Expert: Dave Johnson - 9/9/2009

Question
I want to add an addition to my house 20' by 20'. I wanted to know how to build a girder truss that will expand 20' in the air with no interior supports at 2' spacing and extending 18". I know that I will need 11 trusses.

Answer
Hi Art,
If there in so 2nd storey in this addition, why not just truss your rafters/joists and let that be your ceiling as well?
A standard gable truss is very reasonable to buy, and easy to build too.
Use a 2"x6" rafter (top chord) and a 2"x4" bottom Chord. Then make your web (a "w" shape) by going from the ridge down at an ang e to points 1/3 in from both ends and back up to points 1/2 the rafter length.
I hope this isn't too confusing, but mail me again if it is...
Dave