Walls are constructed of studs that are placed parallel to each other every 16 inches or 24 inches on center, depending on the building. This spacing is necessary to provide the necessary support for the upper floor or roof structure adequately. This spacing must be maintained along the entire length of the wall. Window and door openings require special framing techniques to keep the required spacing while adequately supporting the upper structure or roof.
Jack studs complete a framed window or door opening. A jack stud is cut to fit the vertical measurement of each side of the opening and are secured under the ends of the header next to the king studs. Jack studs can also be used to continue the 16-inch or 24-inch spacing above and below the opening. Jack studs transfer the weight of the roof or upper story to the floor. Without jack studs, the wall will not be properly supported between the upper and lower plates at the opening.
A king stud is a full-length wall stud that is placed on either side of the header and does not necessary fall into line in the regular 16-inch or 24-inch wall stud spacing. The tops and bottoms of the king studs are secured to the top and bottom plate of the wall assembly like a regular wall stud, but the ends of the header are secured to the to the king stud. A king stud is necessary in framing an opening in the wall but does not transfer the entire weight of the roof or upper structure to the floor and foundation.
A header is a horizontal beam that is designed to carry the load of the wall when the normal span of the wall studs is interrupted by a window or door opening. A header is normally constructed two lengths of framing lumber with a plywood spacer in between. This ensures the header assembly is the same width as the framed wall. While the header supports the top of the opening where studs would normally be, the header itself needs a support system in the form of king and jack studs.