vents are located at the roof ends. Vents are also found near laundry dryers and utility areas, especially where gas-fired water heaters are installed. Vents may be found wherever spaces are closed to free-air circulation. Search them out and screen them.

Unusually deep eaves may also trap heat, preheating parts of the house and risking becoming hot enough to ignite. The problem is especially bad at the inside corners of "L's" around the house. Sun shades, arbors, awnings, etc., can cause the same problems.

Leaf and small branch litter can build up on flat or low-angled roofs. Even if the roof surface itself is fire resistant, if there is enough litter to support a fire, that heat alone could ignite the underlying structure. Gutters pose a similar problem if they are allowed to accumulate litter. Fire in the gutter could cause nearby structures to ignite directly or by the build-up of sufficient heat.

A prime source of this kind of litter is overhanging branches. The dangers of the litter apart, there is also the possibility that substantial branches falling onto the roof could break a skylight or damage the fire resistant roofing enough to expose the interior of the structure to embers and super-heated air. Branches too near the structure could also be blown against it hard enough to break windows or otherwise expose the interior to the fire.

Radiant heat from the flames may become hot enough to ignite combustible materials before the flames themselves impinge on your house. That is why exposed wood is given fire resistive ratings based on thickness. A 6"x6" post will take longer to burn through and collapse than a 4"x4". If your house has wooden siding or exposed wooden structural members, this section is for you.

Air is a good insulator, thus the universal urging in the literature for owners to maintain at least a 30-foot ring of clear space around their homes. If the wind is not too high, or the surrounding brush not too dense, this cleared space alone could go a long way toward protecting your home--always expecting that the roof will be a Class A fire resistant one.

Most material dealing with this cleared or defensible space advocates banning plantings or trees. That may be too categorical. The key is to ensure that whatever is in that space cannot support flames long enough to impinge on the structure directly or, viewed another way, that the burning of anything in that space will not generate enough heat to ignite the structure.

Isolated trees, or hedges and plantings kept well trimmed, might still fit the bill, but always with the proviso that flames from vegetation inside that space cannot reach the structure itself.

There is good evidence from large fires that structures with a 30-foot cleared space have much higher chances of survival even without any help from owners or firefighters. Figure 10 [in the print edition] shows that while 40% of dwellings with brush immediately adjacent were destroyed, the percentage fell to less than 5% if brush were kept at least 30 feet away.

Figure 14 [in the print edition] makes rather a worst case because it assumes a fire probably larger than most we would have to deal with-a flame-front some 60' high by 150' long (20x50 meters). The simulations we sponsored suggest flame heights in Topanga might seldom reach such heights or solid widths. We can't say what they will be, although the aim of Dr. Cohen's work is to devise a model that can be applied to individual cases. In the meanwhile, note that the reason the curve representing ignition time rises so steeply is that air--space--is a good heat insulator.

Most new homes in Topanga are being built with stucco walls. This is certainly safer in the event of a fire, but it is not entirely sufficient. Remember that wooden beams supporting decks and roof overhangs are vulnerable, and if ignited could carry fire through the wall into the house itself. Even stucco is no defense against hot flames directly up against the wall so that heat ignites what may be behind the stucco. The flame itself may crack the stucco and penetrate the wall.

For wood siding there are fire retardant treatments that can be pressure-sprayed onto existing wooden structures. Much is claimed for these, but their true effectiveness and how long the treatments remain effective are not known. For structures such as these the solutions are good brush clearing and vegetation control together with active firefighting methods.

These methods involve a pump and independent power supply, hoses and independent water supply. A gas-powered pump and a sufficient water supply would permit a homeowner to defend his home, especially if brush clearing had been well done. Today, technology has improved on plain water. Various configurations of foam and gel additives are available that permit more latitude in the time when such treatments could be applied and greatly improve the firefighting effectiveness of plain water. More details about these systems are given below in the section "If You Stay"

Windows are part of the walls, but they pose their own problems in a wildfire. Most windows are single-pane, standard strength glass. Such windows will not stand much heat before cracking or failing altogether. Similarly, the frames of many windows are wood, aluminum or plastic. These materials, when subjected to high heat, could fail, permitting sparks, embers and hot air to enter the home. Single-pane glass will transmit radiant heat almost as though nothing were there. Radiant heat alone can ignite materials inside the house.

Metal blinds or shutters, or double-paned insulated glass in the windows are alternatives. Commercial and some Topanga home-brew solutions are available, but cost dollars or much time. T-CEP has information on some these if you need it. Essentially, you just want to reduce the flow of heat through the glass into the structure. In an emergency, ordinary aluminum foil taped inside the windows could reflect much of the heat.

Clearly the larger the windows and the less thought given to their vulnerability, the more potential danger there is from them. This is especially significant for homes at the crest of a slope or on mid-slope sites which may have to deal with major heat flows rising to them. The combination-often seen in Topanga-of large wooden decks, large window areas, surrounding trees and deep overhanging eaves, combines heat traps, flammable structures and weak spots where fire could penetrate into the home.

ou can expect every element of your home to pose problems as well as opportunities for fire safety planning. These are only guidelines and suggestions. You will have to cast your own critical eye at your place. If you are starting from the bare earth, or planning a major renovation or addition, the following Firewise checklist is a good place to start. There are ideas here you might use for renovations or mitigation of some existing problems. The Firewise project and web site provide homeowners access to a wealth of information.

(source: Web site www.firewise.org)

When constructing, renovating, or adding to a firewise home, consider the following:
o.Choose a firewise location
o.Design and build a firewise structure
o.Employ firewise landscaping and maintenance. [See Appendix E for a fuel modification diagram.]

To select a firewise location, observe the following:
o. Slope of terrain; be sure to build on the most level portion of the land since fire spreads rapidly, even on minor slopes.
o.Set your single-story structure at least 30 feet back from any ridge or cliff; increase distance if your home will be higher than one story.

o.In designing and building your firewise structure, remember that the primary goals are fuel and exposure reduction. To this end:
o.Use construction materials that are fire-resistant or non-combustible whenever possible.
o. For roof construction, consider using materials such as Class A asphalt shingles, slate oracle tile, metal, cement and concrete products, or terra cotta tiles.
o. Constructing a fire resistant sub-roof can add protection as well.
o.On exterior wall cladding, fire resistive materials such as stucco or masonry are much better than vinyl which can soften and melt.
o.Consider both size and materials for windows; smaller panes hold up better in their frames than larger ones; double-pane glass and tempered glass are more effective than single-pane glass; plastic skylights can melt.
o.Cover windows and skylights with non-flammable screening shutters.
o.To prevent sparks from entering your home through vents, cover exterior attic and under-floor vents with wire mesh no larger than 1/8-inch; make sure under-eave and soffit vents are closer to the roof line than the wall; and box-in eaves, but provide adequate ventilation to prevent condensation.
o.Include a driveway that is wide enough--12 feet wide with a vertical clearance of 15 feet and a slope that is less than 12%--to provide easy access for fire engines. The driveway and access roads should be well-maintained, clearly marked, and include ample turnaround space near the house. Also consider access to water supply, if possible.
o.Provide at least two ground-level doors for safety exits and at least two means of escape--either a door or window--in each room, so everyone has a way out.
o.Keep gutters, eaves, and roof clear of leaves and other debris.
o.Make an occasional inspection of your home, looking for deterioration such as breaks and spaces between roof tiles, warping wood, or cracks and crevices in the structure.
o.Also, inspect your property, clearing dead wood and dense vegetation at least 30 feet from your house, and moving firewood away from the house or attachments, like fences or decks.

Any structures attached to the house, such as decks, porches, fences, and outbuildings should be considered part of the house. These structures can act as fuses or fuel bridges, particularly if constructed from flammable materials. Therefore, consider the following:
o.If you wish to attach an all-wood fence to your home, use masonry or metal as a protective barrier between the fence and house.
o.Use non-flammable metal when constructing a trellis and cover it with high-moisture, non-flammable vegetation.
o.Prevent combustible materials and debris from accumulating beneath patio, deck or elevated porches; screen under or box in areas below ground line with wire mesh no larger than 1/8-inch.
o.Make sure an elevated wooden deck is not located at the top of a hill where it will be in direct line of a fire moving upslope; consider a terrace instead.

Access additional information on the Firewise home page: www.firewise.org.

Neighborhood

The neighborhoods of Topanga are dictated by the terrain and the character of the roads. That means they are of all different shapes and sizes--from compact groups of a few houses to dozens scattered along canyon bottoms.

Steep hills and sharp curves characterize most of the roads, even the main Topanga Canyon Boulevard or Old Topanga Canyon Road. Topanga is not easy driving at best. Under stress, with many vehicles trying to move quickly in both directions, and with poor visibility on top of the steepness and narrowness common to most roads, accidents are all but inevitable. Some of our neighborhoods could become dangerous traps.

Some neighborhoods have only one exit road, and a narrow one at that. There are two things you want from a neighborhood--more than one means of escape and help from your neighbors in an emergency. The more restricted your exit, the more important it is that you look to making it safe to stay. If that's not possible, then you have to accept the implication--to leave early.

Even in the very worst case, however, all parts of Topanga are unlikely to be threatened by the same fire. In nearly all likely cases the majority of Topanga will not be threatened and the best thing for most people to do will be to remain calm and at home, plugged into the T-CEP communication net via their own radios or a communications contact in their neighborhood. We have much more to say about communications later. By all means listen to one of the news radio or TV stations. Undoubtedly the TV stations will be giving wall-to-wall coverage of the fire. However experience suggests much of what they say will be, if not wrong, then not entirely accurate.

A saddle is the low area between two high points or hilltops in a ridge line. In a wildfire saddles become channels for high winds as the heat from the fire flows uphill. The wind tends to speed up as it squeezes between the hilltops and then blows over the ridge with greater force. Saddles are not good places to site homes, nor are they good places to seek refuge if caught in the open by a wildfire.

A chimney is a narrow side canyon usually tilted up toward a ridge line. The steeper and narrower the side canyon, the more it will act like a chimney drawing hot air from a fire into it and speeding it uphill. Chimneys can become infernos in a wildfire.

Chimney and saddles are especially important for their effects on roads running across a slope. Heat normally flows uphill anyway, but a road passing through a chimney can represent a major danger to a vehicle trying to use the road, whether a fire engine or someone seeking to escape the fire. The same is true for vehicles following a road passing through a saddle. Fire conditions can worsen almost in an instant.

Chimneys can be recognized by the fact that when a road turns into the hillside it may be passing into a chimney. When the road seems to pointing away from the hillside it is leaving a chimney and heading toward the 'nose.' The nose, or most forward part of the curve, is probably the safest place to be if caught in the open. This is because the wind and heat tend to flow to either side of the nose. If caught in this position, lie in as bare a spot as you can find on the uphill side of the road in as low a spot as you can-in a ditch if possible. This maximizes the chance that the wind will carry the heat of the fire over you.

Heat is a major risk factor and potential killer. Dehydration is the least of it, though is not to be ignored. In the wind-driven fire typical of wildfires in our area, the hot wind can cause serious burns if bare skin is left exposed too long. Wind gusts can carry bursts of super-heated air that can cause serious burns almost instantly. Strong winds can drive a literal blizzard of sparks, burning branches, hot dust and sand, all of which lodge in clothing or even wrinkles in skin.

The psychological effects of the stress of remaining near a wildfire in full cry may cause one to become less sensitive to pain. The result can be that you may not become aware of a burn until after it has become potentially serious. The following diagram suggests the extent of the danger. The suggested margins are not forbidden zones, rather they suggest the precautions one needs to take and the danger one needs to be aware of within 200-400 feet of a wildfire.

Have we mentioned communications? Being able to access reliable information is at the core of any emergency preparedness scheme. Only then can you know when it might be wiser to evacuate or feasible to stay.

This is not an easy problem to solve. In times past, the public media have been notoriously inaccurate. In the 1993 fire, locations named as aflame were not and sometimes were said to be miles from their true locations. This not a criticism of the media--they do what they can with what they have--but it is a cautionary note, and a prime reason why T-CEP exists.

T-CEP tries to deal with this issue in two main ways--via the Hotline and the Disaster Response Team HAM radio network. The Hotline number is 310/455-3000. It is shared between the Topanga Town Council and T-CEP. In normal times it connects to an answering machine. In the event of some local problem, such as a temporary road closure, there will be announcements on the machine, but normally there will be no one to answer the phone. In a major emergency, however, the T-CEP Hotline Team staffs four incoming phone lines in our Emergency Operations Center (EOC) to receive information from residents and to answer questions with the most recent reliable information available to us.

Topanga boasts two main radio networks--the T-CEP Disaster Response Team (DRT) net which is used to gather and coordinate information among all T-CEP elements, and the Arson Watch. They are technically different, but they connect to the EOC where radio operators are able to communicate throughout the Canyon. DRT and Arson Watch radio operators cooperate in an emergency to make sure both nets are open. Depending on the situation, Arson Watch and DRT mobile teams may be out and about the area checking for damage, helping control traffic and verifying information reported to the EOC by other means.

In this way T-CEP is able to quickly establish a sense of what the situation is and to relay this information to official agencies as well as concerned residents who will be calling the Hotline.

At the same time, information gathered and verified at the EOC is relayed to the relevant emergency authorities, whether the Sheriff, California Highway Patrol, Fire Department, Caltrans, County Public Works or whoever may be in a position to respond with help. T-CEP has spent much time and effort establishing and maintaining these links to the larger world of disaster responders. Residents need to incorporate in their emergency plans how they will connect with T-CEP information. The Hotline number, again, is 310/455-3000. In the '96 wildfire and the El Niño storms of '97 and '98 the EOC was active, and handled as many as 700 phone calls in an 18-hour period.

One way you can keep informed and help T-CEP keep up-to-date is by volunteering to become a local correspondent, taking some training with the DRT so you know how it works, and acquiring a radio capable of communicating with the T-CEP Emergency Operations Center. In this way you can act as your neighborhood's eyes and ears with T-CEP.

Your decision to remain in the case of a wildfire should be predicated on a commitment to obtain the necessary information to make your place as fire safe as possible. You should also recognize that by staying you are volunteering to become a firefighter--you will certainly be running the risks of a firefighter.

It behooves you, therefore, to get at least some basic training. Firefighting is a technical subject, but there are books on firefighting technique. The Los Angeles County Fire Department Station 69 in Topanga sponsors a "call firefighter" team of volunteers who undergo formal training as firefighters.

T-CEP has developed a training program for its volunteers. Some of those courses are available at minimum cost to the public. These include Red Cross certified first aid and CPR (for adults and children) as well as a series of Red Cross disaster-related courses such as Damage Assessment and Living With Earthquakes.

Two T-CEP members recently attended a week-long course to become certified instructors for the national Community Emergency Response Team (CERT) program. This course is taught as a series of seven two-to-three-hour-long classes. They are conducted over a crowded weekend or on seven consecutive Thursday evenings, for example. The CERT program deals with all forms of disaster, disaster psychology, elementary first aid and introductory urban search and rescue. It is an excellent overview and highly recommended for personal information or as a basis for volunteering with another organization.

The more of your senses actively involved with information, the better you remember. Silent reading is good. Hearing information while seeing it is better--that's why television commercials work. Acting out, reciting poetry or playing a role is better yet because it involves the whole body in the process of learning. And best of all is to involve the emotions with the information.

This whole-body involvement with information is the basis for the drills that T-CEP conducts several times a year. It's why the Fire and Sheriff Departments spend a substantial proportion of their time and dollars on training. If you must act under the stress of an emergency, you will be much more likely to recall what you should be doing if you have not only written it down and talked about it but have also acted it out.

Even within your own family, conducting rehearsals will give everyone a better grasp of what might happen and how they might be expected to behave. Familiarity will help reduce the stress level in a real event. Rehearsals can be simple affairs such as sitting around a table and playing "what if" games. Keying the discussion to the day's news is a good way into the discussion. If there had been a house fire that day it could raise the issue, "What would we have done if that fire had started a big one?" Or, "They're predicting Santa Anas, what have we been intending to do about the wood pile?"

Kids in school can play a very useful role if they use show-and-tells, book reports or other writing assignments to gather information or talk about subjects related to emergency preparation. There are many ways to stay engaged with the topic. The more frequently you do it, the less strange and frightening it becomes and the more it seems like just good sense-like looking both ways when you cross a street.