Commercial lumber is basically any lumber traded in the free market system, bought or sold at either the retail or wholesale level. It comes in many forms, types and species, and is generally graduated into categories of quality to enable users to select the quality best suited for their purposes.
The grading of commercial lumber is based upon the characteristics and features that may lower its strength, durability or appearance. Knots, checks and pitch pockets are some of the visual features that are a natural part of trees. While those grades that make up the vast majority of commercial lumber can contain numerous knots and other features, some grades are essentially free of such features.
Lumber can be divided into two major categories: hardwood and softwood. Hardwood lumber is primarily used for remanufacturing into furniture, flooring, paneling, molding, cabinetry and other millwork. Softwood lumber is primarily used for construction work.
Hardwood lumber can be graduated into the three main categories of factory lumber, dimensioned lumber and finished products.
There are several grades of hardwood factory lumber. The best grade is known as "FAS"; the second-best grade is "FIF"; and the third-best grade is called "Selects". These grades are followed by "No. 1 Common", "No. 2A Common", No. 2B Common "," Sound Wormy "," No. 3A Common "and" No. 3B Common. "Hardwood lumber comes in standard lengths of one foot increments ranging from four feet to sixteen feet in length Standard thicknesses are either either 1/8 inch or 1/2 inch increments ranging from 3/16 inch to 3-3 / 4 thicknesses. Hardwood lumber is manufactured to random widths as the grades do not specify standard widths.
Dimensioned hardwood lumber, also known as "hardwood dimension stock" or "dimension parts", is stock that has been processed into specific lengths, widths and thicknesses and can be either semi-machined or completely machined products. These products are usually kiln-dried and graduated into the three main classes of "hardwood dimension parts", "rough solid kiln-dried squares" and "surfaced solid kiln-dried squares".
Finished hardwood market products are graduated in finished form and generally require no further processing. Examples of finished products include siding, stair treads and risers, trim and molding, construction boards and timbers, and hardwood flooring. Of these hardwood flooring is probably the highest volume product on the market.
Softwood lumber has been used for many years as the primary raw material for use in construction and manufacturing. It is produced in a wide variety of products and from a wide variety of species. Softwood lumber can be classified by its species, grade and form of manufacture, and can be graduated into the three main categories of yard lumber, structural lumber, and factory and shop lumber.
Yard lumber can be further graded into "Select" and "Common" classes. Select lumber is usually not graded according to strength but rather according to appearance, as it is generally intended to receive natural or paint finishes. Common lumber is also not usually graded for stress, is of lower appearance than the Select grade, but is suitable for light construction and utility uses.
Structural lumber is almost always produced in standard dynamic sizes, graded for stress and strength, and assigned allowable structural properties. As the name implies, structural lumber is used as structural members in construction.
Factory and Shop lumber comes in a wide variety of species, sizes and grades of softwood and is typically the raw material for many different secondary manufacturing uses where appearance and finishing characteristics as well as physical properties are important, such as trim molding and cabinet stock.
Various inspection bureaus and grading agencies typically oversee the grading processes at lumber mills, provide re-inspection services and write grading rules for the products and species they represent.
Architects, engineers and construction contractors should be well versed in the types, grades, species and physical properties of commercial lumber. The study of commercial lumber is an excellent topic for the continuing education requirements of these professionals. More information is available from the US Department of Agriculture's Forest Service.