Item

A grade

B grade

C grade

D grade

E grade

Grain

Regular straight grain, mountain grain

Regular straight grain, mountain grain, half straight grain

Straight grain, mountain grain,

half straight grain

Straight grain, mountain grain, messy grain

No limited

Live knots

φ≤8mm, 2pcs, color natural

φ≤15mm, 2-5pcs, color natural

φ≤60mm, spitting, color closely

Allowed, width≤ 1/3 width of flooring

Allowed, width≤ 1/3 width of flooring

Dead knots

Not allowed

φ≤5mm, 1-2pcs,

spitting, color closely

φ≤20mm, 1-3pcs, spitting, color closely

φ≤40mm, 2-4pcs, spitting, color closely

φ≤60mm, spitting, color closely

Pin knots

Single spitting, overall color closely

Small, spitting, color closely allowed

Spitting, color closely allowed

Spitting, color closely allowed

Spitting, color closely allowed

Side knots

Not allowed

Not allowed

Allowed no drop, no cracking,

not allowed dead knots

Allowed no drop, no cracking,

not allowed dead knots

Allowed no drop, no cracking,

not allowed dead knots

Holes

Not allowed

φ≤1mm, 3-5pcs, spitting, no color change

φ≤1mm, spitting, not color changed

φ≤1mm, spitting, not color changed

φ≤1mm, spitting, not color changed

Black Lines

Not allowed

Not allowed

1*100mm, 1-3lines, spitting

3*200mm, 3-5lines, spitting

3*200mm, 3-5lines, spitting

Pollution

if the surface can be sanded allowed,

oil not allowed

if the surface can be sanded allowed, oil not allowed

if the surface can be sanded allowed, oil not allowed

if the surface can be sanded allowed,

oil not allowed

if the surface can be sanded allowed, oil not allowed

Splits

Not allowed

Not allowed

3*300mm, 1-2lines,seams not allowed

5*300mm, 1-2lines,seams not allowed

8*600mm, 1-3lines, seams not allowed

End Oxidation

Not allowed

Not allowed

Allowed a slight, but the color closely

Allowed color closely, but the width≤1/4 of flooring width, sq.m≤5%

Allowed color closely, but the width≤1/4 of flooring width, sq.m≤5%

Sub wood

Not allowed

Allowed a slight

Allow only one side, the width≤15% of flooring width

Allow only one side, the width≤20% of flooring width

Allow only one side, the width≤30% of flooring width

color difference

Not allowed

Allowed a slight

Coordination allowed

Coordination allowed

Coordination allowed

Discoloration

Not allowed

Not allowed

Allowed slight natural discoloration, not allowed blue/yellow stained fungus

Allowed slight natural discoloration, not allowed blue/yellow stained fungus

Allowed slight natural discoloration,

not allowed blue/yellow stained fungus

Bark Pocket

Not allowed

Not allowed

2*30mm, 1 line

4*40mm, 3 lines

5*60mm, 3 lines

Watermark,

spacer mark

Not allowed

Not allowed

Not allowed

Not allowed

Not allowed

Decay

Not allowed

Not allowed

Not allowed

Not allowed

Not allowed

Broken grain

Not allowed

Not allowed

Not allowed

Not allowed

Not allowed

Tabby grain

Not allowed

Not allowed

Allowed strip, not allowed flake

Allowed strip, not allowed flake

Allowed strip, not allowed flake

Usually is ABCD Grade, 15-20% AB grade, 80-85% CD grade; If the grade is ABCDE, should have 20% C grade.