BS 5268-7.1:1989 recommends a calculation basis for the permissible clear span for simply supported domestic floor joists of solid timber. The recommendations apply to joists at a maximum spacing of 610 mm centre-to-centre, this being the maximum spacing for which the “load-sharing” assumption may be adopted as described in BS 5268-2. The method of calculation makes no allowance for any contribution of the flooring to the load resistance of the joists where such action can be provided by adequate attachments between the elements as in a stressed skin panel floor. Only uniform loading is considered and concentrated or line loads applied by partitions, trimmers and other similar causes are excluded.
BS 5268-7.1:1989 is applicable to the species and grades of timber given in BS 5268-2.