Lumber grading rates wood according to its use. Decide what you can work with and then buy the lowest acceptable grade. If you want a natural finish, buy only top-grade lumber, but if you're going to paint the woodworking project, you can buy a lower grade as the paint will hide the defects. Sutherlands will be glad to help you determine the best buy for your project.
Softwoods and hardwoods are graded differently. Softwoods are graded either by dimension or by board, which is strength and appearance respectively. Your choice will, of course, depend on what your project is. Dimension lumber is mainly used for framing houses, but it can also be used where heavy-duty strength or special thickness is needed. Always get the top of the line when either of these are needed for your project.
In hardwood, the number of defects determine the grade. The best are Firsts, Seconds, and a mix of the two, named FAS. Second best is Select (with defects on the back.) Next is No. 1 and No. 2 Common. There are also sub-grades between FAS and Select. Anything less than what has been mentioned is most likely unusable and not recommended.
Finish - Fine appearance and tight knots.
Premium - Fine appearance and larger knots.
Standard - Typically for Construction use where less finished board is acceptable.
Industrial - Structually sound, but rough grain and frequent knots.
Appearance grade boards generally come from the higher end of standard graded common boards. These boards are mainly for construction purposes and allow larger knots than the finer grades of pine lumber. This grade permits knots up to two-thirds the width of the board depending on the type of knot. It also allows for splits up to twice the width of the board but less than one-sixth its length. Appearance grade lumber often exceeds these requirements.
Stud grade lumber is a general-purpose categorization for lumber that is used in vertical load-bearing capacities. Stud grade lumber is rated from Grades 1 to 5. Stud grade lumber heavily restricts the amount of warp, size and frequency of splits, and holes and knots.