The following regulations apply to all districts and all other provisions of this chapter:

   1.   Restrictions on Use. Unless otherwise specified, no use shall be permitted in any district which is prohibited in any less restricted district.

   2.   Residences to the Rear of Principal Building Prohibited. No building to the rear of the principal building on the same interior lot shall be used for residential purposes.

   3.   Required Areas May Not Be Reduced. No lot shall be so reduced in area that any required yard, court, or other open space will be smaller than is prescribed in this chapter for the district in which it is located.

   4.   Subdivision Required. Not more than two dwellings are permitted on any lot, tract or parcel of land until it has been subdivided in accordance with the provisions of Chapter 354 of the Code of Iowa.

   5.   Yard and Area Requirements. No yard or other open space provided about any building for the purpose of complying with the provisions of this chapter shall be considered as providing a yard or open space for any other building, nor shall the lot area per family be reduced in any manner except in conformity with the area regulations herein established for the district in which such building is located.

   6.   Method of Yard Measurement. The setback for front, rear and side yards shall be in all cases measured at right angles from the lot line.

   7.   Building Classifications. Any portion of a building which is covered by a roof shall be considered as part of the building.

   8.   Frontage on Corner Lots. The owner of a corner lot may elect to front the principal building on such lot on either of the two streets upon which the corner lot abuts, and shall maintain building setback the side abutting any street of 30 feet or in line with the majority of existing main buildings (excluding accessory buildings) on the same block.

   9.   Visibility at Intersections. Nothing shall be erected, placed, planted or allowed to grow which will impede vision between a height of 2½ feet and 10 feet above the street in the area bounded by the street right-of-way line and a line joining points 30 feet from the right-of-way line intersection.

   10.   Fences, Walls and Hedges. No fence, wall or hedge over 4 feet in height will be permitted along the front of any residential lot or sides of front yards.

   11.   Signs. The only signs that may be erected or placed on a residential lot or building shall be one sign not exceeding 25 square feet in area advertising only the sale or lease of the premises or one unlighted sign not exceeding one square foot in area, attached flat to the building, pertaining to a home occupation. Also, outdoor bulletin boards for churches and schools are permitted.

   12.   Accessory Buildings. No accessory building or portion thereof or other structure shall be permitted in front yards as herein defined.