One of the most fundamental elements of floor design is deciding what size joists are needed to make the floor structurally sound. Unlike suspended timber ground floors, the joists of upper floors have to

be of a much larger section because the spans cannot be broken by means of such things as sleeper walls. The size of roof joists and the grade of timber required can be obtained from ‘Span tables for solid timber members in floor, ceilings and roofs for dwellings’ from TRADA Technology.