WAC 296-150C-0970   Roof construction.  (1) All roofs must be framed and tied into the framework and supporting walls to form an integral part of the commercial coach.

     (2) All trusses must be laterally braced.

     (3) All roof decks must be designed and built with sufficient slope or camber to assure adequate drainage, or must be designed to support maximum loads including possible ponding of water due to deflection.

     (4) Cutting roof framework members for passage of electrical, plumbing, or mechanical systems is prohibited except where substantiated by engineering analysis.

     (5) Electrical, plumbing, or mechanical systems must not penetrate the roofing membrane unless the penetration point is adequately sealed.

     (6) Ventilation. Enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters shall have cross ventilation for each separate space by ventilating openings protected against the entrance of rain and snow. Where eave or cornice vents are installed, insulation shall not block the free flow of air. A minimum of 1 inch of air space shall be provided between the insulation and roof sheathing. The net free ventilating area shall not be less than 1/150 of the space ventilated, except:

     (a) The area may be 1/300, provided 50 percent of the required opening area is provided by ventilators located in the upper portion of the space to be ventilated at least 3 feet above eave or cornice vents; or

     (b) A vapor barrier not exceeding 1 perm is installed on the warm side of the attic insulation.



[Statutory Authority: RCW 43.22.340, 43.22.350, 43.22.355, 43.22.360, 43.22.400, 43.22.432, 43.22.433, 43.22.434, 43.22.450, 43.22.480, and 43.22.485. 00-17-148, § 296-150C-0970, filed 8/22/00, effective 9/30/00. Statutory Authority: RCW 43.22.340,[43.22.]355 , [43.22.]360, [43.22.]432, [43.22.]440 and[43.22.]480 . 96-21-146, § 296-150C-0970, filed 10/23/96, effective 11/25/96.]