Chapter 51-55 WAC:

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Chapter 51-55 WAC

Last Update: 11/15/23

STATE BUILDING CODE ADOPTION AND AMENDMENT OF THE 2021 EDITION OF THE WILDLAND-URBAN INTERFACE CODE

WAC Sections

HTML PDF	51-55-001	Authority.
HTML PDF	51-55-002	Purpose.
HTML PDF	51-55-003	International Wildland-Urban Interface Code.
HTML PDF	51-55-008	Implementation.
HTML PDF	51-55-0100	Scope and administration.
HTML PDF	51-55-0200	Chapter 2—Definitions.
HTML PDF	51-55-0300	Wildland-urban interface areas.
HTML PDF	51-55-0400	Wildland-urban interface area requirements.
HTML PDF	51-55-0500	Special building construction regulations.
HTML PDF	51-55-0600	Fire protection requirements.
HTML PDF	51-55-0700	Chapter 7—Vegetation management plan.
HTML PDF	51-55-0800	Chapter 8—Fire hazard severity form.
HTML PDF	51-55-0900	Chapter 9—Fire danger rating system.
HTML PDF	51-55-1000	Chapter 10—Referenced standards.

PDF51-55-001

Authority.

These rules are adopted under the authority of chapter 19.27 RCW.

[Statutory Authority: RCW 19.27.031, 19.27.074, and 19.27.560. WSR 23-02-056, 23-12-109, and 23-20-028, § 51-55-001, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24.]

PDF51-55-002

Purpose.

The purpose of these rules is to implement the provisions of chapter 19.27 RCW, which provides that the state building code council shall maintain the state building code in a status which is consistent with the purpose as set forth in RCW 19.27.020. In maintaining the codes the council shall regularly review updated versions of the codes adopted under the act, and other pertinent information, and shall amend the codes as deemed appropriate by the council.

[Statutory Authority: RCW 19.27.031, 19.27.074, and 19.27.560. WSR 23-02-056, 23-12-109, and 23-20-028, § 51-55-002, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24.]

PDF51-55-003

International Wildland-Urban Interface Code.

The 2021 edition of the International Urban-Interface Code, published by the International Code Council, is hereby adopted by reference with the following additions, deletions, and exceptions.

[Statutory Authority: RCW 19.27.031, 19.27.074, and 19.27.560. WSR 23-02-056, 23-12-109, and 23-20-028, § 51-55-003, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24.]

PDF51-55-008

Implementation.

The International Wildland-Urban Interface Code adopted by this chapter shall become effective in all counties and cities of this state on March 15, 2024.

[Statutory Authority: RCW 19.27.031 and 19.27.074. WSR 23-23-107, § 51-55-008, filed 11/15/23, effective 3/16/24. Statutory Authority: RCW 19.27.031, 19.27.074, and 19.27.560. WSR 23-02-056, 23-12-109, and 23-20-028, § 51-55-008, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24.]

PDF51-55-0100

Scope and administration.

101 Scope and general requirements.

101.2 Scope. The provisions of this code shall apply to the construction, alteration, movement, repair, maintenance and use of any building, structure, or premises within the wildland-urban interface areas in this jurisdiction.

Buildings or conditions in existence at the time of the adoption of this code are allowed to have their use or occupancy continued, if such condition, use or occupancy was legal at the time of the adoption of this code, provided that such continued use does not constitute an egregious danger to life or property.

Buildings or structures moved into or within the jurisdiction shall comply with the provisions of this code for new buildings or structures.

101.4 Retroactivity. The provisions of the code shall apply to conditions arising after the adoption thereof, conditions not legally in existence at the adoption of this code and conditions that, as determined by the code official, constitute an egregious hazard to life or property.

EXCEPTION:

Provisions of this code that specifically apply to existing conditions are retroactive.

[Statutory Authority: RCW 19.27.031, 19.27.074, and 19.27.560. WSR 23-02-056, 23-12-109, and 23-20-028, § 51-55-0100, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24.]

PDF51-55-0200

Chapter 2—Definitions.

202 Definitions.

ACCESSORY STRUCTURE. A building or structure used to shelter or support any material, equipment, chattel or occupancy other than a habitable building, or a habitable building or structure that is accessory to and incidental to that of the dwelling(s) and that is located on the same lot.

BUILDING OFFICIAL. Not adopted.

EGREGIOUS DANGER. A danger that if left unmitigated, places the occupants or property in immediate danger.

FUEL, HEAVY. Vegetation consisting of round wood 3 to 8 inches (76 to 203 mm) in diameter. See Fuel Models G, I, J, K, and U described in Chapter 9.

FUEL, LIGHT. Vegetation consisting of herbaceous plants and round wood less than 1/4-inch (6.4 mm) in diameter. See Fuel Models A, C, E, L, N, P, R, and S described in Chapter 9.

FUEL, MEDIUM. Vegetation consisting of round wood 1/4 to 3 inches (6.4 mm to 76 mm) in diameter. See Fuel Models B, D, F, H, O, Q, and T described in Chapter 9.

HIGH-DENSITY VEGETATED AREA. An area defined by a square determined in accordance with Section 302.3.1, with 75 percent or more vegetation.

WASHINGTON WILDLAND-URBAN INTERFACE MAP (WA-WUI). The Washington department of natural resources map designating urban areas, wildland-urban interface, wildland-urban intermix, wildlands, and long-term nonbuildable areas, designated as the Washington wildland-urban interface as mapped for 2019 by the Washington state department of natural resources—wildfire and forest health divisions under consultation from the USFS Rocky Mountain Research Station.

WILDLAND-URBAN INTERFACE/INTERMIX AREA. That geographical area where structures and other human development meets or intermingles with wildland or vegetative fuels.

[Statutory Authority: RCW 19.27.031, 19.27.074, and 19.27.560. WSR 23-02-056, 23-12-109, and 23-20-028, § 51-55-0200, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24]

PDF51-55-0300

Wildland-urban interface areas.

301 General.

301.1 Scope. Wildland urban interface areas shall be determined using the Washington wildland urban interface map (WA-WUI). WA-WUI designations are permitted to be modified, upon approval of a finding of fact in accordance with Section 302.

User note: The WA-WUI map is available at https://geo.wa.gov/maps/786aaa1dbbd748e6ae04bc43c8f127fe/explore.

301.2 Construction in wildland-urban interface or intermix areas. Where a structure is proposed to be constructed in an area designated by the WA-WUI map as wildland-urban interface or intermix, the construction shall comply with the provisions of this code.

301.3 Construction in wildlands areas. Where a structure is proposed to be constructed in an area designated by the WA-WUI map as wildlands, the applicable wildland urban interface area designation shall be based on a finding of fact in accordance with Section 302.

302 Wildland-urban interface area designations.

302.1 General. Wildland urban interface area designations are permitted to be established in accordance with this section.

302.2 Finding of fact. The applicable wildland urban interface designation shall be based on a finding of fact. The finding of fact shall comply with the provisions of Appendix E or is permitted to be based on the worksheet and procedures in Section 302.3.

302.3 Simplified wildland urban interface designation worksheet. The wildland urban interface designation is permitted to be established using the procedure outlined in Table 302(1), using the worksheet in Table 302(2).

302.3.1 Area to be evaluated. For the purposes of establishing structure and vegetation densities, the area covered by a square of 1320 feet on a side (40 acres) shall be evaluated. The square area shall be located such that the site under consideration is in its center, except where the square would overlap a water body shown on the WA-WUI map with a surface area greater than 200,000 square feet, the location shall be adjusted such that no part of the square overlaps the water body.

Table 302.3(1)

Outline of Simplified Procedure for Determining Wildland Interface Designation

For the area to be evaluated in Section 302.3.1:

1. Determine structure density category (uninhabited, very low, low, medium, or high).

2. Determine vegetation density category (nonvegetated or vegetated).

3. Determine proximity category (near or distant).

4. Based on structure density, vegetation density, and proximity categories, determine if compliance with this code is required (WUIC applies, WUIC does not apply).

5. Where compliance with this code is required, determine wildland urban interface area designation (intermix or interface).

302.3.2 Structure density category. The structure density category shall be determined by counting the number of structures within the area to be evaluated per Section 302.3.1. The structure density category shall be determined as follows:

UNINHABITED:	0 structures
VERY LOW:	1 structure
LOW:	2 to 8 structures
MEDIUM:	9 to 120 structures
HIGH:	more than 120 structures

302.3.3 Vegetation density category. Vegetation coverage within the area to be evaluated per Section 302.3.1 shall be determined in accordance with Chapter 9. Vegetation density shall be determined by dividing the vegetation coverage by 1,742,400 square feet (40 acres). Where the vegetation density is less than 50 percent, the vegetation density category for the site shall be nonvegetated. Where the vegetation density is 50 percent or more, the vegetation density category for the site shall be vegetated.

302.3.4 Proximity category. The distance from the site being evaluated to a high-density vegetated area shall be measured from the closest edge of the site boundary to the closest edge of the nearest high-density vegetated area. Where the distance is less than 1.5 miles, the proximity category shall be near. Where the distance is 1.5 miles or more, the proximity category shall be distant.

302.3.5 WUIC applicability. The WUIC shall apply, and the site shall be designated as intermix or interface in accordance with Section 302.3.6 under either of the following conditions:

1. The structure density category is very low to high, and the vegetation density category is vegetated.

2. The structure density category is very low to high, and the proximity category is near.

The WUIC shall not apply under either of the following conditions:

1. The structure density category is uninhabited, and the site is not located within an area designated as intermix or interface on the WA-WUI map.

2. The structure density category is uninhabited to high, the vegetation density category is nonvegetated, and the proximity category is distant.

302.3.6 Wildland urban interface area designation. Where required by Section 302.3.5, the site shall be designated as intermix or interface in accordance with Section 302.3.6.1 or 302.3.6.2.

302.3.6.1 Intermix designation. The site shall be designated as intermix where the structure density category is very low to high, and the vegetation density category is vegetated.

302.3.6.2 Interface designation. The site shall be designated as interface where the structure density category is very low to high, and the proximity category is near.

Table 302(1). Outline of simplified procedure for determining wildland interface designation

1. Determine structure density category in accordance with Section 302.3.2. Numbers in table are the number of structures within the area determined by Section 302.3.1.
UNINHABITED	VERY LOW	LOW	MEDIUM	HIGH
0	1	2 TO 8	9 TO 120	MORE THAN 120

2. Determine vegetation density category within the area determined by Section 302.3.1.
	NONVEGETATED	VEGETATED
	Less than 50% vegetated	50% or more vegetated

3. Determine proximity category to the nearest high-density vegetated area.
	NEAR	DISTANT
	Less than 1.5 mi (2.414 km)	1.5 mi (2.414 km) or more

4. Use structure density, vegetation density, and proximity categories from above to determine if WUIC applies.
	WUIC Applies	WUIC Does Not Apply
	• Structure density category is very low to high; and	• Structure density category is uninhabited; and
	• Vegetation density category is vegetated.	• The site is not located within an area designated as intermix or interface on the WA-WUI map.
	• Structure density category is very low to high; and	• Structure density category is uninhabited to high; and
	• Proximity category is near.	• Vegetation density category is nonvegetated; and
		• Proximity category is distant.

5. Where WUIC applies, the site shall be designated as intermix or interface as follows:
	INTERMIX	INTERFACE
	• Structure density category is very low to high; and	• Structure density category is very low to high; and
	• Vegetation density category is vegetated.	• Proximity category is near.

Table 302(2). Worksheet for simplified procedure for determining wildland interface designation

302.4 Review of wildland-urban interface areas. The code official shall review for approval evaluated areas for new or modified findings of fact. Where a new or modified findings of fact are approved, the code official shall recommend to WADNR a modification to the wildland-urban interface areas mapping.

[Statutory Authority: RCW 19.27.031 and 19.27.074. WSR 23-23-107, § 51-55-0300, filed 11/15/23, effective 3/16/24. Statutory Authority: RCW 19.27.031, 19.27.074, and 19.27.560. WSR 23-02-056, 23-12-109, and 23-20-028, § 51-55-0300, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24.]

PDF51-55-0400

Wildland-urban interface area requirements.

401 General.

401.1 Scope.Wildland-urban interface areas shall be provided with emergency vehicle access and water supply in accordance with this chapter.

401.2 Objective. This section is not adopted.

401.3 General safety precautions. This section is not adopted.

402 Applicability.

402.1 Subdivisions. Subdivisions shall comply with locally adopted standards.

402.1.1 Access. This section is not adopted.

402.1.2 Water supply. This section is not adopted.

402.2 Individual structures. Individual structures shall comply with Sections 402.2.1 and 402.2.2.

402.2.1 Access. Individual structures hereafter constructed or relocated into or within wildland-urban interface areas shall be provided with driveways in accordance with Section 403.2 and locally adopted standards. Marking of fire protection equipment shall be provided in accordance with Section 403.5 and address markers shall be provided in accordance with Section 403.6.

402.2.2 Water supply. Individual structures hereafter constructed or relocated into or within wildland-urban interface areas shall be provided with a conforming water supply in accordance with locally adopted standards.

EXCEPTION:

Not adopted.

402.3 Existing conditions. This section is not adopted.

403 Access.

403.2.1 Dimensions. This section is not adopted.

403.2.2 Length. This section is not adopted.

403.2.3 Service limitations. This section is not adopted.

403.2.4 Turnarounds and turnouts.Driveways in excess of three hundred feet in length shall be provided with turnarounds. Driveways in excess of five hundred feet in length and less than twenty feet in width shall be provided with turnouts and turnarounds. Turnarounds and turnouts shall be designed as required by locally adopted standards.

403.2.5 Turnouts. This section is not adopted.

403.3 Fire apparatus access road. Where required, fire apparatus access roads shall be provided and maintained as required by locally adopted street, road, and access standards.

403.4 Marking of roads. This section is not adopted.

403.4.1 Sign construction. This section is not adopted.

404 Water supply.

404.1 General. Water supply shall be provided and maintained as required by locally adopted standards.

404.2 Water sources. This section is not adopted.

404.3 Draft sites. This section is not adopted.

404.3.1 Access. This section is not adopted.

404.3.2 Pumper access points. This section is not adopted.

404.4 Hydrants. This section is not adopted.

404.5 Adequate water supply. This section is not adopted.

404.6 Fire department. This section is not adopted.

404.7 Obstructions. This section is not adopted.

404.8 Identification. This section is not adopted.

404.9 Testing and maintenance. This section is not adopted.

404.10 Reliability. This section is not adopted.

404.10.1 Objective. This section is not adopted.

404.10.2 Clearance of fuel. This section is not adopted.

404.10.3 Standby power. This section is not adopted.

[Statutory Authority: RCW 19.27.031, 19.27.074, and 19.27.560. WSR 23-02-056, 23-12-109, and 23-20-028, § 51-55-0400, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24.]

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Special building construction regulations.

Section 501 General.

501.1 General. Buildings and structures hereafter constructed, modified, or relocated into or within the wildland-urban interface area shall meet the construction requirements of Sections 501.4 through 501.8.

EXCEPTIONS:	1. Buildings and structures with fire hazard severity determined in Section 502 and with ignition-resistant construction classification determined in Section 503.
	2. Accessory structures not exceeding 200 square feet (18.5 m2) in floor area and where located not less than 50 feet (15,240 mm) from buildings or structures containing habitable spaces.
	3. Agricultural buildings located not less than 50 feet (15,240 mm) from buildings or structures containing habitable spaces.

501.2 Objective. This section is not adopted.

501.4 Roof covering. Roofs shall have a roof assembly that complies with a Class A rating when tested in accordance with ASTM E108 or UL 790. For roof assemblies where the profile allows a space between the roof covering and roof deck, the space at the eave ends shall be firestopped to preclude entry of flames or embers or have one layer of 72-pound (32.4 kg) mineral-surfaced, nonperforated cap sheet complying with ASTM D3909 installed over the combustible roof deck.

EXCEPTIONS:	1. Class A roof assemblies including those with coverings of brick, masonry, or an exposed concrete roof deck.
	2. Class A roof assemblies also include ferrous or copper shingles or sheets, metal sheets and shingles, clay or concrete roof tile or slate installed on noncombustible decks or ferrous, copper or metal sheets installed without a roof deck on noncombustible framing.
	3. Class A roof assemblies include minimum 16 oz/sq. ft. (0.0416 kg/m2) copper sheets installed over combustible roof decks.

501.4.1 Roof valleys. Where provided, valley flashings shall be not less than 0.019-inch (0.48 mm) (No. 26 galvanized sheet gage) corrosion-resistant metal installed over a minimum 36-inch-wide (914 mm) underlayment consisting of one layer of 72-pound (32.4 kg) mineral-surfaced, nonperforated cap sheet complying with ASTM D3909 running the full length of the valley.

501.5 Exterior walls and projections other than decks. Exterior walls and projections other than decks, of buildings, or structures, or accessory structures attached to buildings or structures with habitable spaces, shall be constructed with one of the following methods, with materials extending from the top of the foundation to the underside of the roof sheathing:

1. Materials approved for not less than one hour fire-resistance rated construction on the exterior side;

2. Approved noncombustible materials;

3. Heavy timber or log wall construction;

4. Fire-retardant-treated wood on the exterior side. The fire-retardant-treated wood shall be labeled for exterior use and meet the requirements of Section 2303.2 of the International Building Code; or

5. Ignition-resistant materials, complying with Section 503.2 on the exterior side.

EXCEPTION:

Unenclosed accessory structures attached to buildings with habitable spaces and projections, such as decks, attached to the first floor of a building, if when the structure is built with building materials at least two inches nominal depth and the area below the unenclosed accessory structure is screened with material with openings no greater than 1/4-inch maximum to prevent accumulation of combustibles and to prevent embers from coming in underneath.

501.6 Decks and appendages. The material of decks, porches, balconies, and stairs shall be constructed with any of the following materials:

1. Ignition-resistant material that complies with the minimum performance requirement of Section 503.2.

2. Exterior fire-retardant-treated wood.

3. Noncombustible material.

4. Any material that complies with the minimum performance requirements of Section 503.2 when attached exterior wall covering is also either noncombustible or ignition-resistant material.

5. Heavy timber construction consisting of the following:

5.1. Posts shall be a minimum of 6 inches x 6 inches nominal dimension.

5.2. Beams shall be a minimum of 6 inches x 8 inches nominal dimension.

5.3. Joists shall be a minimum of 4 inches x 8 inches nominal dimension spaced at no greater than 24 inches on center.

501.6.1 Clearance. Decks with less than 48 inches of clearance from finished grade to deck joists shall be enclosed with screen material with openings no greater than 1/4-inch maximum to prevent accumulation of combustibles and to prevent embers from coming in underneath.

501.6.2 Walking surfaces. The walking surface material of decks, porches, balconies, and stairs shall be constructed with one of the following materials:

1. Ignition-resistant material that complies with the performance requirements of Section 503.2.

2. Exterior fire-retardant-treated wood.

3. Noncombustible material.

4. Where the deck, porch, balcony, or stairs are constructed of heavy timber in accordance with Section 501.6, natural wood decking products shall be:

4.1. 2-inch nominal dimension lumber; or

4.2. 1 1/4-inch nominal hardwood (i.e., teak, mahogany, or other approved hardwood).

5. Material that complies with the performance requirements of Section 501.6.2.1 when tested in accordance with ASTM E2632 and when attached exterior wall covering is also composed of only noncombustible or ignition-resistant materials.

EXCEPTION:

Wall material shall be permitted to be of any material that otherwise complies with Section 501.5 when the decking surface material complies with the performance requirements of ASTM E84 with a Class B flame spread index.

501.6.2.1 Material in Section 501.6.2, Item 5. The walking surface material shall be tested in accordance with ASTM E2632 and shall comply with the following condition of acceptance. The ASTM E2632 test shall be conducted on a minimum of three test specimens and the peak heat release rate shall be less than or equal to 25 kW/ft2 (269 kW/m2). If any one of the three tests does not meet the conditions of acceptance, three additional tests shall be run. All the additional tests shall meet the condition of acceptance.

501.7 Exterior glazing. Exterior windows, window walls and glazed doors, windows within exterior doors, and skylights shall be tempered glass, multilayered glazed panels, glass block, or have a fire protection rating of not less than 20 minutes.

501.8 Vents. Attic ventilation openings, foundation or underfloor vents, or other ventilation openings in vertical exterior walls and vents through roofs shall not exceed 144 square inches (0.0929 m2) each. Such vents shall be covered with noncombustible corrosion-resistant mesh with openings not to exceed 1/4 inch (6.4 mm), or shall be designed and approved to prevent flame or ember penetration into the structure.

1. Attic ventilation openings shall not be located in soffits, in eave overhangs, between rafters at eaves, or in other overhang areas. Gable end and dormer vents shall be located not less than 10 feet (3048 mm) from lot lines. Underfloor ventilation openings shall be located as close to grade as possible.

502 Fire hazard severity.

502.1 General. The fire hazard severity of building sites for buildings hereafter constructed, modified, or relocated into wildland-urban interface areas shall be established in accordance with Table 502.1. See also Chapter 8.

502.2 Fire hazard severity reduction. The fire hazard severity identified in Table 502.1 is allowed to be reduced by implementing a vegetation management plan in accordance with Chapter 7.

TABLE 502.1

FIRE HAZARD SEVERITY

(No change to the table)

504 Class 1 ignition-resistant construction.

504.7 Appendages and projections.Accessory structures attached to buildings with habitable spaces and projections other than decks, porches, balconies, or stairs, shall be not less than 1-hour fire-resistance-rated construction, heavy timber construction, or constructed of one of the following:

1. Approved noncombustible materials.

2. Fire-retardant-treated wood identified for exterior use and meeting the requirements of Section 2303.2 of the International Building Code.

3. Ignition-resistant building materials in accordance with Section 503.2.

EXCEPTION:

Not adopted.

504.8 Decks and appendages. The material of decks, porches, balconies, and stairs shall be constructed with any of the following materials:

1. Ignition-resistant material that complies with the minimum performance requirement of Section 503.2.

2. Exterior fire-retardant-treated wood.

3. Noncombustible material.

4. Any material that complies with the minimum performance requirements of Section 503.2 when attached exterior wall covering is also either noncombustible or ignition-resistant material.

5. Heavy timber construction consisting of the following:

5.1. Posts shall be a minimum of 6 inches x 6 inches nominal dimension.

5.2. Beams shall be a minimum of 6 inches x 8 inches nominal dimension.

5.3. Joists shall be a minimum of 4 inches x 8 inches nominal dimension spaced at no greater than 24 inches on center.

504.8.1 Clearance. Decks with less than 48 inches of clearance from finished grade to deck joists shall be enclosed with screen material with openings no greater than 1/4-inch maximum to prevent accumulation of combustibles and to prevent embers from coming in underneath.

504.8.2 Walking surfaces. The walking surface material of decks, porches, balconies, and stairs shall be constructed with one of the following materials:

1. Ignition-resistant material that complies with the performance requirements of Section 503.2.

2. Exterior fire-retardant-treated wood.

3. Noncombustible material.

4. Where the deck, porch, balcony, or stairs are constructed of heavy timber in accordance with Section 501.6, natural wood decking products shall be:

4.1. 2-inch nominal dimension lumber; or

4.2. 1 1/4-inch nominal hardwood (i.e., teak, mahogany, or other approved hardwood).

5. Material that complies with the performance requirements of Section 504.8.2.1 when tested in accordance with ASTM E2632 and when attached exterior wall covering is also composed of only noncombustible or ignition-resistant materials.

EXCEPTION:

504.8.2.1 Material in Section 504.8.2, Item 5. The walking surface material shall be tested in accordance with ASTM E2632 and shall comply with the following condition of acceptance. The ASTM E2632 test shall be conducted on a minimum of three test specimens and the peak heat release rate shall be less than or equal to 25 kW/ft2 (269 kW/m2). If any one of the three tests does not meet the conditions of acceptance, three additional tests shall be run. All the additional tests shall meet the condition of acceptance.

504.9 Exterior glazing. Exterior windows, window walls and glazed doors, windows within exterior doors, and skylights shall be tempered glass, multilayered glazed panels, glass block or have a fire protection rating of not less than 20 minutes.

504.10 Exterior doors. Exterior doors shall be approved noncombustible construction, solid core wood not less than 1 3/4 inches thick (44 mm), or have a fire protection rating of not less than 20 minutes. Windows within doors and glazed doors shall be in accordance with Section 504.8.

EXCEPTION:

Vehicle access doors.

504.11 Vents. Attic ventilation openings, foundation or underfloor vents, or other ventilation openings in vertical exterior walls and vents through roofs shall not exceed 144 square inches (0.0929 m2) each. Such vents shall be covered with noncombustible corrosion-resistant mesh with openings not to exceed 1/4 inch (6.4 mm), or shall be designed and approved to prevent flame or ember penetration into the structure.

504.11.1 Vent locations. Attic ventilation openings shall not be located in soffits, in eave overhangs, between rafters at eaves, or in other overhang areas. Gable end and dormer vents shall be located not less than 10 feet (3048 mm) from lot lines. Underfloor ventilation openings shall be located as close to grade as practical.

504.12 Detached accessory structures. Detached accessory structures located less than 50 feet (15,240 mm) from a building containing habitable space shall have exterior walls constructed with materials approved for not less than 1-hour fire-resistance-rated construction, heavy timber, log wall construction, or constructed with approved noncombustible materials or fire-retardant-treated wood on the exterior side. The fire-retardant-treated wood shall be labeled for exterior use and meet the requirements of Section 2303.2 of the International Building Code.

504.12.1 Underfloor areas. Where the detached structure is located and constructed so that the structure or any portion thereof projects over a descending slope surface greater than 10 percent, the area below the structure shall have underfloor areas enclosed to within 6 inches (152 mm) of the ground, with exterior wall construction in accordance with Section 504.5 or underfloor protection in accordance with Section 504.6.

EXCEPTION:

The enclosure shall not be required where the underside of exposed floors and exposed structural columns, beams and supporting walls are protected as required for exterior 1-hour fire-resistance-rated construction or heavy timber construction or fire-retardant-treated wood on the exterior side. The fire-retardant-treated wood shall be labeled for exterior use and meet the requirements of Section 2303.2 of the International Building Code.

505 Class 2 ignition-resistant construction.

505.7 Appendages and projections.Accessory structures attached to buildings with habitable spaces and projections, other than decks, porches, balconies, or stairs, shall be not less than 1-hour fire-resistance-rated construction, heavy timber construction or constructed of one of the following:

1. Approved noncombustible materials.

2. Fire-retardant-treated wood identified for exterior use and meeting the requirements of Section 2303.2 of the International Building Code.

3. Ignition-resistant building materials in accordance with Section 503.2.

EXCEPTION:

Not adopted.

505.8 Decks and appendages. The material of decks, porches, balconies, and stairs shall be constructed with any of the following materials:

1. Ignition-resistant material that complies with the minimum performance requirement of Section 503.2.

2. Exterior fire-retardant-treated wood.

3. Noncombustible material.

4. Any material that complies with the minimum performance requirements of Section 503.2 when attached exterior wall covering is also either noncombustible or ignition-resistant material.

5. Heavy timber construction consisting of the following:

5.1. Posts shall be a minimum of 6 inches x 6 inches nominal dimension.

5.2. Beams shall be a minimum of 6 inches x 8 inches nominal dimension.

5.3. Joists shall be a minimum of 4 inches x 8 inches nominal dimension spaced at no greater than 24 inches on center.

505.8.1 Clearance. Decks with less than 48 inches of clearance from finished grade to deck joists shall be enclosed with screen material with openings no greater than 1/4-inch maximum to prevent accumulation of combustibles and to prevent embers from coming in underneath.

505.8.2 Walking surfaces. The walking surface material of decks, porches, balconies, and stairs shall be constructed with one of the following materials:

1. Ignition-resistant material that complies with the performance requirements of Section 503.2.

2. Exterior fire-retardant-treated wood.

3. Noncombustible material.

4. Where the deck, porch, balcony, or stairs are constructed of heavy timber in accordance with Section 501.6, natural wood decking products shall be:

4.1. 2-inch nominal dimension lumber; or

4.2. 5/4-inch nominal hardwood (i.e., teak, mahogany, or other approved hardwood).

5. Material that complies with the performance requirements of Section 505.8.2.1 when tested in accordance with ASTM E2632 and when attached exterior wall covering is also composed of only noncombustible or ignition-resistant materials.

EXCEPTION:

505.8.2.1 Material in Section 505.8.2, Item 5. The walking surface material shall be tested in accordance with ASTM E2632 and shall comply with the following condition of acceptance. The ASTM E2632 test shall be conducted on a minimum of three test specimens and the peak heat release rate shall be less than or equal to 25 kW/ft2 (269 kW/m2). If any one of the three tests does not meet the conditions of acceptance, three additional tests shall be run. All the additional tests shall meet the condition of acceptance.

505.9 Exterior glazing. Exterior windows, window walls and glazed doors, windows within exterior doors, and skylights shall be tempered glass, multilayered glazed panels, glass block or have a fire protection rating of not less than 20 minutes.

505.10 Exterior doors. Exterior doors shall be approved noncombustible construction, solid core wood not less than 1 3/4 inches thick (45 mm), or have a fire protection rating of not less than 20 minutes. Windows within doors and glazed doors shall be in accordance with Section 505.8.

EXCEPTION:

Vehicle access doors.

505.11 Vents. Attic ventilation openings, foundation or underfloor vents or other ventilation openings in vertical exterior walls and vents through roofs shall not exceed 144 square inches (0.0929 m2) each. Such vents shall be covered with noncombustible corrosion-resistant mesh with openings not to exceed 1/4 inch (6.4 mm) or shall be designed and approved to prevent flame or ember penetration into the structure.

505.11.1 Vent locations. Attic ventilation openings shall not be located in soffits, in eave overhangs, between rafters at eaves, or in other overhang areas. Gable end and dormer vents shall be located not less than 10 feet (3048 mm) from lot lines. Underfloor ventilation openings shall be located as close to grade as practical.

505.12 Detached accessory structures. Detached accessory structures located less than 50 feet (15,240 mm) from a building containing habitable space shall have exterior walls constructed with materials approved for not less than 1-hour fire-resistance-rated construction, heavy timber, log wall construction, or constructed with approved noncombustible materials or fire-retardant-treated wood on the exterior side. The fire-retardant-treated wood shall be labeled for exterior use and meet the requirements of Section 2303.2 of the International Building Code.

505.12.1 Underfloor areas. Where the detached accessory structure is located and constructed so that the structure or any portion thereof projects over a descending slope surface greater than 10 percent, the area below the structure shall have underfloor areas enclosed to within 6 inches (152 mm) of the ground, with exterior wall construction in accordance with Section 505.5 or underfloor protection in accordance with Section 505.6.

EXCEPTION:

The enclosure shall not be required where the underside of exposed floors and exposed structural columns, beams and supporting walls are protected as required for exterior 1-hour fire-resistance-rated construction or heavy-timber construction or fire-retardant-treated wood on the exterior side. The fire-retardant-treated wood shall be labeled for exterior use and meet the requirements of Section 2303.2 of the International Building Code.

507 Replacement or repair of roof coverings.

507.1 General. The roof covering on buildings or structures in existence prior to the adoption of this code that are replaced or have 50 percent or more replaced in a 12-month period shall be replaced with a roof covering required by Section 501.4 or based on the type of ignition-resistant construction as determined by Section 501.1 Exception 1.

[Statutory Authority: RCW 19.27.031 and 19.27.074. WSR 23-23-107, § 51-55-0500, filed 11/15/23, effective 3/16/24. Statutory Authority: RCW 19.27.031, 19.27.074, and 19.27.560. WSR 23-02-056, 23-12-109, and 23-20-028, § 51-55-0500, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24.]

PDF51-55-0600

Fire protection requirements.

602 Automatic sprinkler systems.

602.1 General. An approved automatic sprinkler system shall be installed when required by the authority having jurisdiction.

[Statutory Authority: RCW 19.27.031, 19.27.074, and 19.27.560. WSR 23-02-056, 23-12-109, and 23-20-028, § 51-55-0600, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24.]

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Chapter 7—Vegetation management plan.

User note:About this chapter: The purpose of this chapter is to provide criteria for submitting vegetation management plans, specifying their content and establishing a criterion for considering vegetation management as being a fuel modification.

701 General.

701.1 Scope. Vegetation management plans shall be submitted to the code official where required for review and approval as part of the plans required for a permit.

701.2 Plan content. Vegetation management plans shall describe all actions that will be taken to prevent a fire from being carried toward or away from the building. A vegetation management plan shall include the following information:

1. A copy of the site plan.

2. Methods and timetables for controlling, changing or modifying areas on the property. Elements of the plan shall include removal of slash, snags, vegetation that may grow into overhead electrical lines, other ground fuels, ladder fuels and dead trees, and the thinning of live trees.

3. A plan for maintaining the proposed fuel-reduction measures.

701.3 Fuel and 6/7/23 modification. To be considered a fuel modification for purposes of this code, continuous maintenance of the clearance is required.

[Statutory Authority: RCW 19.27.031, 19.27.074, and 19.27.560. WSR 23-02-056, 23-12-109, and 23-20-028, § 51-55-0700, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24.]

PDF51-55-0800

Chapter 8—Fire hazard severity form.

User note:About this chapter: The purpose of this chapter is to provide an alternative methodology to using Table 502.1 for analyzing the fire hazard severity of building sites using a preassigned value/scoring system for each feature that impacts the hazard level of a building site. Included in the evaluation are site access, types and management of vegetation, percentage of defensible space on the site, site topography, class of roofing and other construction materials used on the building (existing or to be constructed on the site), fire protection water supply, and whether utilities are installed above or below ground.

801 Fire hazard severity form. Where adopted, Table 801.1 is permitted to be used as an alternative to Table 502.1 for analyzing the fire hazard severity of building sites.

TABLE 801.1

FIRE HAZARD SEVERITY FORM

(No change to the table)

[Statutory Authority: RCW 19.27.031, 19.27.074, and 19.27.560. WSR 23-02-056, 23-12-109, and 23-20-028, § 51-55-0800, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24.]

PDF51-55-0900

Chapter 9—Fire danger rating system.

User note:About this chapter: The fuel models included in Chapter 9 are only general descriptions because they represent all wildfire fuels from Florida to Alaska and from the East Coast to California.

The National Fire Danger Rating System (NFDRS) is a set of computer programs and algorithms that allows land management agencies to estimate today's or tomorrow's fire danger for a given rating area. NFDRS characterizes fire danger by evaluating the approximate upper limit of fire behavior in a fire danger rating area during a 24-hour period based on fuels, topography and weather, or what is commonly called the fire triangle. Fire danger ratings are guides for initiating presuppression activities and selecting the appropriate level of initial response to a reported wildfire in lieu of detailed, site- and time-specific information.

Predicting the potential behavior and effects of wildland fire are essential tasks in fire management. Surface fire behavior and fire effects models and prediction systems are driven in part by fuelbed inputs such as load, bulk density, fuel particle size, heat content and moisture content. To facilitate use in models and systems, fuelbed inputs have been formulated into fuel models. A fuel model is a set of fuelbed inputs needed by a particular fire behavior or fire effects model. Different kinds of fuel models are used in fire spread models in a variety of fire behavior modeling systems. The fuel models in this appendix correlate with the light, medium, and heavy fuel definitions found in Chapter 2 of the code.

901 Fuel models.

901.1 General. The Fuel Model Key is provided in Table 901.1. Fuel Models are described in Sections 901.1.1 through 901.1.20.

TABLE 901.1

FUEL MODEL KEY

(No change to the table)

901.1.1 FUEL MODEL A. (No change to the text)

901.1.2 FUEL MODEL B. (No change to the text)

901.1.3 FUEL MODEL C. (No change to the text)

901.1.4 FUEL MODEL D. (No change to the text)

901.1.5 FUEL MODEL E. (No change to the text)

901.1.6 FUEL MODEL F. (No change to the text)

901.1.7 FUEL MODEL G. (No change to the text)

901.1.8 FUEL MODEL H. (No change to the text)

901.1.9 FUEL MODEL I. (No change to the text)

901.1.10 FUEL MODEL J. (No change to the text)

901.1.11 FUEL MODEL K. (No change to the text)

901.1.12 FUEL MODEL L. (No change to the text)

901.1.13 FUEL MODEL N. (No change to the text)

901.1.14 FUEL MODEL O. (No change to the text)

901.1.15 FUEL MODEL P. (No change to the text)

901.1.16 FUEL MODEL Q. (No change to the text)

901.1.17 FUEL MODEL R. (No change to the text)

901.1.18 FUEL MODEL S. (No change to the text)

901.1.19 FUEL MODEL T. (No change to the text)

901.1.20 FUEL MODEL U. (No change to the text)

[Statutory Authority: RCW 19.27.031, 19.27.074, and 19.27.560. WSR 23-02-056, 23-12-109, and 23-20-028, § 51-55-0900, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24.]

PDF51-55-1000

Chapter 10—Referenced standards.

ASTM

E2632-2020: Standard Test Method for Evaluating the Under-Deck Fire Test Response of Deck Materials

501.6

[Statutory Authority: RCW 19.27.031, 19.27.074, and 19.27.560. WSR 23-02-056, 23-12-109, and 23-20-028, § 51-55-1000, filed 1/3/23, 6/7/23, and 9/25/23, effective 3/15/24.]