Wood. It’s one of the single most common materials we use for home improvement projects, from rough framing to fine finish work. Take one glance through a well-stocked lumberyard and you’ll quickly see that there is a huge variety of different woods available, with an equally huge collection of terminology. So to simplify things a little for your next project, here — in alphabetical order — is a basic look at some of the things you might want to know about wood.
Board-Foot (BF): A standard measurement of lumber, equal to a piece of wood that is 12 inches wide, 12 inches long and 1 inch thick. To convert the size of any piece of lumber into board feet, use the following formula: Width (in inches) x Thickness (in inches) x Length (in feet) divided by 12. For example, a board that is 10 inches wide, 2 inches thick and 14 feet long would contain 23.33 board feet (10 x 2 x 14 / 12).
Clear: Wood that is free of knots, pitch pockets and other defects. This is typically the most expensive grade of wood.
Dimensional Lumber: This is the standard, pre-dimensioned wood used primarily in framing. It is milled to set sizes, such as 2×4, 4×6, etc., which is where the name is derived from.
Engineered Wood: This refers to a wide variety of sheets, boards and trim, made up from smaller pieces of wood that are bonded together using various combinations of adhesive, heat and pressure. Laminated beams, plywood and particleboard sheets, and composite siding and trim boards are all examples of engineered wood.
Hardwood and Softwood: The terms "hardwood" and "softwood" can be a little confusing, in that they have no real bearing on how hard or soft the wood actually is. Hardwoods come from broad-leafed, deciduous trees (trees that lose their leaves seasonally), while softwoods come from needle-bearing conifer trees (trees with cones).
Knotty: Any of a variety of wood species that have a number of decorative knots, typically used as paneling, trim and for making cabinets.
Millwork: A generic term that refers to trim, flooring, doors, windows, and other finished wood pieces and products.
MDF: The acronym for "medium density fiberboard." This is a very common and popular engineered wood material, made from softwood fibers blended with resin and wax and bonded together using heat and high pressure. The resulting material is heavier and denser than particleboard, and is made into boards, sheets and trim.
Moisture Content (MC): Water is a big part of any tree, and when the tree is cut for lumber, some of that moisture needs to be removed prior to use. Lumber can be dried by stacking it in the open air with small spacers between the pieces, which is called air drying or stack drying. It can also be dried in a more controlled manner and to a lower moisture content by placing it in large heated driers, a process called kiln drying (abbreviated KD).
The actual amount of moisture that the finished lumber contains, called the moisture content, greatly affects how and where it should be used. For framing and exterior uses such as fencing and decking, a moisture content of 15-20 percent is common. Wood that is used for interior uses such as trim or paneling should be 12 percent or less, while wood used for cabinets, furniture and flooring should be around 8 percent or less.
OSB: The acronym for "oriented strand board." This is an engineered wood material, made from layers of thin, roughly rectangular flakes or strands of wood. The strands are oriented lengthwise on the outer faces, while the inner layers are oriented perpendicular to the outer layers, similar to how the veneers are oriented in making plywood. The stands are bonded together with wax and resin under heat and pressure to form large mats, which are then cut into sheets or strips.
Sheet Goods: Wood that has been made up into sheets, either by laminating thin veneers together (plywood and paneling) or by gluing and pressing wood strips (OSB) or wood particles (particleboard, MDF) into standard size sheets. The most common sheet size is 4 feet by 8 feet in several different thicknesses.
Tight-Knot: A designation for any wood that contains knots that are fully encased in the wood and will not fall out as the wood dries. Tight-knot cedar, for example, is less expensive than clear cedar and is a popular alternative for decking and other exterior uses.
Veneered Wood: Since many types of woods used for millwork and cabinet making can be quite expensive, very thin sheets of the finish-grade wood — called veneers — are often laminated over lesser expensive woods such as pine or composites such as particleboard or MDF. Veneered lumber, trim, and sheets are all commonly available in a variety of wood species.
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