Engineered Scissor Truss

[dick]

I have a house plan design using scissor trusses spanning 33'-0". Top chord pitch is 10:12. Bottom chord pitch is 7:12. I'm told the rule of thumb for bottom chord is 1/2 the pitch of the top chord. Are there exceptions?

[Rich]

Rules of thumb are just that.. guidelines. If you have them engineered they will pretty much make whatever you want work. As an aside - I've always used 3 as a negative pitch.. top pitch being 10/12 and bottom pitch 10-3/12 or 7/12 pitch.

[AUGER]

hey guys...
first post here....
You can get scissor trusses in pretty much any pitch you require
the 3/12 rule of thumb applies to standard scissor truss configurations...

if you want 10/12 over 9/12 for example the key here is to allow enough depth at the heel(over the wall) ie heel height.....to still allow the truss to work....and to limit the live load deflection

same applies to parrallel chord trusses (same inside and out side pitch)

with 33 feet as a span and depending on snow load conditions...
you would require a minimum of 1'4" heel and up to 2' heel could be possible..
then you could increase your interior pitch....

hope that helps....
Auger

[kadoka]

I am getting ready to build a garage and just had scissor trusses priced. I wanted 12-12 on the outside and 9-12 on the inside. The price was $2800+. If I change the inside to 8-12 instead of 9-12 the price drops to $1800+. Big difference. I think I can live with 8-12 pitch on the inside. Will just build a short knee wall to compensate for the lower ceiling height.

[Don_P]

Kadoka,
You understand there is no "floor" in a scissor? Maybe I'm reading wrong, ain't the first time :)

[kadoka]

Don

Of course. There will be a floor above the garage and this will leave a completely open area above the garage. The knee wall will sit on top of the ceiling/floor above the garage area.

[11chaos]

Why aren't you just using the Truss for attics? Or making rafters? That would allow you to use any pitch you desired.