A joint (8, 6, 7A, 7C, 8A, 8B, 11A, 9A, 9B, 9C) for connection of mutually adjacent structural members (11A, 11B), (11, 12), (12, 14), (11, 13), (11, 11), (11, 12), characterized in that each structural member has a pair of opposed walls (18, 19, 20, 21), (24, 24, 22A, 22A), (50, 51, 52A, 52A), (50, 51, 52C, 52C), (99, 100, 24, 24), (99, 102, 24, 24), (102, 102, 24, 24) whereby in formation of said joint (8, 6, 7A, 7C, 8A, 8B, 11A, 9A, 9B, 9C) each opposed wall (18, 19), (24, 24), (50, 51), (99, 100), (99, 102), (102, 102) of one structural member (11A, 11, 12) is located adjacent to a proximal opposed wall (20, 21), (22A, 22A), (24, 24) of another structural member (11B, 12, 14, 13, 11) and connected thereto by fasteners (26, 17A, 17B).