I am rehabing an ‘L’ shaped porch on an old Victorian in N.Y.. The corner of the ‘L’ has a bumped out octagonal shape. Total area of ~700 s.f.. Although because of a large overhang on the main roof above that has a yankee gutter, the exposure to rain is probaly only 500 s.f.. The pitch is about 5/8″ in 12″. Very low. To simplify the owner and I decided to do away with the original built-in gutter and just slope the roof all the way to edge and install drip edge.
The porch has 10 columns and on the roof deck above each column I’ve anchored 6″X6″ posts to the plywood deck for railing posts. They will eventually be wrapped with trim after the roofing is installed, covering the flashing.
Couple of questions:
1. I’ve installed peel and stick membrane as flashing around the bottom 8″ of the 6″x6″ posts and along the entire outside 36″ perimeter of the roof as per Grace’s detail for skylights. Mistake? Will rubber roll roofing adhere to a product like Grace ice and water shield?
2. Should I install the drip edge onto the plywood deck or on top of the peel and stick membrane underlayment? My thought being it might be good to really secure the underlayment under the drip edge. I don’t want the peel and stick to lift along the edge. The horizontal dimension of the drip edge is 2 1/4″.
3. I am going to install two 4″ round copper drop tubes thru the sheathing and soffit and connect to downspouts. This is really only to handle the two leaders that drain part of the upper main roof of the house onto the porch roof. I was thinking of essentially ‘plugging’ the leaders into the downtubes. The drop tubes (down tubes?) are attached to a flat 12″ square flange that would sit on the deck. Should I attach directly to the plywood deck or overlap the peel and stick underlayment with the flange?
4. Should I provide for venting hidden behind the drip edge? The cornice is comprised of crown, fascia, bead board soffit to a boxed in beam, and a full bead board ceiling under porch. Although it is not over an interior space, the roof system is enclosed. Is it better building practice to allow for air in and out?
Thank you much, Mike w
Replies
1) "Mistake? Will rubber roll roofing adhere to a product like Grace ice and water shield?"
rubber roll roofing is a nickname that is not specific enough to know what you are using. Read the product literature to answer this. some modifieds are fine, but EPDM rubber is incompatible with any bituminous product
2) re the drip edge, typical detail is one ply of membrane to the edge, then the metal, then seal that to the first membrane with a 6" wide of same membrane. same detail basicly with the drop flange
4) it is usually better not to vent a porch roof space. When the porch is not closed in, there is no pressure to drive moisture into that space, so no need to vent it back out again.
The weakest poiint in all this is that you have penetrated the roof surface with the posts. Where membrane rolls up them, you end up with a edge facing up to catch rain. That needs to be flashed with metal let into the post or make a trim box that drops down over the post and the flashing so the finished post is a 6x6
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Glad you jumped in. I've clicked on this thread twice and just couldn't muster the enthusiasm to answer this question again.http://grantlogan.net/
But you all knew that. I detailed it extensively in my blog.
...and to think that I considered lobbing it to you;)
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Grant,
how do i get to your blog?
how do i get to your blog?
That's a joke, son.http://grantlogan.net/
But you all knew that. I detailed it extensively in my blog.
Thanks very much for the reply. I'll probaly be using a mop down or self-adhered bitumen top sheet. I'll have to read some product literature about base sheet, etc.. The porch is in Brooklyn, NY where torch down roofs are a no-no on residential wood frame houses.
The 6"X6" posts with the peel and stick and eventual rubber roof flashing will eventually be trimmed over to a final dimenion of about 9"X9". I figured the finished external post would serve as counter flashing.
I wrestled with the post design for a while; whether to pass the posts thru the sheathing and anchor to the rafters, or sit them on top of the finish roof, etc. Eventually set up a level platform and routed a flat square for some Simpson brackets to sit, gluing and screwing.
"I figured the finished external post would serve as counter flashing. "You got it
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