The provisions of these regulations shall be held to be the minimum requirements adopted for the promotion of public health, safety, convenience and general welfare. When these regulations impose greater restrictions upon the use and development of buildings or land than are imposed or required by any other regulations, permits, restrictions, easements, covenants, or agreements, the provisions of these regulations shall control. Nothing in this section shall require any change of the plans, construction or designated use of a building, the construction or use of which shall have been commenced prior to the effective date of these regulations or of any pertinent amendment thereto, and which shall be completed within one year thereafter.