By grades
Birch plywood regular grades are:
B/BB, BB/BB, BB/CP, CP/CP, CP/C sanded from two sides
C/C unsanded
Special grades and special assembly of plywood are also available.
Detailed grading rules and full quality requirements are described in EN-314
Simplified Russian plywood grading rules in accordance with GOST 10.55-71 and GOST 3916.1-96 are presented below:
| EN 314 | Grade B | Grade BB | Grade CP | Grade C |
|---|---|---|---|---|
| GB/T 9846 | Grade I | Grade II | Grade III | Grade IV |
| Pin knots | Not more than 3 per square meter | Allowed | Allowed | Allowed |
| Sound intergrown knots | Allowed with diameter not more than 15 mm | Allowed with diameter not more than 25 | Allowed with cracks not wider than 1,5 mm | Allowed |
| Other knots | Allowed with maximum diameter 6 mm | Allowed with maximum diameter 6 mm | Allowed with maximum diameter 6 mm | Allowed with maximum diameter 40 mm |
| Closed splits | Maximum length 200 mm | Maximum length 200 mm | Allowed | Allowed |
| Open splits | Not allowed | Allowed with maximum size 200*2 mm | Allowed with maximum size 300*2 mm | Allowed with maximum width 10 mm |
| Light discoloration | Allowed not more than 5% of the surface | Allowed | Allowed | Allowed |
| Heavy discoloration | Not allowed | Not allowed | Not allowed | Allowed |
| Glue penetration (through faces) | Not allowed | Allowed not more than 2% of the surface of the panel | Allowed not more than 5% of the surface of the panel | Allowed |
| Veneer overlapping | Not allowed | Allowed with maximum length 100 mm | Allowed with maximum length 200 mm | Allowed |
| Repairing by plugs | Not allowed | Allowed with single plugs | Allowed with double plugs | Allowed with double plugs |
| Sanding through faces | Not allowed | Not allowed | Not allowed | Allowed |