C16 and C24 structural timber, what’s the difference?

C16/C24 is the strength grade of the timber, this can be graded visually (BS5268) by a registered qualified grader or by machine. Graders’ evaluate the timbers characteristics, taking into account any knots, fissures or slope of grain etc. to determine its strength class.

Softwoods are graded visually in accordance with BS 5268:2007, or by machine to EN 14081:2005.

C16C16 graded structural timber is the most cost effective option and meets performance requirements. Kiln dried C16 is generally recommended for most applications if the correct spans are used and is mainly used internally for floor and roof joists. Lengths commonly available are 3.0, 3.6, 4.2 and 4.8 meter.

C24C24 graded Premium structural timber is a stronger, more demanding grade and has fewer/smaller knots than C16. C24 is best used where higher loads or wider spans are required. C24 will carry a higher point load than C16 grade.