Chinese grade

Specification for birch square edge timber

Moisture content 10% (+/- 2%)

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)

Length: 2,0 - 4 m with pace 500 mm. The prevailing length is 2 m.

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

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.

Dimensions of a made-up package:1,1 m x 1,1 m x board length

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.