5 Star Hotel dwg file. Classes of Formed Surface Finishes are the following: Class F1 - Used only for concealed work and shall be as-cast surface produced using closely jointed sawn timber boards, planked formwork, plywood, sheet metal or other suitable proven form material. The surface shall be free from voids and honeycombed areas. Class F2 - Irregularities in the surface finish shall be no greater than those obtained from the use of even thickness square edged closely jointed prepared boards arranged horizontally in a uniform pattern, smooth sanded plywood, sheet metal or other suitable suitable form material. Class F3 - Formwork shall be lined with a material that produces a smooth finish of uniform texture and appearance. Class F4 - Same as Class F3 except that internal ties and embedded metal parts will be permitted. Class F5 - Same as class F4 except that the formwork shall be lined with a rubber or plastic material that produces a uniform ribbed appearance. No form ties will be permitted.