AITC 110-97
Standard Appearance Grades for Structural Glued Laminated Timber
Industrial Appearance Grade

3.1 Application:
Industrial appearance grade
is ordinarily suitable for construction in industrial plants, warehouses, garages, and for other uses where appearance is not of primary concern.

4.2 Description:
    4.2.1: Laminations may possess the natural growth characteristics of the lumber grade.
    4.2.2: In exposed surfaces, knot holes and other voids measuring over 3/4" shall be filled by the fabricator with a wood-tone colored filler which reasonably blends with the final product or with clear wood inserts. When inserts are used, they shall be selected with reasonable care for similarity of the grain and color of the wood insert to the adjacent wood.
4.2.2.1: For appearance grading purposes, measurement of knot holes and other voids shall be in the direction of the length of the lamination and shall not exceed 3/4" except that a void may be longer than 3/4" if its area does not exceed 1/2 sq. in. Void measurement limitations apply only to the surfaces of the member exposed in the final structure. All characteristics must be considered, however, with respect to their effects on general appearance.
    4.2.3: The wide face of laminations exposed to view shall be free of loose knots. Open knot holes shall be filled. Voids greater than 1/16" wide in edge joints appearing on the wide face of laminations exposed to view shall be filled.
    4.2.4: Exposed faces shall be surfaced smooth. Misses are not permitted.
    4.2.5: The corners of the wide face of laminations exposed to view in the final structure shall be eased. Current industry practice for eased edges is for a radius between 1/8" and 1/2" Other radii for eased edges may be agreed upon between buyer and seller.

Premium Appearance Grade
5.1: Application: Premium appearance grade is the
highest standard appearance grade.

5.2 Description:
    5.2.1: Laminations may possess the natural growth characteristics of the lumber grade.
    5.2.2: In exposed surfaces, knot holes and other voids shall be filled by the fabricator with a wood-tone colored filler which reasonably blends with the final product or with clear wood inserts. When inserts are used, they shall be selected with reasonable care for similarity of the grain and color of the wood to the adjacent wood.
    5.2.3: The wide face of laminations exposed to view shall be selected for appearance and shall be free of loose knots. Voids shall be filled. Knot size shall be limited to 20% of the net face width of the lamination. Not over two maximum size knots or their equivalent shall occur in a 6 ft length. Voids greater than 1/16" wide in edge joints appearing on the wide face of laminations exposed to view shall be filled.
    5.2.4: Exposed faces shall be surfaced smooth. Misses are not permitted.

 

3.2 Description:
    3.2.1: Laminations may possess the natural growth characteristics of the lumber grade.
    3.2.2: Voids appearing on the edge of laminations need not be filled.
    3.2.3: Loose knots and open knot holes in the wide face of laminations exposed to view shall be filled. This restriction does not apply for glued laminated truss members. Edge joints appearing on the wide face of laminations exposed to view need not be filled.
    3.2.4: Members are required to be surfaced on two sides only; appearance requirements apply to these sides. Occasional misses, low laminations or wane (limited to a maximum of 1/4" measured across the width) are permitted on a cumulative basis. The cumulative depth of the misses, low laminations or wane shall not exceed 10% of the width of the member at any glue line. The frequency of occurrence shall not exceed one in 10 pieces of lumber used. The maximum area of low laminations shall not exceed 5% of the surface area of a side; and no more than two low laminations shall be adjacent to one another.
    3.2.5: In accordance with provisions in 3.2.4, wane (limited to 1/4" measured across the width) is permitted in all combinations and is not limited in length. Wane permitted in specific laminating combinations up to 1/6" the lumber width on each side is not limited in length. Occasional wane approximately one foot in length and not exceeding the permissible depth of a low lamination shall be permitted in all combinations without regard to the cumulative effects indicated in 3.2.4.

Architectural Appearance Grade
4.1 Application: Architectural appearance grade is ordinarily suitable for construction where appearance is an important requirement. Any voids under 3/4" in diameter shall be filled by other than the fabricator if the final decorative finish so requires.