BS 5268-7.6:1990 recommends a calculation basis for the permissible clear span of purlins used in traditional pitched roof construction, i.e. not including trussed rafter roofs. The method of calculation is for purlins formed from solid timber and supported by external or internal walls or by purlin struts. The major axis of the purlin is perpendicular to the rafter slope; other orientations of the purlin are not covered by this Section of BS 5268. The uniform and concentrated loads of BS 6399-1 are considered. Provision is made for a uniformly distributed snow load derived from BS 6399-3.
BS 5268-7.6:1990 is applicable to the species and grades of timber given in BS 5268-2.