SECTION 4401 GENERAL
4401.1 Purpose. The purpose of this chapter is to establish minimum design and construction standards for the protection of life and property from fire, within the Urban Wildland Interface. These provisions are meant to aid in the prevention and suppression of fires, and lessen the hazards to structures from wildland fires as well as the hazards to wildlands from structure fires.

4401.2 Scope. All new building construction, including any additions that increase a building’s habitable floor area or number of stories, shall comply with the provisions of this chapter.
EXCEPTION: Temporary buildings and buildings or structures used for the sole purpose of providing shelter for agricultural implements, farm products, livestock or poultry.

back to top

SECTION 4402 DEFINITIONS
For the purpose of this chapter, certain terms are defined as follows:

ADEQUATELY MANNED STATION is a fire station having an average daily manning of at least three fire fighters.

BUILDING SIZE as referenced in Section 4404 is the total floor area, as defined in section R202, of all buildings located on the same property. The area of an attached garage may be excluded from the total floor area provided the garage is separated from the dwelling by a full one-hour fire barrier. A building that is at least 50 feet away from another building shall be considered separately in computing building size. Covered areas that are at least 50% open on two or more sides shall not be included in the computation of total floor area.

DEFENSIBLE SPACE is a designated area surrounding a building or buildings, subject to approved fuel modification measures, intended to reduce fire-spread potential between the structure and wildland.

Defensible Space shall extend to the distances specified in Table 44-A (a minimum 30 feet for flat lots), or to the property lines, whichever is less.

Defensible Space measurements shall commence from the building plane, and follow all projections and recessions on each side of the building. If a defensible space is required under these provisions for one building or structure, then that mandatory defensible space shall also encompass all appropriate buildings on the property located within a 50 foot radius of the affected building. For any additions to an existing structure, the defensible space shall be provided around the entire structure, including the addition.

Within a defensible space, the following mitigation measures shall be provided, subject to the exceptions contained herein:

1. All slash and flammable debris shall be removed from all areas of a defensible space, except as otherwise expressly designated by the inspector (for example, small amounts may remain for habitat).
   EXCEPTION: Firewood may be stored as follows: up to ten cubic feet – unregulated; stacks larger than ten cubic feet - minimum 10 foot distance from the structure;
   
   
2. All trees and shrubs located within 10 feet of the structure(s) shall be removed.
   EXCEPTION: A tree or shrub may remain within ten feet, provided the defensible space distance is measured commencing from the tree’s drip edge rather than from the building plane (so the tree is considered part of or an extension of the structure), and provided the distance is not limited by a property line.
   
   
3. Trees and shrubs over 5 feet tall shall have an average crown spacing of 10 feet from tree to tree. Groupings of trees may be allowed, provided that all of the crowns in such group of trees are at least 10 feet from the structure, and provided that the overall average tree spacing within the defensible space is 10 feet (i.e. tree spacing around the grouping is greater than 10’).
   EXCEPTIONS:
   (1) Aspens, narrowleaf cottonwoods, willows, and other trees and shrubs listed in CSU Cooperative Extension publication 6.305 Firewise Plant Materials, that are 10 or more feet from the structure may be spaced closer than ten feet if expressly approved by the inspector.
   
   (2) Closer spacing of any trees may be allowed by the inspector upon a determination that a 10-foot average spacing would put the remaining trees at undue risk of wind-throw or snow breakage.
   
   
4. Trees remaining within the defensible space shall have branches pruned to a height of 10 feet, but notwithstanding said height requirement, branches need not be pruned to more than 1/3 of the tree height.
   EXCEPTIONS:
   (1) Aspen trees.
   
   (2). Isolated spruce and fir trees that are at least 10 feet from the structure measured from the tree’s drip edge.
   
   

back to top

FIRE-RESISTIVE CONSTRUCTION shall be defined as any one of the following:
Fire-resistive shell – exterior walls shall be a listed, one-hour fire-resistive assembly, or log (6” min. dia.), and the roof shall be protected by a layer of 5/8” type X gypsum board ceiling or nominal 2”x T&G wood ceiling. A non-combustible exterior wall surface (cement stucco, brick, stone, cement fiber siding) may be used in lieu of the exterior membrane of a listed wall assembly.Non-combustible construction – wall, floor, and roof framing, columns and beams shall be of steel, concrete or masonry

MONITORED SMOKE ALARM SYSTEM shall be defined, permitted and inspected through the responding fire district.

MUNICIPAL-TYPE WATER SUPPLY HYDRANT shall be defined as a water supply hydrant that has the capacity to furnish, over and above domestic consumption, a minimum flow of 1000 gpm and 20 psi residual pressure for a two-hour duration.

RESPONSE ZONE represents the routine driving time from an adequately manned station under optimal driving conditions, as determined by the fire department, as follows: Zone 1-2: 5 minutes or less; Zone 3-4: more than 5 minutes

TREE CROWN is the needle or leaf bearing part of a tree. The crown edge is the tree’s drip edge.

back to top

SECTION 4403 HAZARD RATINGS
Wildfire hazard rating. The Colorado State Forest Service shall assign each subdivision, or portion thereof, a Wildfire Hazard Rating of “low”, “moderate” or “high”. The rating will determine the mitigation required for the construction. The rating is based on criteria such as topography and type and extent of vegetation. However, any subdivision located within response zone 1-2, that is served by approved municipal water supply hydrants, and that is served by year-round maintained roads which have an all weather surface at least 22’ wide, will automatically receive a rating of low. For any subdivision to receive consideration for an automatic low hazard rating, all hydrants on such property must be municipal type water supply hydrants as defined, must be located throughout the subdivision or portion thereof and the hydrant spacing must be an average of not more than 500 feet.

back to top

SECTION 4404 REQUIRED MITIGATION
Class A Roof. All new construction, including additions, regardless of the designated response zone or the wildfire hazard rating assigned to the property, shall be provided with a class A roof as defined in R902.

Low Hazard. Construction in an area with a “Low” Fire Hazard Rating shall require no additional mitigation measures beyond the installation of a Class A roof.

Moderate Hazard. Construction in an area with a “Moderate” Fire Hazard Rating shall provide a defensible space area in accordance with the requirements of this chapter and Table 44-A. Additionally, based upon the higher fire loading potential, structures 6000 square feet and larger in building size shall be provided with an automatic sprinkler system, and structures 4000 s.f. to 6000 s.f. in building size shall implement a fire-resistive construction measure as defined herein.

High Hazard. Construction in an area with a “High” Fire Hazard Rating shall provide a defensible space area in accordance with the requirements of this chapter and Table 44-A. Additionally, structures 4000 square feet and larger in building size shall be provided with an automatic sprinkler system, and structures ranging from 2400 s.f. up to 4000 s.f. in building size shall implement a fire-resistive construction measure as defined herein.

Additions. An addition located in a high or moderate wildfire hazard rated subdivision, added to any structure built before January 1, 2000, will require that a defensible space be provided around the addition as well as the existing structure, in accordance with the requirements of this chapter and Table 44-A. If the building size of the addition itself would require fire-resistive construction by this chapter, the addition shall be of fire-resistive construction but not the existing structure. If the building size of the addition itself would require a sprinkler system under this chapter, the entire building, including the additions, the existing structure and any other applicable structures must be equipped with a sprinkler system. An addition to a building that was previously required to be of fire resistive construction or was required to have a sprinkler system or monitored smoke detector system installed, will require the same level of protection.

Alternates and Exceptions to Section 4404.
1) Unless otherwise required by this code, an automatic sprinkler system may be installed in lieu of required fire-resistive construction.

2) A monitored smoke alarm system may be provided in lieu of fire-resistive construction.

3) Alternate materials and methods, such as installing a draft hydrant in lieu of fire-resistive construction, may be considered by the Building Department in accordance with section R104.11 in its discretion on a case by case basis.

4) Structures located in subdivisions that implement a CSFS approved subdivision-wide fuel-reduction plan or defensible space plan will not require individual defensible spaces.

back to top

TABLE 44-A --MINIMUM DEFENSIBLE SPACE DISTANCES
The minimum defensible space distance shall be 30 feet on level terrain, plus modification to recognize the increased rate of fire spread at sloped sites. Minimum distances for Defensible Space shall be directly from this table or to the lot line, whichever is less.