Using the correct specification decking joists is really important when building a deck, both in terms of the class of treatment and strength rating of the components. Q-Deck Plus deck joist come in two specifications. C16 strength graded (Note: each joist has printing along the entire length of one of its widest faces) treated to use class 3 (for use out of ground contact) and C24 strength graded treated to use class 4 (for use in ground contact), marketed as multi-purpose. The multi-purpose joists do not have print on the face of the board so are ideal for making other garden structures such as pergolas, benches and even heavy duty decking. All joists are preservative pre-treated with a built in water repellent and come with a 15 year product warranty against fungal decay and wood boring insect attack.