British frame grade

Requirements on the birch square edge timber

Moisture content: 14 % (+/- 2%)

Cross section: 

Thickness: 24 мм

Width: 24; 35; 45; 70; 95; 120; 145 мм

Length: 1,0; 1,8; 2,1; 2,4; 2,7; 3,0; 3,3; 3,6; 3,9 м

Maximum deviation of dimensions and shape:

for length:  +5 / +10 мм,

for width:  - 0,5/ +0,5 мм,

for thickness: - 0,5/ +0,5 мм

The material shall be trimmed on both ends. The bow shall not exceed 10 mm.

Surface finish:  S4S or S2S. Optionally the side edges can be left rough after sawing in four side planer/moulder. 

Quality of the lumber: 


- any amount of sound, intergrown or partially intergrown knots and knots with fine cracks.

- any amount of black and split knots, but not exceeding 2/3 of the board’s width

The boards with false heartwood on both sides shall not exceed 30% of the total batch volume. 70% of the boards are allowed to have false heartwood on one face.

- cracks on the ends not exceeding 15 mm on both sides.

- minor wane (not exceeding 8 mm)

Not permissible:

wane, exceeding the specified size, mechanical damage more than 1 mm in depth.

- false heartwood, wormholes and other flaws, not affecting mechanical strength of the wood. 

Hit or miss, saw damage, any kind of decay, heartwood, mould, rotten, tobacco and loose knots as well as the knots,  laying across the whole width of the face; face shakes,