Wood joists rarely fasten directly to steel framing members; there's usually a connector or anchorage material between the wood and metal. While building code requirements and your architect's or engineer's specifications are the decisive authority on wood-to-steel connections, there are several options that satisfy the requirements for most projects. Let your project and your construction skill level guide your choice of joist-to-beam connection.
Joist hangers are the most common method of connecting wood joists to steel beams. In some cases, the same types of hangers that connect wood joists to wood beams are suitable for connecting wood joists to steel beams. However, while you nail joist hangers to wood beams, you usually weld them to steel beams.
To determine if mechanical fastening, such as screwing or riveting is acceptable for your project, consult an architect, engineer or your local building authority. Building codes usually require licensed welders to perform structural welds, such as those between a joist hanger and steel beam.
Wood Top Plate
Similar to a foundation wall's sill plate, a face-mounted wood board on top of a steel beam provides a nailing surface for joists or joist hangers. The most common method of mounting a plate to the top flange of a steel I-beam is to drill corresponding sets of holes through the beam and wooden sill plate material. The holes accommodate bolts, which anchor the wood to the beam's top surface.
Joist hangers or joists attach to the wood plate with nails or screws. Because drilling through structural steel beams might compromise the beams' strength, check with a professional or your building department before using this connection method.
A set of angle brackets, or L-brackets, bolted to the top flange of a steel beam form a saddle that surrounds the opposing faces of a solid-sawn wood joist. Angle brackets have bolt holes on both sides. One side's bolt holes allow you to anchor the bracket to the steel beam, and the other side's bolt holes provide a fastening surface for the joist.
This method nearly always consists of a set of two brackets. The joist sits on edge atop the beam, flanked by the brackets.
A ledger is a board that is face mounted to a vertical surface, usually a wall or foundation. Most attached deck and patio cover structure joists connect to walls via ledgers. Builders occasionally anchor wood ledgers to structural steel beams, usually when the beam sits on top of a load-bearing wall and functions as a rim.
Ledgers run parallel to the steel beam. Once fastened to the beam, the ledger forms a wooden surface suitable for toe-nailing joists or installing joist hangers.
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