help with ridge board / beam design
help with ridge board / beam design
(OP)
i have a gable roof on my house. if i added a gable dormer to the attic to align with the existing ridge, do ineed to reinforce the existing ridge beam? and, what if i want to have structural valleys for the dormer addition? does that effect the existing ridge?





RE: help with ridge board / beam design
I know the answer is not very clear, but it really depends on the exact current roof load path.
RE: help with ridge board / beam design
Are you sure the ridge is a ridge beam?
When you have opposing rafters and the horizontal loads taken by the ceiling joists the ridge is not a beam. the collar ties are not there to take the horizontal loads do to gravity loads. There is a great deal of question as to the value of collar ties but I belive the general opinion is that they are primaarily used to prevent a spreading of the rafters due to wind loads. if you check the design of rafters without ceiling joists and without a structural ridge beam you will find they are overstressed in bending at the collar ties.
That said, after you have verified the the ridge is actuallity a ridge beam then you must calculate any additional loads to the beam in the manner you construct the dormer and determine if the beam needs to be strenghtened.
RE: help with ridge board / beam design
If the dormer(s) are large....you will need to reinforce the ridte board to have it behave as a ridge beam.
The best thing to do is hire a local structural engineer to evaluate you condition.