GRADE I depending on surface quality – hardwood

Allowable defects*
Value Description
Pin knots allowable diameter of up to 3 mm; up to 3 pcs/m2
Sound intergrown knots allowable diameter of up to 15 mm (cumulative diameter shall not exceed 30 mm/m2), small cracks allowable
Filled unsound knots and knot holes with diameter of up to 6 mm, up to 2 pcs/m2
Open splits less than 1/10 of a length of a sheet, width up to 3 mm, 3 pcs per sheet width
Closed splits allowable
Wood structure defects minor ones allowable
Sound color changes minor decoloration allowable
Repairs (patches, plugs) 3 pcs/m2 fully filled
Edges defects allowable up to 2 mm

GRADE II depending on surface quality – hardwood

Allowable defects*
Value Description
Pin knots allowable
Sound intergrown knots allowable diameter of up to 35 mm, small cracks
Filled unsound knots and knot holes if not fixed allowable diameter of 5 mm, if fixed – up to 10 mm, 3 pcs/m2
Open splits if properly filled, allowable shorter than 1/5 length of a sheet, width up to 5 mm, 3 pcs/m of a sheet width
Closed splits allowable
Wood structure defects minor allowable
Sound color changes minor decoloration allowable
Repairs (patches, plugs) 6 pcs/m2
Edges defects allowable up to 5 mm
Bark pokets up to width of 5 mm, if correctly filled
Open shakes up to width of 3 mm, 1 pcs/m of sheet width, with splits infilled if their width exceeds 1 mm
Glue seepage small and seldom
Hollows, traces, ridges minor ones allowable
Overlaping up to 1 pcs/m2 and with length up to 100 mm
Surface roughness minor roughness allowable

GRADE III depending on surface quality – hardwood

Allowable defects*
Value Description
Pin knots allowable
Sound intergrown knots up to diameter of 50 mm
Filled unsound knots and knot holes up to diameter of 40 mm
Open splits If not filled allowable: smaller than 1/3 sheet length and with width up 20 mm, 3 pcs/m of sheet length, if filled – no restrictions
Closed splits allowable
Wood structure defects allowable
Sound color changes allowable
Repairs (patches, plugs) no limitations
Edges defects allowable up to 5 mm
Bark pokets up to width of 25 mm
Open shakes up to width of 5 mm, 2 pcs/m of sheet width with splits infilled allowable
Glue seepage allowable up to 5 % of the sheet surface
Oversanding allowable up to1 % of the sheet surface
Hollows, traces, ridges allowable
Overlaping up to 2 pcs/m2
Surface roughness allowable

GRADE IV depending on surface quality – hardwood

Allowable defects*
Value Description
Pin knots allowable
Sound intergrown knots allowable
Filled unsound knots and knot holes allowable
Open splits allowable
Closed splits allowable
Wood structure defects allowable
Sound color changes allowable
Repairs (patches, plugs) no litmiations
Edges defects allowable
Bark pokets allowable
Open shakes allowable
Glue seepage allowable
Oversanding allowable
Hollows, traces, ridges allowable
Overlaping allowable
Surface roughness allowable

* Catalogue of most common defects, for other defects please refer to EN 635 -1-2-3 standards.