Hammer Truss: Wednesday’s Word Of The Week
Although it contains the word “truss”, a Hammer Truss roof framing system looks a bit like a truss but acts like an arch. It is typically selected more for its aesthetic value than for structural efficiency, and harkens back to timber roof framing from the Middle Ages.
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| Hammer truss in plant |
A hammer truss has a straight top chord, with a fairly steep roof angle, a curved bottom chord, and series of webs most of which are vertical or horizontal. The bottom chord frequently has two curves, one launching from the other.
Although the members form a series of triangles, the top and bottom chord pinch together away from the ends, so it can’t act like a beam spanning between supports. Instead, a hammer truss relies on the supporting structure resisting thrust, like an arch.
One can create a similar visual appearance and eliminate the support thrust by replacing part of the bottom chord with a steel tie rod.
*Each Wednesday our structural engineer, Rik Vandermeulen, discusses a new term associated with glulam manufacturing. He will do this until we run out of words. If there is a timber or glulam term that you have heard of and want to know more about, let us know in the comments.