Horizontal members that support the floors in wood frame structures are called JOISTS or BEAMS, depending upon the length of the SPAN (distance between the end supports). Members less than 4 ft apart are called joists; members 4 ft or more apart are called beams. The usual spacing for wood frame floor members is either 16 in. or 24 in. O.C. Joists are usually 2 by 8, 2 by 10, or 2 by 12. A COMMON JOIST is a full-length joist that spans from wall to wall or from wall to girder. A CRIPPLE JOIST is similar to a common joist with the exception that it does not

extend the full span. Cripples are normally interrupted by floor openings.

Girders (fig. 6-16) are horizontal members that support joists at points other than along the outer wall lines. When the span is longer than can be covered by a single joist, a girder must be placed as an intermediate support for joist ends. Ground-floor girders are commonly supported by concrete or masonry pillars and pilasters. A PILLAR is a girder support that is clear of the foundation walls. A PILASTER is set against a foundation wall and supports the end of a girder. Both pillars and pilasters are themselves supported by concrete footings. Upper-floor girders are supported by columns. GIRTS are horizontal wood framing members that help to support the outer-wall ends of upper-floor joists in balloon framing.