The design and bracing of trussed rafters – the 1988 Amendment to BS 5268: Part 3

During the early 'sixties trussed rafters were introduced from North America, where they had been widely and successfully used in conjunction with plywood sarking. The omission of such sarking in Britain left trussed rafter roofs without adequate bracing, and by the late 'sixties some problems were beginning to arise. Sometimes the trussed rafters viewed on plan gradually adopted an ‘S’ shape, so that while the roof at the ridge and eaves remained in position, the rest of the roof moved longitudinally in opposite directions on either side of the ridge. In other cases where the strength of the gable walls was inadequate, the ridge line itself moved, with corresponding movement of the walls.