Plywood Grading Rules :Part 6 Veneer Grades for Plywood Panels
Veneer in a finished US trademarked plywood panel must conform to one of the six grades listed in the US PS 1-09 standard: N, the highest classification (rarely produced), followed by A, B, C-plugged, C and D.
See veneer grades for Popular APA Plywood Panels.
The requirements given here apply to panels measuring 2440mm (96”) x 1220mm (48”) and are proportionate for other sizes.
APA has produced two easy to follow guides to help match the grade numbers given on a US finished plywood panel with the requirements of EN 635-3.
Detailed guide (below) listing permissible defects – with maximum sizes.
Simplified guide to the US PS 1-09 veneer grading rules and appearance grades in EN 635-3 based on the appearance of the surface veneers. Equivalents cannot be exactly compared as two different sets of grading rules apply.
|Veneer Grade||Description||Permissible defects – maximum sizes|
|Should be smoothly cut and be either 100% heartwood or 100% sapwood, free from knots, knot holes, pitch pockets, open splits, other open characteristics and stain. The veneer must consist of not more than two pieces in 1220 mm (48”) widths and not more than three pieces in wider panels; and be well matched for colour and grain. When panels are sanded no sander skips are permitted.|
|Must be firm, smoothly cut and free from knots, pitch pockets, open splits and other open characteristics. If consisting of more than one piece, they must be well jointed. When panels are sanded, no sander skips are permitted.|
|Open knots/holes||Not allowed|
|Repairs||May be a max of 18 wood parallel to the grain or synthetic|
|Must be solid and free from open characteristics and broken grain, except as permitted e.g. where there are knots or splits.|
|Knots||25.4mm (1”). Must be sound & tight|
|Open characteristics||1.6mm (1/16”)|
|Splits||0.8 mm (1/32”)|
|Repairs||permitted (unlimited) wood or synthetic|
|Sander skips||permitted up to 5% of panel|
|Tight knots||Up to 38.1mm (1-1/2”) no limit|
|Knot/ open holes||25.4mm (1”) max. With an occasional up to 38.1 mm (1-1/2”) across grain|
|Splits||Measured at 203mm (8”) from panel end – not to exceed 12.7mm (1/2”) in width by ½ panel length, or 9.5mm (3/8”) width by any panel length, provided separation at one end no greater than 1.6 mm (1/16”)|
|Repairs||Permitted in wood or synthetic|
|Improved C veneer|
|Open||6.4 mm (1/4”) x 12.7mm (1/2”)|
|Tight knots||Up to 38.1mm (1-1/2 “)|
|Splits||Limited to 3.2mm (1/8”) width|
|Broken grain||Permitted but limited|
|Repairs||Synthetic and wood permitted|
|Touch sanded may be fully sanded|
|Knots||Up to 63.5mm (2-1/2”) width across grain. Occasional tight knot up to76.2mm (3”)|
|Open knots/ holes||Up to 63mm (2-1/2”) width across grain|
|Splits||Measured at 203mm (8”) from panel end, not to exceed 25.4mm (1”) tapering to not more than 1.6mm (1/16”) where running full panel length. Splits on panel faces 6.4mm (1/4”) width where located within 25.4mm (1”) of parallel panel edge.|
|Wane||When not exceeding 203mm (8”) length width of wane may be up to 76.2mm (3”) pending location in panel.|
|D Grade veneers are not permitted in Exterior grade panels|
veneer grading rules and appearance grades in EN 635-3 based on the appearance of the surface veneers.
US PS 1-09 Standard
EN 635-3 (Softwood)
Grades for Plywood Surface Finish
Non-overlaid APA plywood panels come in three levels of surface finish – sanded, touch-sanded and unsanded.
|Factory sanded for applications where smoothness and appearance are important. The face veneer will be B-grade or better.||Panels which are ‘sized’ to uniform thickness by a light surface sanding during manufacture. Sander skips are permissible. Touch sanding is normally applied to panels with a C-Plugged face.||Sheathing grade panels designed for utility applications and left unsanded.|
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