Homeowner Wildfire Assessment Glossary

Class A Roof: Effective against severe fire test exposures. Under such exposures, roof coverings of this class are not readily flammable, afford a fairly high degree of fire protection to the roof deck, do not slip from position, and are not expected to produce flying brands.

Class B Roof: Effective against moderate fire test exposures. Under such exposures, roof coverings of this class are not readily flammable, afford a moderate degree of fire protection to the roof deck, do not slip from position, and are not expected to produce flying brands.

Class C Roof: Effective against light fire test exposure. Under such exposures, roof coverings of this class are not readily flammable, afford a measurable degree of fire protection to the roof deck, do not slip from position, and are not expected to produce flying brands. Class C is the minimum level required by law.

Building: Any structure used or intended for supporting or sheltering any use or occupancy that is defined in the latest adopted edition of the California Building Code, except Group U, Division 1, Occupancy. "Building" includes mobile homes and manufactured homes, churches, and day care facilities.

CDF: California Department of Forestry and Fire Protection.

Clearance: Space cleared of vegetation as required by law, regulation, easement, etc., for the purpose of preventing fires.

Combustible: Materials capable of quickly igniting.

Crown: The upper part of a tree, which includes the branches and leaves.

Defensible Space: The area within the perimeter of a parcel, development, neighborhood, or community where basic wildland fire protection practices and measures are implemented, providing the key point of defense from an approaching wildfire or defense against encroaching wildfires or escaping structure fires. The area is characterized by the establishment and maintenance of emergency vehicle access, emergency water reserves, street names and building identification, and fuel modification measures. In simplest terms, it is adequate space between structures and flammable vegetation, which allows firefighters a safe working area in which they can attack an oncoming wildfire.

Detached Structure: Any structure located on a property that is not attached to the principal dwelling. These can include garages, sheds, fences, carports, barns, silos, decks, and many others.

Driveway: A vehicular access that serves no more than two buildings, with no more than three dwelling units on a single parcel, and any number of accessory buildings.

Eaves: The part of a roof that overhangs the outside walls of your home.

Egress: A way or ways by which residents and/or fire equipment may exit an area in the event of a fire emergency.

Ember: A hot fragment of wood or coal that is left from a fire and is glowing or smoldering. Burning embers, i.e., firebrands, can rise out of a vegetative fire and travel up to one mile downwind where it can land on combustible material, enter a structure, or ignite vegetation near a structure.

FEMA: Federal Emergency Management Agency.

Fire Danger: An assessment of both fixed and variable factors of the fire environment, which determine the ease of ignition, rate of spread, difficulty of control, and the fire impact.

Fire Hazard: Something that burns or causes fires to burn hotter or faster, e.g., vegetative and non-vegetative fuels, fuel conditions, weather, and topography.

Fire Hazard Mitigation: Various methods by which existing fire hazards can be reduced in a certain area, such as fuel breaks, non-combustible roofing, spark arresters, etc.

Fire History: The known frequency and intensity of fires that have occurred in a given area over a period of time.

Fire Risk: A quantitative measure of the likelihood of a fire event at a given point of interest.

Fire Safe: A term that has come to mean "taking into consideration fire risks and hazards, and acting to mitigate them." Also, an environment created in and around a building to resist the intrusion of fire.

Fire Suppression: All activities concerned with controlling and extinguishing a fire following its detection. Synonymous with fire control.

Fire Threat: A qualitative measure of fire danger (for example, a fire may pose a high threat to a given house).

Fire Weather: Frequency and intensity of weather that contributes to fire occurrence, such as high temperatures, low precipitation, and high winds.

Flame Impingement: Or "direct flame", is the striking of flame against an object.

Flammable: Self-heating or reactive materials that may quickly ignite.

Fuel: Anything that will burn easily, such as vegetation and wood frame structures.

Fuelbreak: An existing barrier or change in fuel type (to one that is less flammable than that surrounding it), or a wide strip of land on which the native vegetation has been modified or cleared, that acts as a buffer to fire spread so that fires burning into them can be more readily controlled. Often selected or constructed to protect a high value area from fire.

Ingress: A way or ways by which residents and/or fire equipment may enter an area in the event of a fire emergency.

Intermix (Intermix/Interface, or Wildland Intermix): Interspersing of developed land with wildland, where there are no easily discernible boundaries between the two systems. An example would be what real estate brochures describe as "ranchettes" or "weekend farmer" homes. Intermix poses more problems in wildland fire management than interface.

Ladder Fuels: Live and dead plant materials that provide a link between the surface fuels and crown fuels in a tree stand, thus contributing to the ease of torching and crowning. Understory shrubs, attached dead stems on dominant and suppressed trees, and canopies of small understory trees form the majority of ladder fuels.

Mitigation: To moderate in force or intensity; an effort at reducing or eliminating the impacts of injury or damage from a hazard or disaster.

Non-Combustible: Non-flammable.

Ornamentals: Landscaping items that possess dense foliage or volatile oils that may serve to increase the fire risk to a nearby structure.

Radiant Heat: The heat given off by burning vegetation which can then be transferred to another body not in contact. Radiant heat can ignite combustible materials or make them more readily ignitable by preheating the exposed material.

Roof Covering: The shingles, tiles, or other top layer of a roof assembly.

Soffit: The exposed underside of any overhanging element (e.g. roof, arch) of a building.

Spark Arrester: A device designed to keep sparks from escaping, as at a chimney opening.

Structure: That which is built or constructed. An edifice or building of any kind, or any piece of work artificially built up or composed of parts joined together in some definite manner.

Stucco: Traditional stucco is a cement mixture used for siding, usually on Mission or other Spanish style homes. The cement is combined with water and inert materials, such as sand and lime. Usually, wooden walls are covered with tar paper and chicken wire or galvanized metal screening. This framework is then covered with the stucco mixture. Sometimes, the cement mix is applied directly to specially prepared masonry surfaces. Exterior construction materials such as brick and stucco resist fire much better than wood.

Vulnerability: In the case of wildfire, vulnerability is the susceptibility of a structure, specific components of a structure, and/or site fuels to a wildfire ignition.

Wildland-Urban Interface: Any area containing human developments that may be threatened by wildland fires.