Protecting Residences From Wildfires

Accessories

Although the most important factors in determining the probability of a structure surviving a large wildland fire are the materials ofwhich a residence is constructed and its location with respect to vegetative fuels, others must also be considered. One of the more important is the number, type, and location of various accessories and their manner of installation. Some of these accessories (e.g., wood fences and outbuildings, fuel tanks) can increase the hazard. Others (e.g., brick fences, portable pumps for swimming pools) can reduce it. The effects of some (e.g., water pumps, patios) depend entirely on their manner of installation.


Swimming Pools

Wherever the water supply is adequate to support them, swimming pools have become prominent accessories to rural and suburban homes in recent years, particularly in southern California where the length of the season of their use makes the investment most worthwhile. These pools can be important for providing fire protection to the home, or they can be of no help whatsoever, depending on how they are installed and equipped. To a lesser degree the same can be said for other bodies of water on the premises (e.g., stock ponds, fish ponds, creeks) (Alger 1971, Governor's Study Comm. 1966, Los Angeles City-County Fire Bd. Inquiry 1971, Oreg. St. Dep. of For. 1978a).

The first and simplest way in which pools can be made a part of the fire protection system is their placement and screening. If located on the windward and/or downhill side of the house and screened from public view by masonry or other nonflammable wall or fence they provide a good deal of the needed separation between the structure and the native vegetation. The wall will protect sliding glass doors from radiated heat and may also provide some deflection of wind, thus assisting in protection from windborne firebrands.

The most important benefit of swimming pools or other bodies or water, however, is as a source of firefighting water, but this aid is quickly negated if there is no way to get the water. Every pool, therefore, needs to be so installed and equipped that the water in it can be obtained and used either by a fire engine or by the occupant, or preferably, by both. For the fire engine to get the water it must be able to get close enough to the pool to draft water with its pump and suction hose. If this is not a possibility the pool will need a bottom drain leading to a standpipe near the street to which the engine can hook up. For the occupant to be able to make emergency use of the water, a pumping system is needed. A gasoline-powered portable pump is best for this purpose because of the danger of electric power outages during conflagrations (Oreg. St. Dep. For. 1978a, Task Force on California's Wildland Fire Probl. 1972, Lowden and Degenkolb 1972, Smaus 1978 b).

Proposed Standards:

  1. Provide unobstructed direct access by a fire engine to within 16 feet of the water surface (a gate that can be opened quickly by firemen would not be considered an obstruction).
  2. If Standard 1 is physically impossible, equip the pool with a bottom drain and piping system of 21A-inch minimum diameter that terminates in a valved standpipe. Locate the standpipe where a fire engine may quickly hook up and draft water from it.
  3. In addition to following either Standard 1 or 2, store a portable gasoline-powered pump, complete with 8 feet of suction hose, 100 feet of fire hose, and a fire nozzle, at a place convenient to the pool or other water source.

Fences

Fences are accessory to almost every home. They vary from barbed wire fences which are no more than barriers to certain domestic livestock through various types of decorative and visual barriers, usually made of wood, to high masonry or concrete barriers. They are equally as varied in their effects on wildland fire. Even two fences of exactly the same type may have different effects, depending on how they are maintained.

Barbed wire fences have little or no effect on a fire unless wooden posts are used or they are allowed to accumulate dry grass or other flammables. Other types of wire fences (e.g., hog wire, chain link) collect windblown paper, leaves, and other flammable trash. Unless they are cleaned regularly, they contribute to the natural fuel loading. Rail fences, whether of the post or zigzag variety, add fuels, especially after they become old and weatherbeaten. Essentially solid wood fences (e.g., board, grape stake) present the same problem as rail fences and in addition act as collectors of windborne flammables. Many documented cases point to these fences as the means of carrying the fire to the structure. Masonry or other nonflammable fences may collect flammables, but rarely to such an extent that their effectiveness as a barrier to a ground fire is serious] y reduced. Although this type of fence cannot guarantee protection from windborne firebrands, it has been known to deflect them so that they land in relatively safe areas rather than on the structure or on some other accessory (e.g., wooden sun deck, patio furniture). All types of fences, including barbed wire, tend to become windrows of dry grass and weeds unless well cleaned and maintained annually (Alger 1971, Los Angeles County Fire Dep. 1970. Smaus 1978 b).

Proposed Standards:

  1. Construct fences to the maximum extent possible of open, single-strand wire or of solid masonry construction.
  2. Keep clean of loose flammable materials any fences constructed of meshed wire or of flammable materials.

Outbuildings

Outbuildings include any and all structures associated with but not directly connected to or part of the main building (e.g., detached garages, barns, pump houses, tool houses, tree houses). They are often more vulnerable to a wildfire than is the residence. Most residences are designed and built by professionals and therefore have some degree of fire protection (although seldom adequate) built in, but outbuildings seldom are. They are usually built by the occupant sometime subsequent to, often years after, the construction of the residence. In addition, because of their lower value and the fact that humans rarely live in them, they are usually not as well cleaned and maintained as the house. They tend to start off as poor fire risks and become steadily worse. Fires have been observed spreading from burning outbuildings to residences by radiation, convection, and flying burning shingles (Los Angeles County Fire Dep. 1970). ,

Proposed Standards:

  1. Require outbuildings to meet the same standards for building spacing, roofing materials, brush clearance, etc., as the structure with which they are associated.
  2. Prohibit the use of outbuildings as depositories of discarded flammable materials.

Patios, Sun Decks, and Balconies

If made of nonflammable materials and properly designed, patios, sun decks, and balconies are not only enjoyable but also can be of considerable fire protection value. By becoming part of the brush clearance and landscaping, they help reduce radiant and convective heat on the house. Judicious orientation with respect to slope, wind, picture windows, etc., can deflect wind and heat away from weak points in the fire defenses of a home. On the other hand, if made of wood or other flammable materials, covered with carpet, congested with wood or fabric furniture, or covered by a canopy or trellis, they may easily become the direct means of transmitting fire to the house (Smaus 1978a, 1978b).

Proposed Standards:

  1. Construct patios, sun decks, and balconies of concrete or other nonflammable material wherever possible; but in no case, use any materials having less than 2-hour fire-resistive rating as specified in the UBC.
  2. Do not carpet any unenclosed portions of these accessories.
  3. If canopies or trellises are employed, provide means for quick enclosure so that windblown flames and heat cannot be trapped beneath them.
  4. If the deck or floor level of a patio or sun deck is above ground level, seal off the underside of the deck or floor by skirting or by a wall to keep fire from burning beneath it.

Water Pumps

Most rural and suburban residences in subdivisions subscribe to community water systems of some type. Many that are not in subdivisions get their water from an irrigation district or private water company. Some of the latter homes must provide pressure and storage for themselves. All other residences must provide their own complete independent water systems including well or spring, pump, and storage facilities. Wherever an occupant has to provide the pump, it must be properly designed and installed and be capable of delivering enough volume for effective firefighting, probably considerably more volume than that needed for domestic use. Most such pumps are electrically powered. Care must be taken that power to the pump is not lost at a critical time, and electric service to the pump should be separate from that to the house. Since power company distribution lines can also burn down, a standby gasoline engine-powered pump should be available. Preconnected hoses should also be available both at the pump and elsewhere about the property for immediate use in case of fire (Oreg. St. Dep. For. 1978a).

Proposed Standards:

  1. Install electric water pumps with independent service drops that do not pass through or onto any building.
  2. Install pumps capable of delivering a minimum of 100 gal/min at 50 lb sq.in. pressure (a desirable standard would be 250 gal/rein at 100 lb sq.in.).
  3. Back up electric pumps with a gasoline-powered pump.
  4. Preconnect to the pump or distribution main one or more hoses reserved for firefighting purposes and long enough to reach to all sides and the roof of each building.

Fuel Tanks

Except for suburban subdivisions and some mobile home parks, most rural and wildland residences are heated either by liquid petroleum gas or by fuel oil. In addition many farms and ranches have their own bulk gasoline tanks. If improperly installed, protected, and separated from other structures and vegetative fuels, the containers for these hydrocarbon fuels become extremely dangerous during a fire. They have been known to rupture seams, break connections, and even explode when overheated. They can burn with intense heat, often in the form of a jet aimed at a house, barn, automobile, or other valuable property. They have even been seen breaking loose from their mountings and rolling down hills scattering fire on the way. The safest practice is to have a professional install these tanks so that they are not only safe from fire themselves but will not endanger life or other valuable property in case they do become overheated (Alger 1971).

Proposed Standards:

  1. Hydrocarbon fuel tanks should be installed only by persons licensed to do so and under permit. They should not be placed in operation until approved by a fire marshall.
  2. Store gasoline only in properly vented underground tanks.
  3. Do not mount fuel oil tanks on the side of the residence or within 15 feet of any structure.
  4. Mount LPG tanks on concrete or steel cradles that will not allow the tank to roll; if they are not spherical, orient them so that neither end points toward any structure and, regardless of shape, so that the relief valve does not point at any structure.
  5. Require all hydrocarbon fuel tanks to have, properly maintained, the same amount of vegetative clearing as residences and other structures in the same wildfire hazard severity class area.
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