Softwoods are the most frequently-used timbers for load bearing. In order to comply with the Building Regulations they must always be strength graded: they are then usually put into a Strength Class. In the UK, softwoods are graded visually, in accordance with BS 4978:2007, or by machine to EN 14081:2005.
C16/C24 timber is pressure treated to protect the wood against rot & machined with eased edges ensuring each length is gauged and of uniform size making the job on site easier. Less splinters and a more precise finish.