Rafters

are pieces of timber, which, standing by pairs on the transom, wall plate, or raising piece, meet in an angle at the top, and form the roof of a building. It is a rule in building, that no rafters should stand farther than 12 inches from one another: and as to their sizes and scantlings, that principal rafters, from 12 feet 6 inches to 14 feet 6 inches long, be 5 inches broad at the top, and 8 at the bottom, and 6 inches thick: those from 14 feet 6 inches, to 18 feet 6 inches long, to be 9 inches broad at the foot, 7 inches at the top, and 7 inches thick: and those from 18 feet 6 inches, to 21 feet 6 inches, to be 10 inches broad at the foot, 8 at the top, and 8 thick. Single rafters, 8 feet in length, must have 4¹⁄₂ inches, and 3³⁄₄ in their square. Those of 9 feet long, must be 5, and 4 inches square.