In the framing of a deck or floor system, a rim joist is attached perpendicular to the

joist A joist is a horizontal structural member used in Framing (construction), framing to span an open space, often between Beam (structure), beams that subsequently transfer loads to vertical members. When incorporated into a floor framing system, joi ...

s, and provides lateral support for the ends of the joists while capping off the end of the floor or deck system. Rim joists are not to be confused with end joists, which are the first and last joists at the ends of a row of joists that make up a floor or deck frame. A rim joist's relationship to the joists is similar to what the top or bottom

wall plate A plate or wall plate is a horizontal, structural, load-bearing member in wooden building framing. Timber framing A plate in timber framing is "A piece of Timber upon which some considerable weight is framed...Hence Ground-Plate...Window-plat ...

is to the studs. It is also confusingly called a header ( header also refers to other framing components) or rim board. Collectively, the end joists and rim joists are called band joists, especially in regard to deck construction. In dimensioned lumber construction, the rim joists are the same depth, thickness and material as the joists themselves; in engineered wood construction, the rim joists may be

oriented strand board Oriented strand board (OSB) is a type of engineered wood, formed by adding adhesives and then compressing layers of wood strands (flakes) in specific orientations. It was invented by Armin Elmendorf in California in 1963. OSB may have a rough and ...

(OSB), plywood or an engineered wood material varying in thickness from to as much as , though they are usually

laminated veneer lumber Laminated veneer lumber (LVL) is an engineered wood product that uses multiple layers of thin wood assembled with adhesives. It is typically used for headers, beams, rimboard, and edge-forming material. LVL offers several advantages over typi ...

(LVL) or laminated strand lumber (LSL) thick. In flooring construction, the rim joists sit on the sill plates; in deck construction, they are parallel to the support beams and sit on the beams or in some cases, cantilever away from the beams. A double thickness board in the position of a rim joist is called a flush beam and serves a dual purpose, providing primary support for the joist ends as well as capping the joists.

References

Architectural elements {{architecturalelement-stub