Queen post truss

What a queen post truss is

A queen post truss is a type of truss used in Western-style roof frames. Two posts stand on the level tie beam, one on each side, joined at their tops by a horizontal straining beam, and principal rafters run down from the post heads to the ends of the tie beam. The posts hang the tie beam from above and are also called suspension posts; in Japanese the type is also called tsuizuka truss, the paired-post truss.

The related king post truss has a single post at the centre of the tie beam carrying both principal rafters at its head. It is simple and was widely used for modest spans. The queen post truss has no central post and leaves an open space between its two posts, making it suited to wider spans and easier to use for storage in the roof.

Both types share the same principle of tie beam, rafters and posts forming triangles. They differ in the number and position of the posts and in the arrangement of the diagonals that follows.

Reading the records and the building

Records name the type directly. The Kinoene storehouse of the Iinuma family brewery in Chiba is a large sake store 16 bays long and 9 bays deep, gabled with a raised ridge vent, and its roof frame is recorded as a queen post truss. The choice can be read as a way of roofing a nine-bay span without intermediate posts.

For comparison, the No. 3 storehouse of the Kobayashi brewery in Kuriyama, Hokkaido, a two-storey brick building, and platform shelter No. 2 at JR Kotohira Station in Kagawa are both recorded with king post trusses. Spans of about four and a half bays or 5.5 metres with king post trusses, against the nine-bay span of the Kinoene storehouse with a queen post truss, give a sense of how the type was chosen.

Buildings recorded only as having a yōgoya or truss roof frame are often queen post or king post trusses in fact. Articles should give the type only where a record or repair report states it.

On site, look at the middle of the triangles in the roof. A single central post indicates a king post truss; two posts with an open space between them indicate a queen post truss.