A king stud is one of the most important framing members in building construction. These studs support tremendous amounts of weight and pressure from the other framing members in the wood-framed home. Usually placed on both sides of an opening, such as a window or door, the king stud must be solid, free of defects, straight and dry. When choosing the best king studs for your project, inspect the lumber well for these qualities.
Most wood-framed buildings are constructed of yellow or white pine building studs. Pine grows abundantly and is cheap and easy to process. Unfortunately, the wood can retain moisture for long periods of time, and therefore most lumber manufacturers dry their lumber before distribution.
Framing lumber is labeled as air-dried (AD) or kiln-dried (KD). It is best to select KD, since AD lumber retains approximately 15 to 25 percent of its moisture, making it unsuitable as framing lumber. As the moisture in the wood evaporates, the fibers of the wood shrink, causing the stud to twist and warp. Kiln-dried lumber retains only 8 to 10 percent of its moisture, shrinks very little, and is a much better choice for king stud lumber.
Avoid pressure-treated wood. This type of wood is injected with a toxic mixture of preservatives. While this wood is weather-resistant and durable, it is usually very moist and tends to severely warp with time.
Lumber mills also grade their wood by numbers. Number 1 is the highest grade for light structural lumber. The king stud is one of the most important and supportive framing members, so select the Number 1, also labeled as No.1, for best results.
Check the king stud lumber for any defects, knots, bows, twists and crooks. Large knots as well as black or discolored areas imply damage to the tree or damage during manufacturing. Avoid lumber with fungus or mildew, as these spores can reproduce within your wall cavities if introduced to moisture.
To check for twists, bows and crooks, place one end of the king stud on a flat surface. Lift the other end of the stud up toward your eye. Look down the stud and take note of any twists, unevenness or bulges. A little crowning, or bow in the center of the stud, is normal, but avoid severe crowning and other defects. Avoid king stud lumber with cracks or evidences of stresses from manufacturing or drying.
Finally, select a king stud of the correct size. Most studs are mass-manufactured to about 7.719 feet (about 2.35 m) but do come in varying widths. Pay careful attention to the stud sizes you purchase to ensure uniformity and avoid frustrating returns to the home improvement center.