* C14, used for scaffolding and formwork
* C16 and C24, general construction
* C30, prefab roof trusses and where design requires somewhat stronger joists than C24 can offer. TR26 is also a common trussed rafter strength class in long standing use in the UK.
* C40, usually seen in glulam

Grading rules for African and South American sawn lumber have been developed by ATIBT according to the