Chinese grade
Specification for birch square edge timber
Moisture content 10% (+/- 2%)
Length: 2,0 - 4 m with pace 500 mm. The prevailing length is 2 m.
Length allowance is +2 cm.
Width: 70-200 mm with any pace (the material can be cut with fixed widths 75;100;125;150 mm or other fixed widths)
Thickness: 25 mm. The boards can be cut with 50 mm thickness.
Thickness tolerance: -0+2 mm
Width tolerance: -0+2 mm
Flaws | Grade 1 (AA) | Grade 2 (AB) | Grade 3 (BB) | Grade 4 (BC) | Grade 5 (CC) |
Live knots (knots below 5 mm in diameter are to be disregarded) | Through knots on both faces are permissible 1 knot per 1 linear meter | For better face 1 knot per 1 LM is permissible. For worse face it is not limited unless it may affect the strength of material. | Permissible without limitations. | Permissible without limitations. | Permissible without limitations. |
Black knots (loose, decayed and tobacco ones are not permissible) | Not permissible | Not permissible for the better face. For the worse face black knots are permitted without limitations, excluding loose, decayed and tobacco ones. | The knots are permitted without limitations. | The knots are permitted without limitations. Loose knots are not permitted. | The knots are permitted without limitations. Loose knots are not permitted. |
End cracks | 20 mm long non-through cracks. Through cracks are not permissible. | 40 mm long non-through cracks. 20 mm long through cracks. | 50 mm long non-through cracks. 30 mm long through cracks. | 70 mm long non-through cracks. 50 mm long through cracks. | Any non-through cracks are permitted. 60 mm long through cracks. |
Face shakes | Not permissible | Fine checks up to 20 mm in length are permissible. | Fine checks up to 40 mm in length are permissible. | Fine checks up to 60 mm in length are permissible. | Permissible, if a board integrity is maintained. |
Full-width wane | Not permissible | Not permissible | Not permissible | Not permissible | Permissible at a board end up to 7 cm long |
Half-width wane | Not permissible | Permissible for the worse face; width 5 mm, length 15 cm | Permissible for the worse face; width is 1/3 of a board’s thickness, length 20 cm | Permissible for the worse face; width is 1/2 of a board’s thickness, length 30 cm | Permissible for the worse face; width is 2/3 of a board’s thickness, length 30 cm |
Bow | 1mm per 1 m | 2 mm per 1 m | 7 mm per 1 m | 7 mm per 1 m | Permissible |
Cupping | 2% of face width | 2% of face width | 2% of face width | 2% of face width | Permissible |
Mechanical damage | Not permissible | Broken wood at the wane, torn grain at knots up to 2 mm in depth. | Broken wood at the wane, torn grain at knots up to 2 mm in depth. | Broken wood at the wane, torn grain at knots up to 2 mm in depth. | Permissible |
False heartwood | Not permissible | Not permissible | Random sound heartwood 5x5 cm on the worse face | Sound heartwood is permissible for the worse face with no limitations; for other not permissible | Permissible if without soft rot |
Hard rot | Not permissible | Not permissible | Not permissible | 5% of a board area is permitted | 15% of a board area is permitted |
Soft rot | Not permissible | Not permissible | Not permissible | Not permissible | Not permissible |
Mould | Not permissible | Not permissible | 5% of a board area is permitted | 15% of a board area is permitted | Permissible |
Bluestain | Not permissible | Not permissible | Not permissible | 5% of a board area is permitted | 15% of a board area is permitted |
Packaging
Dimensions of a made-up package:1,1 m x 1,1 m x board length
The boards are stacked into a compact package, each 8-10 rows are separated with a spacer, minimum 10mm and maximum 20 mm in thickness.
PE film is laid under the bottom and top rows.
Five sides of a package are wrapped with film.
Packages are bundled with a PET tape at intervals of 80 cm with the last tape placed on the distance of 20 cm from the end of the package.