Ok guys, I'm a young architect with limited experience, and i was wondering if I could get some sage advice. I have a client that is adding a full second floor to the rear portion of a cape cod house. The only problem is that to be code compliant, I really need to keep the slope over the new roof to 1:12, and the client is INSISTENT upon using standing seam metal. So... is it possible for an asphalt shingle roof with a 9:12 slope to join a 1:12 slope standing seam roof at the ridge? And any suggestions on how to ventilate? Normally I would run Propas from soffit to ridge vent, but i'm concerned about putting a ridge vent along such a low slope and then having rainwater blow back up into the attic through the vent. Even more unsettling... this guy's acting as his own GC.
First;
You can have the sheet metal flashing fold over symetrically and equally onto the 9/12 portion of the roof. Also run similar looking flashing for the remainder of the ridge even where the dormer is not connected for an even continuos appearance.
Second;
You can install a ridge vent below specification level if you insert an j-channel on the interior portion of a ridge vent such as the Shingle Vent II. The longer leg of the metal flashing gets covered by the top edge of the last course of shingles, then their is a 3/4" to 1" perpindicular rise and then the shorter leg runs back at a 90* angle facing the eave edge. This creates an internal baffle in addition to the preexisting external baffle to battle the weather elements.
It is not listed in their application guidelines, but I have done this successfully on many occassions on cape cod roofs with rear low slope dormers.
Third;
If neither of these options are utilized, you can install the one sided ridge vent product manufactured by DCI Products as their One Sided Smart Vent application. This would get installed only along the ridge on the opposite side of the dormer, which would alleviate any of the potential concerns you may have.
thats all well and good but the point is the ss roof will last many years longer and if it goes over the shingles,you`re gonna have a lot of work when the shingles go bad,best to bite the bullet and do it all in ss now
just trying to educate the architect on the thought process,my 1st answer covered it for his question but he should recommend the proper system and tell them why,and the fact that you have to do work again to the back of the metal system when he does the shingle area is important to consider .your answers were good ed,I was just elaborating on it and reasons to do it different-it is his reputation,you don`t want his client calling him on it in 5 yr.s if he left it unsaid,better he suggest it and have them turn it down ,then have them say later "why didn`t you tell me that??that`s why we relied on you!":wink:
Remember, he stated that the HO was GC'ing the project himself. I doubt if he will be springing for additional bucks if he is that way to begin with, and the guy make a comment as to shudder to the thought.
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