Section 6-102.11 - Surface Characteristics(A) The outdoor walking and driving areas shall be surfaced with concrete, asphalt, or gravel or other materials that have been effectively treated to minimize dust, facilitate maintenance, and prevent muddy conditions.(B) Exterior surfaces of buildings and MOBILE FOOD ESTABLISHMENTS shall be of weather-resistant materials and shall comply with LAW.(C) Outdoor storage areas for REFUSE, recyclables, or returnables shall be of materials specified under §§ 5-501.11 and 5-501.12.Wis. Admin. Code Department of Health Services § 6-102.11