Types and Grades of Coast Lumber
The tall trees that grow in the coast forest of British Columbia are, to a large extent, self-pruning. As the trees grow in close proximity to each other, many of the lower branches die and are broken off by wind or snow. This results in a straight clean trunk that develops clear wood fiber with each annual ring of growth. Because of these special growing conditions, most of the large coast trees have three distinct growth areas or zones, each of which yields a particular type and quality of lumber product when the log is sawn. This is illustrated in the schematic drawing below.
Schematic Cross – Section/X-Ray View of Typical Coastal log Illustrating Zones of Clear, Factory and Construction Lumber.
The outermost area of the log is generally free of knots and produces Clear grades of lumber. Typically, this lumber is virtually knot free and yields high quality appearance fiber in long lengths.
The middle zone of the log tends to have larger knots, which are well spaced and produces what is known as Factory Lumber. This type of lumber is graded specifically for remanufacturing and is evaluated on the basis of the percentage of clear wood that can be recovered by ripping and cross-cutting to remove the knots. A high percentage of clear fiber can be recovered but with some shorter lengths. These grades are particularly well suited for manufacturing products where some short lengths can be utilized such and windows and doors.
The innermost portion of the log contains knotty wood fiber where the knots are more plentiful but generally smaller in size. This fiber yields the common knotty construction grades of lumber that can be used for structural applications or for products such as knotty siding and paneling.
The following pages summarize the most common lumber grades produced by the sawmilling industry in the coast region of British Columbia. These products are generally available in all of the three major coast species (Hem-Fir, Douglas fir and Western red cedar) and to a lesser degree in the two minor species (Yellow cedar and Sitka spruce).
There are basically three different grades or qualities of Clears. The highest grade is virtually void of any defects. When remanufactured, it will yield a high percentage of full-length clear cuttings. The other grades contain some small defects but of a type that does not impair the product for recovery of appearance quality fiber. Clear grades are described in Table 2 and illustrated on pages 12 and 13.
Table 2. Clear Grades
|Grade||Description and Recommended Use|
|No.2 Clear and Better||This top grade is generally free from defects although some pieces have a limited number of imperfections. Widely used where long length clear cuttings are required such as for paneling and ladders. Also suitable for interior and exterior trim, cabinet work, doors, mouldings and other joinery applications, especially, where a natural finish is required.|
|No.3 Clear||Similar in quality and use to No.2 grade but containing a slightly higher number of imperfection.|
|No.4 Clear||A lower, more economical clear grade which permits more imperfections but is still suitable for high recovery of clear cutting by ripping and cross cutting.|
There are a number of different grades of lumber recovered from the factory zone of the log, all of which are intended for ripping or cross cutting to recover clear fiber. This type of lumber is generally referred to as Flitches (if greater than 2″ in thickness) or Shop (if 2″ or less in thickness). There are also grades intended for specific end uses, the most common of which is Moulding Stock. These grades can be more cost effective than using Clears, particularly for uses that can utilize a higher percentage of short cuttings. Factory grades are described in Table 3 and illustrated on pages 14 to 17.
Table 3. Factory Grades
|Grade||Description and Recommended Use|
(greater than 2″)
|Suitable for high quality joinery and factory work such as solid and louvered doors, shutters, screens, windows, room dividers and furniture.|
|Factory Flitch||Yields a minimum of 80% of total volume in clear wood cutting after ripping and cross cutting to remove defects.|
|Shop Flitch||Yields a minimum of 60% of total volume in clear wood cuttings.|
(2″ or less)
|For use where clear cuttings of various widths and shorter lengths are desired in thicknesses of 2″ or less.|
|No.1 Shop and Better||Yields not less than 50% cuttings which are clear on both faces.|
|No.2 Shop||Yields a minimum of 33-1/3% clear cuttings.|
|Moulding Stock(A)||67% recovery of moulding grade when ripped into 1″ strips.|
|Moulding Stock(B)||50% recovery of moulding grade when ripped into 1″strips.|