Queen Post Truss Calculator
A queen post truss uses two vertical posts rising from the bottom chord to the top chords, connected by a horizontal straining beam, giving it more capacity than a king post truss for spans roughly 20-30 ft. This calculator sizes a queen post truss using the same gable-profile geometry.
Size Your Queen Post Truss
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Estimates only. Actual costs vary by region, supplier, and site conditions.
Queen Post vs. King Post Truss
Where a king post truss relies on a single central vertical member, a queen post truss splits that role between two vertical posts positioned symmetrically off-center, connected across the top by a horizontal straining beam. This creates an open central bay historically used to fit a doorway, window, or loft opening directly under the ridge.
The two-post arrangement distributes load more evenly than a single king post, which is why queen post trusses are traditionally used for spans beyond the roughly 16-20 ft range a king post truss handles well, extending comfortably to 24-30 ft in timber-frame and traditional construction.
Like the king post truss, a queen post truss shares the same outer triangular envelope as a standard gable roof, so this calculator uses the gable roof-type option for span, rafter length, and cost — the internal post layout is detailed separately by a truss designer.
Frequently Asked Questions
What is the difference between a king post and queen post truss?
A king post truss has one central vertical post; a queen post truss has two vertical posts set apart, joined by a horizontal straining beam. Queen post trusses typically handle longer spans and leave an open bay under the ridge.
What span is a queen post truss good for?
Queen post trusses are traditionally used for spans of roughly 20-30 ft, longer than the 16-20 ft range typical of a single king post truss, because the two posts share and balance the load.