Calculate the rim board material needed for floor perimeters. Estimate lineal feet, sheets, and cost for LVL or OSB rim board.
The rim board (also called a band joist or rim joist) closes off the floor framing at the building perimeter. It sits on top of the sill plate or wall plate and provides a nailing surface for the exterior sheathing, a fire stop between floors, and lateral support for the ends of the floor joists.
Modern construction uses engineered rim board—1.125″ thick LVL or 1″ OSB rim board—instead of solid sawn lumber. Engineered rim board eliminates the differential shrinkage between I-joists and solid lumber band joists that causes drywall cracks, squeaky floors, and nail pops.
This calculator computes the total lineal footage of rim board needed based on the building perimeter, the number of pieces (typically sold in 12', 16', or 20' lengths), and estimated cost. It accounts for waste and any interior bearing walls that also need rim-board closure.
Accurate calculation of this value helps construction professionals plan projects more effectively, reduce material waste, and ensure compliance with building codes and industry standards.
Rim board is a must-have for I-joist floors and is increasingly used with solid lumber joists too. This calculator ensures you order the right quantity for your floor perimeter. This quantitative approach replaces rule-of-thumb estimates with precise calculations, minimizing material waste and reducing the likelihood of costly change orders during construction.
Total LF = Perimeter + Interior bearing walls Pieces = ceil(Total LF × (1 + waste%) / stock length) Cost = Pieces × Stock length × Price per LF
Result: 13 pieces of 16' rim board = $728
Total LF = 160 + 30 = 190 LF. With 5% waste: 200 LF. Pieces = ceil(200/16) = 13 pieces. Cost = 13×16×$3.50 = $728.
Engineered rim board advantages: no shrinkage (dimensionally stable), matches I-joist depth exactly, lightweight and easy to handle, and available in long lengths (up to 20'). Solid lumber rim (2×12): heavier, shrinks 1/8″–3/16″ as it dries, and may not match I-joist depths precisely.
The rim board area is one of the biggest sources of air leakage in a house. Best practice: seal the bottom with sill seal, the top with subfloor adhesive, and the cavity behind with spray foam insulation (R-19 minimum in most climate zones).
Rim board is sold by the piece (each piece is a stock length). Order based on your wall lengths to minimize cuts and waste. Many suppliers stock 12' and 16' lengths; 20' may be special order. Check availability before designing your cut list.
It's not recommended. Solid lumber shrinks as it dries, while I-joists don't. This differential movement causes floor-to-wall separation, drywall cracks, and squeaks. Use engineered rim board for best results.
They're the same thing. "Rim joist" is the traditional term for the solid lumber piece. "Rim board" typically refers to the thinner (1″–1.125″) engineered product designed specifically for this purpose.
Yes, if the floor joists overlap or butt at an interior bearing wall, you need closure material. This can be rim board, solid blocking between joists, or a combination.
LVL rim board is typically 1.125″ thick (standard lumber 1.125″ = 1-1/8″). OSB rim board is 1″ thick. Both are thinner than solid 2× lumber (1.5″), which can be a consideration for siding attachment.
Yes. Rim board transfers vertical loads above the floor to the wall below and provides lateral bracing. LVL rim board has published bearing capacities for point loads. Squash blocks may still be required under heavy concentrated loads.
Divide the total perimeter (plus interior bearing walls) by the stock length, add 5–10% waste, and round up. Typical stock lengths are 12', 16', and 20'.