No building permit shall be issued until the construction or alteration of a building or structure as proposed shall comply in all respects with the provisions of this bylaw or with a decision rendered by the Zoning Board of Appeals. Any application for such a permit shall be accompanied by a plan, at a scale of not less than one inch equals 40 feet, accurately drawn, showing the actual shape and dimensions of the lot to be built upon, the exact location and size of all buildings or structures already on the lot, the location of new buildings to be constructed, together with the lines within which all buildings and structures are to be erected, the existing and intended use of each building or structure and such other information as may be necessary to provide for the execution and enforcement of this bylaw. A building permit shall be valid for 12 months; however, a twelve-month extension may be granted upon application prior to the expiration of the original permit. If construction or operations have not begun within six months, or if construction is not carried toward completion in as continuous and expeditious a manner as reasonable, the permit shall expire.