Building Construction Handbook, Eighth Edition

Grading ~ either visually or by computerised machine. Individual

rectangular timber sections are assessed against permissible defect

limitations and grade marked accordingly.

UK grading standard ~ BS 4978.

European grading standard ~ BS EN 14081 (4 parts).

The two principal grades apart from rejects are, GS (general structural)

and SS (special structural) preceded with an M if graded by machine.

Additional specification is to BS EN 338: Structural timber.

Strength classes. This standard provides softwood strength

classifications from C14 to C40 as well as a separate classification

of hardwoods.

A guide to softwood grades with strength classes for timber from

the UK, Europe and North America ~

Source/species Strength class (BS EN 338)

C14 C16 C18 C22 C24 C27 C30

UK:

British pine GS SS

British spruce GS SS

Douglas Fir GS SS

Larch GS SS

Ireland:

Sitka and Norway

spruce

GS SS

Europe:

Redwood or white-

wood

GS SS

USA:

Western whitewood GS SS

Southern pine GS SS

USA/Canada:

Spruce/pine/fir or

hemlock

GS SS

Douglas fir and larch GS SS

Canada:

Western red cedar GS SS

Sitka spruce GS SS

Materials Testing---Softwood Timber Classification