I am currently building a detached, single car garage and getting ready to sheath the roof. I had originally specified a ridge vent but am strongly considering switching to a gable vent. I have some reasons for making this choice which I'm not looking to discuss here.
My question is, if I install gable vents, will I need to modify my end trusses? These are the end truss plans:
Left as-is, the gable vent would be partially blocked by web ST2, which is untreated lumber. I'm not concerned about the limit to airflow, rather the fact that this web would be partially exposed to the elements.
If I do modify the truss, I assume this would be similar to window framing?
- Twin 2×6 header
- Twin 2×4 bottom plate/sill
- King and jack studs left and right
- Cripple studs centered above and below
Some details of the project:
- 12' by 20' detached, single story, single car garage
- I am not insulating at this time but plan to later on
- I'm in Wisconsin, USA — hot humid summers, cold wet winters
- Trusses are factory made
- Gable ends will have a 1' overhang
Best Answer
The only circumstance under which I'd even remotely consider modifying a truss is if I had an engineer's stamp.
In this specific case, you're thinking about the opening as a simple downward carrying load, and I don't think either of us are qualified to make that assumption. (Trusses probably have side and up loads that aren't obvious to mere mortals.)
I'm not sure why you wouldn't just have an asymmetric vent, or split the vent between two smaller symmetrical vents.