In order to secure minimum basic provision for light, air, privacy and safety from fire hazards, it is required that every building hereafter constructed shall be upon a building site of dimensions such as to provide for the yards specified for the district in which the lot is located, and the following sections shall apply and control. Every such yard shall be open and unobstructed from the ground upward, except as otherwise provided for accessory buildings in Sections 17.52.270, 17.52.310 and 17.52.320, for fences in Section 17.52.410 and for other buildings in Section 17.52.370 and for signs as regulated by Section 17.52.520 and Section 17.52.470. No mobilehome, recreational vehicle, utility trailer, unmounted camper top or boat shall be stored in the front yard or the required side yard in any R district. (Prior gen. code § 8-60.33)