Graphical Construction Glossary >> Roofs and roofing. >> Roof Trusses >> king post truss

King post truss

Also known as a crown post. A roof truss mostly wooden with two principal rafters, a tie beam and a central vertical King post. The simplest of trusses. Mainly used with two angled struts.

King post trusses spanning about 20 - 25 feet. Note the wind braces from the truss to the ridge beam. Early 20Th. century. Part of the former convent, CHIJMES area in Singapore

A variation in the method of bracing a king post. This again say 25 feet span at Chatham Royal Dockyard, UK. Early 19Th century.

The K-Post roof truss has historically been made out of timber in quite large sections and was fairly limited in it's span. It can still be seen today in nail plate trusses and lightweight small span steel trusses.

In a traditionally framed wooden truss of this type, as an example say spanning 20ft the member sizes would be in inches:-

• Tie beam - 4"X8"
• Principal Rafter- 4"X5"
• King Post - 4"X4"
• Strut 4"X4"
• Purlin 4"X7"
• Common Rafter 2"X4"
• Ridge Board 1 1/2"X9"

These sizes are of course generalisations as the pitch, strength grade of the timber all come into the equation.

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