Roof trusses
Collar beam
A collar beam is a horizontal member that ties a pair of rafters or top chords together part-way up the roof.
Also known as collar beam, collar tie, collar, top tie
Fixed between the two roof slopes above the ceiling, the collar beam stops the rafters from sagging and spreading and forms the ceiling of a room in the roof. It is a key part of frame (A-) trusses and of traditional rafter roofs.
The higher the collar sits, the more headroom there is below it, but the less effective it is at restraining outward spread. Its position is therefore part of the structural design.
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