A structure, transportable in one or more sections, that, in the travelling mode, is 2. 4 m (8 body-ft) or more in width or 12. 2 m (40 body-ft) or more in length, or, when erected on site, is 29. 7 m2 (320 ft2) or more and that is built on a permanent chassis and designed to be used as a dwelling, with or without a permanent foundation, when connected therein. The term manufacturedhomeincludes any structure that meets all the provisions of this paragraph except the size requirements and with respect to which the manufacturer voluntarily files a certification required by the regulatory agency, and except that such term does not include any self-propelled recreational vehicle. Calculations used to determine the number of square metres (square feet) in a structure are based on the structure's exterior dimensions, measured at the largest horizontal projections when erected on site. These dimensions include all expandable rooms, cabinets, and other projections containing interior space but do not include bay windows.