(1) In addition to the provisions of RCW 19.27.031, the state building code shall, upon the completion of statewide mapping of wildland urban interface areas consist of the following parts of the 2018 International Wildland Urban Interface Code, published by the International Code Council, Inc., which are hereby adopted by reference:

(a) The following parts of section 504 class 1 ignition-resistant construction:

(i)(A) 504.2 Roof covering – Roofs shall have a roof assembly that complies with class A rating when testing in accordance with American society for testing materials E 108 or underwriters laboratories 790. For roof coverings where the profile allows a space between the roof covering and roof decking, the space at the eave ends shall be fire stopped to preclude entry of flames or embers, or have one layer of seventy-two pound mineral-surfaced, nonperforated camp sheet complying with American society for testing materials D 3909 installed over the combustible decking.

(B) The roof covering on buildings or structures in existence prior to the adoption of the wildland urban interface code under this section that are replaced or have fifty percent or more replaced in a twelve month period shall be replaced with a roof covering required for new construction based on the type of ignition-resistant construction specified in accordance with section 503 of the International Wildland Urban Interface Code.

(C) The roof covering on any addition to a building or structure shall be replaced with a roof covering required for new construction based on the type of ignition-resistant construction specified in accordance with section 503 of the International Wildland Urban Interface Code.

(ii) 504.5 Exterior walls – Exterior walls of buildings or structures shall be constructed with one of the following methods:

(A) Materials approved for not less than one hour fire-resistance rated construction on the exterior side;

(B) Approved noncombustible materials;

(C) Heavy timber or log wall construction;

(D) 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

(E) Ignition-resistant materials on the exterior side.

Such materials shall extend from the top of the foundation to the underside of the roof sheathing.

(iii)(A) 504.7 Appendages and projections – Unenclosed accessory structures attached to buildings with habitable spaces and projections, such as decks, shall not be less than one hour fire-resistance rated construction, heavy timber construction, or constructed of one of the following:

(I) Approved noncombustible materials;

(II) Fire retardant-treated wood identified for exterior use and meeting the requirements of section 2303.2 of the International Building Code; or

(III) Ignition-resistant building materials in accordance with section 503.2 of the International Wildland Urban Interface Code.

(B) Subsection (1)(a)(iii)(A) of this section does not apply to an unenclosed accessory structure attached to buildings with habitable spaces and projections, such as decks, attached to the first floor of a building if the structure is built with building materials at least two inches nominal depth and the area below the unenclosed accessory structure is screened with wire mesh screening to prevent embers from coming in from underneath.

(b) Section 403.2 Driveways – Driveways shall be provided where any portion of an exterior wall of the first story of the building is located more than one hundred fifty feet from a fire apparatus access road. Driveways in excess of three hundred feet in length shall be provided with turnarounds and driveways in excess of five hundred feet in length and less than twenty feet in width shall be provided with turnouts and turnarounds. The county, city, or town will define the requirements for a turnout or turnaround as required in this subsection.

(2) All counties, cities, and towns may adopt the International Wildland Urban Interface Code, published by the International Code Council, Inc., or any portion thereof.

(3) In adopting and maintaining the code enumerated in subsections (1) and (2) of this section, any amendment to the code as adopted under subsections (1) and (2) of this section may not result in an International Wildland Urban Interface Code that is more than the minimum performance standards and requirements contained in the published model code.