(1) An accessory structure without a complete exterior wall system enclosing the area under the roof or above the floor that is attached to buildings with habitable spaces and projections (e.g., decks), shall be a minimum of one-hour fire-resistance-rated construction, heavy timber construction, or constructed of one of the following:
(a) noncombustible materials;
(b) fire-retardant-treated wood labeled for exterior use; or
(c) ignition-resistant building materials.
(2) When an attached accessory structure is located so that any portion of the structure projects over a descending slope surface greater than ten percent, the area below the structure shall have all underfloor areas enclosed to within six inches of the ground, with exterior wall construction in accordance with ARM 24.321.308.
(3) If a structure is not located in a designated WUI, this rule does not apply.