Ceiling system employs a suspended ceiling in several possible configurations. For light structures an interlocking insulated roof deck panel may be employed with no additional roof joists or ceiling framework. See section on Roofs for details. For structures using Light 100mm Primary framing, 1x2 roof/floor deck joists are used alone or with 1x1 spacers to support the ceiling panels. Basic ceiling system for use with the heavier Primary framing employs a 1024mm on center grid of bay-length 50mm 1x1 beams combined with 1000mm long 1x1 spacers. This is suspended from roof joists or above floor deck by short 1x1 vertical posts or threaded rods with T-nuts.