King post trusses
King post truss A roof truss that is mostly wooden with two principal rafters, a tie beam and a central vertical King post.[1] The simplest of trusses. Mainly used with two angled struts.The King post roof truss shown in the gallery was typically restricted to smaller roofs. As an example a roof truss of this type spanning 20 ft would use the following timber sizes.
- Tie beam - 4" × 8"
- Principal rafter- 4" × 5"
- King post - 4" × 4"
- Strut 4" × 4"
- Purlin 4" × 7"
- Common rafter 2" × 4"
- Ridge board 1½" × 9"[2]
Queen post trusses
Queen post truss. A roof truss mostly wooden with two principal rafters and two vertical Queen posts with a restraining tie beam at the bottom and a straining beam at the top.[1]The Queen post truss extends the span and combined with spliced joints in the longer members extends the useful span for trusses of these types. As an example say spanning 35 ft the member sizes would be in inches:-
- Tie beam - 5" × 11", with two pieces spliced.
- Principal rafter- 5" × 7"
- Queen post - 5" × 5"
- Strut 5" × 5"
- Straining beam 5" × 8"
- Straining sill 5" × 3"
- Purlin 4" × 7"
- Common rafter 2" × 4"
- Ridge board 1½" × 9"[2]
Diagrams
These diagrams use terminology commonly used in the UK and Australia.[1] [2]
Section view of a King post roof truss showing the main structural members.
Sketch showing the relationships between the trusses and other roof members
A section through a larger Queen post roof truss
Sketch of trusses
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