Technical Specifications for Dimensional Lumber

Description of technical specifications for larch dimensional lumber

Manufacturing dimensional lumber from Siberian larch

01

Extra Grade

Complete absence of any defects on the front side (knots, shakes, wane edges, etc.).

Premium Grade

1 defect on the front side is permitted (defect is either a live knot with up to 10 mm in diameter or a resin pocket less than 10-15 mm length and 1-2 mm width).

Free of shakes.

A Grade

1-2 defects per linear meter are permitted (defect is either a live knot with up to 10 mm in diameter or a resin pocket less than 10-15 mm length and 1 mm width).

Free of shakes.

AB Grade

1-3 defects per linear meter are permitted (defect is either a live knot with up to 20 mm in diameter or a resin pocket less than 20-25 mm length and 1 mm width).

Total amount of defects does not exceed 3. Free of shakes.

B Grade

Since all dimensional lumber is made of butt cut, C grade automatically includes all products with defects exceeding the tolerance limits.

An unlimited number of light and dark live knots on the front side is allowed. The maximum diameter is not prescribed. Few shakes up to 1.5 mm width are permitted.

Total length of shakes in the product does not exceed half its length.

Explanation

The given classification is based on the mentioned defects and imperfections on the front side of the product. As for the inner side, any defects and imperfections are allowed. Skip dressing and wane edges are also acceptable if the integrity of the surface does not suffer during installation.