Joist Hanger
/ dʒɔɪst ˈhæŋə /
Also known as: timber hanger, beam hanger, joist connector
Definition
A joist hanger is a galvanised pressed-steel bracket that supports a timber joist, trimmer, or beam at its end, connecting it to the face of a supporting wall, beam, or header without the joist needing to sit on top. The joist sits in the hanger's cradle; the hanger is nailed to the supporting member through every nail hole using manufacturer-specified joist hanger nails (not screws, unless rated). Load capacity is only achieved with all holes filled correctly - missing nails or wrong nail type significantly reduces capacity. Available in sizes to match all standard timber sections and in types for standard, heavy-duty, skewed, and top-fix applications. Must be galvanised; checked by Building Control as part of floor construction inspection.
In practice
Joist hangers are the standard connection method when floor joists need to connect to the face of a steel beam (RSJ or flitch beam) - without hangers, the joists would need to sit on top of the beam, raising the floor level by the full joist depth. By using hangers fixed to the beam web or flange, the joist tops can be brought level with the beam top flange, keeping the floor level consistent. This is critical in loft conversions where controlling floor-to-ceiling height is important.
The most common installation error is under-nailing - fitting the hanger but only driving nails into a few of the available holes. The published load capacity on the manufacturer's datasheet assumes all holes are filled. For a 47x195mm joist hanger carrying a heavily loaded floor, the difference between fully nailed and half-nailed can be the difference between a safe and an unsafe connection. Building Control surveyors will check nailing completeness on larger projects; on self-build or extension projects without regular inspections, it is the builder's responsibility to fix correctly.
See also