Strength of Wood Beams
British hardwoods and large softwood beams cannot have the quality assurance that is available for manufactured members or for graded softwood joists. Because of this there will need to be considerations when designing hardwood structures. Various modification factors have to be used when calculating designs in timber to take into account moisture content, duration of the load, spacing etc.
A lot can be learnt about timber by having it professionally graded to give an idea of its properties. The timber can also be load tested to check that it is of suitable stiffness, and by measuring its moisture content the amount of shrinkage that will occur after installation can be estimated. Much of this guidance will therefore be given to both suppliers and purchasers.
The timber will also be susceptible to shrinkage and decay and infestation, if used or stored inappropriately. The storage will have to be checked regularly and the appropriate species of timber selected for the project.
Problems with timber: the pictures above show a piece of wood that has come apart from the frame.