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Joist Hangers

Joist hangers are metal fasteners used to support the joist where it connects with the beam or perimeter joist. They serve to insure that the weight of the joist bears properly on the beam. A joist hanger is a piece of sheet metal that is flat on the bottom, to cradle the joist, and twisted on each of its sides so it also sits flat against the beam. The hanger is then nailed to the beam. There are several alternative joist end attachments, but most are less reliable.

Toe nailing is a common way of connecting a joist to a beam. When the joist is toe-nailed, the nail is driven at about a 45-degree angle through the side of the joist end, into the beam. This can be unreliable if done incorrectly because the structural load will not bear properly on the nail, leading to eventual separation of the junction.

Joist hangers address this vulnerability by insuring proper shear loading. Shear load describes the way the structural load bears on the junction. Think of it this way: You can break a pencil easily when you put your thumb in the middle and bend it from each end. Now form a fist over each end of the pencil and push your hands together. Pull straight back with one hand while pushing forward with the other. It’s very hard to break the pencil at the point in between your hands, isn’t it? The pressure that you are putting on the pencil is a shear load.

Contributed by Justin Gore
Quality Assurance Supervisor
US Inspect, LLC