Rim Board
A rim board (also called band board or rim joist) is the structural member installed around the perimeter of a floor frame, standing on edge on top of the wall below and closing off the ends of the floor joists. Rim board transfers vertical and lateral loads between floors and provides a nailing surface for exterior sheathing.
In Detail
In I-joist floor systems, rim board is typically made from LVL or LSL and must match the depth of the I-joists exactly. Using solid lumber as rim board with I-joists is not recommended because dimensional lumber shrinks significantly across the grain, while I-joists do not shrink, leading to differential movement, nail pops, and floor squeaks at the perimeter.
Rim board serves multiple functions: it transfers vertical loads from the wall above to the wall below, transfers lateral (racking) loads from the floor diaphragm to the shear walls, provides fire blocking between floors per code, and serves as a nailing surface for exterior wall sheathing and siding. Because of these combined functions, rim board connections and fastening are specified by the engineer of record.
The most common rim board products are LVL rim board (available in 1-1/4" and 1-3/4" thicknesses) and LSL rim board (available up to 1-1/2" thick). OSB rim board is also available as a lower-cost alternative. Rim board depths match standard I-joist depths: 9-1/2", 11-7/8", 14", 16", and 20".
Related Terms
I-Joist
An I-joist is an engineered wood floor or roof joist shaped like the letter "I" in cross-section, with top and bottom flanges made of solid lumber or LVL connected by a vertical web of OSB or plywood. I-joists are lighter, straighter, and span farther than dimensional lumber joists.
Laminated Veneer Lumber (LVL)
Laminated Veneer Lumber (LVL) is an engineered wood product made by bonding thin wood veneers together with all grain running parallel, creating a beam material that is stronger, straighter, and more dimensionally stable than solid sawn lumber of the same size.
Related Materials
I-Joists (Engineered Wood Joists)
I-joists are engineered wood floor and roof framing members with an I-shaped cross section — LVL or solid lumber flanges bonded to an OSB or plywood web. They are the dominant floor framing material in new residential construction, offering long spans, dimensional stability, and lightweight handling.
LVL (Laminated Veneer Lumber)
Laminated veneer lumber (LVL) is a high-strength engineered wood product made from thin wood veneers bonded with structural adhesive under heat and pressure. It is the most commonly specified engineered beam and header material in residential and light commercial construction.
LSL (Laminated Strand Lumber)
Laminated strand lumber (LSL) is an engineered wood product made from flaked wood strands aligned and bonded with structural adhesive. Known commercially as TimberStrand LSL (Weyerhaeuser), it is used for headers, rim board, studs, and plates where dimensional stability and long lengths are valuable.