UK 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:
Permissible:
- 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
- false heartwood, wormholes and other flaws, not affecting mechanical strength of the wood.
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:
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,
wane, exceeding the specified size, mechanical damage more than 1 mm in depth.