This design is in accordance with BS 5268-2:2002 Structural use of timber – Part 2: Code of practice for permissible stress design, materials and workmanship.
Timber to be covered, this calculation is not to be used for timber which is fully exposed to the elements.
The studs are restrained in the plane of panel by sheathing or plasterboard provided and constructed in accordance with recommendations given in BS 5268-6.1.
The limitations on bow in most strength grading rules are inadequate for the selection of material for columns. Particular attention should therefore be paid to the straightness of column, for example, by limiting bow or spring to approximately 1/300 of the length.
The effect of holes need not to be calculated where circular holes with diameters not exceeding 25% of the width of the member are positioned on the neutral axis at between 25% and 40% of the actual length from the end.
These calculations are only applicable for stud walls consisting of four or more studs.