Wis. Stat. § 167.19: Farm machinery storage.

(1) Retail dealer’s buildings for the storage of farm tractors, trucks and motorized farm machinery may be metal covered, pole type or frame and if other than metal or concrete covered shall not be closer than 30 feet to any other building. If the building is more than 50 feet in length it shall have more than one door.

(2) Motor fuel and storage batteries must be removed from units stored in such buildings, and any repairing or overhauling of the units in such buildings is prohibited.