(1) The outdoor walking and driving areas must be surfaced with concrete, asphalt or gravel or other materials that have been effectively treated to minimize dust, facilitate maintenance, and prevent muddy conditions.

(2) Exterior surfaces of buildings and mobile food units must be of weather-resistant materials and must comply with law.

(3) Outdoor storage areas for refuse, recyclables, or returnables must be of materials specified under WAC 246-215-05505 and 246-215-05510.