EN 635-1: 1995  (confirmed 2014)

Plywood – Classification by surface appearance – General

Part 1 establishes rules for the classification of plywood by its surface appearance.  Five appearance classes are distinguished – E, I, II, III and IV. The classification is made according to the number and extent of certain natural characteristics of wood and the defects that may arise from the manufacturing process.

Natural classification and manufacturing defects used to classify plywood by its appearance

Natural Characteristics Inherent in Wood
Manufacturing Defects
Knots:

PinSound intergrownUnsoundHoles

Non-adhering & partially adhering knots

 

Open joints
Splits & checks Overlaps
Abnormalities due to insect, marine borers & parasitic plants Roughness, other than that due to irregularities in the structure of the wood
Resin pockets, Resin streaks & inbark Blisters
Irregularities in the structure of the wood Hollows, imprints & bumps
Discolouration which is not wood-destroying Sanding through
Fungal decay which is wood-destroying Glue penetration
Other characteristics Foreign particles – metal, mineral
Repairs – patches, shims, synthetic filler
Defects at panel edges – sanding and sanding defects, missing wood
Other defects