The importance of consistent grades and accurate measurements cannot be underestimated.
Timberpride uses the standardised European Hardwood Grading System which encompasses visual grading for the load bearing characteristics of structural timber and appearance grading of hardwood timber for non-structural applications.
Oak grades are stipulated by the presence, size and/or frequency of knots and splits on the ‘best face’ of the plank or board. The characteristics of the worst face are taken into account if they are likely to affect the performance of the timber in its intended use.
Grade letters indicate the genus and form of the timber e.g. QB1 where the letters denote the timber and type, and the number denotes the grade
Q = Oak (Quercus is the Latin for the Oak genus)
B = Waney edged boards
F = Square-edged boards
P = Beams
Grade numbers indicate the board quality in terms of defects. The number defines the maximum size and number of defects allowed per linear meter and the ratio of defect size to the width of the board.
Abbreviated Classifications for European Joinery Oak
- Two-thirds of the board is clean, straight and with a regular heart.
- One knot with a maximum diameter of 20mm per two linear metres is acceptable.
- Larger knots and defects are permissible if the volume is reduced and they are isolated on 15% of the board.
- Knots over 5mm with a maximum cumulative diameter of 50mm per linear meter are acceptable.
- Larger knots are acceptable providing they are isolated to 25% of the board and lead to a volume reduction.
- Sloping, twisted or curly grain is permitted.
- Knots with a cumulative diameter of 100mm per linear meter are acceptable.
- Larger and unsound knots are acceptable, providing they are isolated to 25% of the board and lead to a volume reduction.
- Knots over 10mm with a cumulative diameter of 160mm per linear meter are accepted.
- All other defects accepted with a reduction in volume if isolated on 30% of the board.