Scissor Beam Roof
Continuing on from part 3.
Scissor beam roof. 2 a roof system with a ceiling so the framing is not visible. There is a hierarchy of timber framing at work here with trusses supporting the ridge and purlin beams. 1 a truss with an interrupted tie beam or scissor truss which allow a vaulted ceiling area. Above these components is a rack of common rafters.
A timber frame truss roof with ridge beam purlins and common rafters is a stunning combination that creates visual interest and structural complexity. Scissor trusses are made with double bottom chords that meet in the center of the truss and scissor together crossing over the king post and continuing onto the top chord. 1 a truss with a tie beam. Floor beam span tables of residential structural design we will now look at roof rafter and beam design.
However designing a scissor truss goes beyond the aesthetics we also have to consider the structural engineering. Here we have a wood framed gable roof. The image below shows a cross section of our simple 12 x 13 house from the joist span tables section of this tutorial. Scissor trusses tend to spread a little when they are loaded.
This means the size of the beams based on the woods species the span roof pitch and the job site location. 2 roof framing open to view not hidden by a ceiling.