Last Updated:
31-Jul-2009
Trussed Rafter Types
Trussed rafters come in all shapes and sizes, they are specifically designed for each project and as such there is no standard off the shelf truss. Trussed rafters fall into one of three styles:-
- Duo-pitch trusses which have two rafters (slopes) meeting at an apex, this is the most common shape
- Mono-pitch trusses which have only one rafter
- Hip trusses like those used within a hipped roof, they can be pitched on one or both sides with a flat middle or they can be completely flat topped with no slopes
The configuration of a trusses internal webs and the timber sizes used is determined by the span, the pitch, and the loads applied to the truss, such as snow and wind loads, the roof covering loads, water tank loads, hoist loads etc.
These are some of the most common types of trussed rafters manufactured today, there are others, but most are just a variation of one these below. TRA Data Sheet 2 contains two pages of trussed rafter profiles.
King Post- A King Post truss is the simplest form of truss, it consists of two rafters that meet at the apex of the truss, a ceiling tie that ties the two rafters together and one centre web that connects the ceiling tie to the apex. The King Post trusses we manufacture usually span up to 3100mm.
Queen Post- A Queen Post truss is similar to the King Post truss, the only difference being that it has two additional webs connecting the rafters to the centre web at the ceiling tie. The Queen Post trusses we manufacture usually span up to 4800mm.
Fink- The Fink truss is the most common truss used today, it's webs are configured in a W shape with the centre bay most commonly being used to carry a water tank. The Fink trusses we manufacture usually span up to 9000mm.
Howe- The webs in a Howe truss are configured similar to those in the Queen Post, the only difference being that it has an additional vertical web connecting each rafter to the ceiling tie. Howe trusses are usually used as multi-ply girder trusses. The Howe trusses we manufacture usually span between 4000mm to 9000mm.
Fan- The webs in a Fan truss are configured similar to the webs in a Fink truss with the addition of an extra vertical web connecting each rafter to the ceiling tie. The Fan trusses we manufacture usually span up to 11000mm.
Double W- The Double W truss is most commonly used for large spans or to reduce the timber sizes on smaller span trusses in high load situations. The webs are configured in a WW shape with the two W's meeting at the apex. The Double W trusses we manufacture usually span up to 12000mm.
Cantilever- Description coming soon.
Bobtail / Stub End- Description coming soon.
Raised Tie- Description coming soon.
Flat Top (Hip End)- Description coming soon.
Mono 2/1- Description coming soon.
Mono 2/2- Description coming soon.
Mono 3/2- Description coming soon.
Scissor- Description coming soon.
Attic / RiR (Room-in-the-Roof)- Description coming soon.
easi-attic (easi-joist attic)- Description coming soon.
Parallel- Description coming soon.
