What Is a Joist Hanger and When Is It Required?
A joist hanger is a galvanized steel connector that supports the end of a joist or beam, transferring its load to the supporting member — the standard alternative to resting joists on top of beams or ledger strips. Hangers are required wherever joists frame into the side of a beam or ledger and cannot bear on top, and wherever the design relies on a positive mechanical connection rather than toenails. They are sized for the specific load and joist size.
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How hangers are specified
Manufacturers (Simpson Strong-Tie dominates) publish allowable loads for every hanger model — the engineer selects the hanger whose capacity meets or exceeds the joist reaction, and the drawings call out the exact model number. Using the wrong hanger (or the right hanger with the wrong nails) is a top framing-inspection failure. The specification includes the fastener schedule: hanger nails are shorter and fatter than common nails, and substituting is not allowed.
Installation rules that matter
Fill every nail hole — an empty hole is lost capacity, and inspectors check. The hanger must fit the joist snugly; a hanger that is too wide allows rotation. For engineered lumber (I-joists, LVLs), use hangers rated for the specific product — the flange thicknesses differ from sawn lumber. Top-flange hangers versus face-mount is a structural choice the engineer makes based on the connection demands.
Beyond joists
The connector family extends to beam hangers for heavy girders, post bases and caps, holdowns and tension ties for uplift and lateral loads, and hurricane ties connecting rafters to walls. On any permitted project, the structural drawings include a connector schedule — and the framer's job is to install exactly what is scheduled, with the specified fasteners, in every location. Field substitutions need engineering approval.
The bottom line
Joist hangers provide the engineered connection where joists frame into beams — specified by model number with exact fasteners. Fill every nail hole, match hangers to the lumber type, and never substitute without approval.
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