Lumber Grading and Selection

As you select the raw lumber for your project, you need to be aware that it is available in a variety of grades. The grade is based upon the type, location and number of defects found in a board that are seen to reduce the strength, usefulness or durability of the lumber. Some of the more common visual features that affect the grade are the presence of stains, check, knots and pitch pockets. Although natural features they affect the price and utility of the board. Some grades are virtually free of imperfections, while other grades may contain many knots or other defects. Grading allows us to have some control over the quality of lumber that goes into the project, and in many cases save a little money by using a lesser grade and strategically removing the defects to leave cuttings that will still function well as part of your project.

Grading is done at the sawmill and follows standards set usually by lumber or wood product manufacturing organizations. Hardwoods and softwoods are graded according to different rules. Hardwood is graded in three categories: dimension parts, finished market products and factory lumber. Dimension parts are partly to completely machined pieces meant to be used as delivered. Examples are laminated panels and furniture component squares. Finished market products are meant to be used as is, without further processing, like hardwood flooring, stair risers and treads, and siding. Woodworkers generally need to concern themselves with the third, factory lumber, which is sold rough cut and meant to be resized and milled.

To grade factory lumber the grader decides how many clear cuttings of a minimum size, that are sound on the reverse side, can be taken out of a piece of lumber. Generally speaking, the larger, fewer, and clearer the cuttings are, the better the grade. But it isn’t a simple process. There are many exceptions and guidelines to be considered. Standard lengths for grading hardwoods start at four and go to sixteen feet in increments of one foot. Hardwoods are manufactured to random widths but there are minimum widths for each grade. Here is a hardwood grading chart I came up with to help clarify the differences between grades.

Softwood lumber is classified for use by species, grade and form of manufacture. It too is broken up into three categories: yard lumber, structural lumber and factory and shop lumber. Yard lumber is used for non-framing purposes as it is not stress graded. Structural lumber, what we commonly refer to as dimension lumber, is stress graded and is used for joists, studs, rafters and other house framing applications. Factory and shop lumber is used for general woodworking. Again, size and clarity of the cutting influence the grade. The best to use is called industrial clears and is available in B&BTR (B and Better), C and D grades. All grades are graded on the face side, unlike hardwoods, and B&BTR will get you clear, straight grained stock. If you prefer the knottier look you can go with lower grade. Regionally you may find variations such as ladder and pole stock, stave stock, or pencil stock depending on the needs of local industry.