Scissors Truss Design
"I think the motto of truss engineers is: If you can dream it, we can build it."
Scissors Truss Design Checklist
- Scissors trusses create interior vaulted ceiling
- Slope is 1/2 pitch of what you see outside
- WATCH truss video below for ideas
- Truss engineers can make anything you want
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What is a Scissor Truss?
A scissor truss is a truss that has sloped bottom chords that create a sloping inverted-V shape inside the room under the truss.
A scissors truss is a really cool roof framing option. You not only get the speed of framing that you get with common trusses but also the added benefits of an interior sloped ceiling.
What is the Normal Interior Slope of the Scissor Truss?
The slope of the interior bottom chord of the scissor truss is one-half the slope of the outer roof.
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For example, if you have a fairly steep 8:12-pitch roof outside, your inside vaulted ceiling pitch will be 4:12.
Those numbers stand for inches of rise per foot of run. In other words, the 8:12 means the roof goes up 8 inches for every horizontal foot it travels.
How Do Engineers Calculate a Scissor Truss?
The companies that fabricate the trusses use sophisticated software to design the trusses. You provide the span of the roof and the desired exterior roof pitch and the software does the rest.
You can ask the structural engineer at the truss fabrication plant if there is a way to increase the interior slope, but I doubt you'll get much more than one-half the slope of the exterior roof surface.
Can you Create a Partial Scissor Truss?
Yes, you can create a partial scissor truss where the bottom chord starts off at a slope but then flattens out before it slopes down to the opposite exterior bearing wall.
I think the motto of truss engineers is: If you can dream it, we can build it.
I say this because I've been to truss manufacturing plants and seen countless drawings for trusses of all different shapes.
A few years ago a new home being built near where I live in central New Hampshire had a unique truss that was a partial scissor truss.
The truss had a short bottom chord for a short distance where it came up off the exterior walls and then the bottom chord flattened out until it approached the other exterior wall.
Here I am at the job site with the truss! Watch this video to see this unique scissor truss.
This truss was used in a large garage where the owner wanted a taller ceiling, but this truss could have just as easily been used indoor where a homeowner had a large room they wanted some sloped ceiling as well as flat in the same room.
Remember, the closer you get to the actual exterior slope, you negate the impact of the interior truss components. A true cathedral ceiling using regular rafters mimics the actual roof slope because each rafter becomes a large beam.
Can You Mix Scissor Trusses With Normal Trusses?
Yes, you can mix and match trusses! Over part of your home you can have scissors trusses, while over another part you can have common ones and over the garage, you can have attic or storage trusses.
The cool thing is that from the outside no one would ever know since the exterior roof slope of all the trusses is identical. Ask your builder to explore all truss options including attic trusses and storage trusses!