Brooks Bros guide to Timber Grading
In order to grade timber we need to have quality and quantity rules; in Africa there are many but only one meets the complete criteria and therefore is the one normally used.
This Grade is FAS IMPERIAL.
This particular grading rule originated in England and has been adopted by the ATIBT and is found in all OAB countries (Organisation Africaine des Bois) although in Ghana there is a little variation.
The FAS IMPERIAL system operates within certain requirements as follows: timber must be sawn at a larger dimension that specified in the contract in order to allow shrinkage that will naturally occur as the timber dries. Each pack must be representative of the species and quality offered. The limits are measured at the lower end specification of the pack, thus ensuring all other boards are of a higher quality and therefore meet at least the criteria of the grade. The timber is graded on the worst face of the board. The percentages are always calculated in volume, i.e. m³.
40% free of defects and sap
60% maximum with defects based on the following limits
and with sap not exceeding 10% of the width of the board.
<1.00m² 1 defect
1.00 – 1.50m² 2 defects
>1.50m² 3 defects
1 defect 1 knot 16-32mm diameter.
2 knots <16mm diameter.
A small wormhole.
A small gum pocket not exceeding 32cm² of surface.
A small split on the extremity not exceeding 10% of the board length.
2 defects 1 knot 32-64mm diameter.
A small gum pocket 32-64cm² of surface.
A split as in point 'e)' but not straight.
3 defects 1 knot 64-89mm diameter.
A gum pocket bigger than 64cm² but not exceeding 97cm² .