Air sealing, flashing questions
I have to say that reading GBA for 4 years certainly helps when you build your own house (my brother's house, really), but it does not replace actually getting your hands dirty or sticky. I use the term sticky because my job is air sealing and I get covered in sticky stuff daily.
I have a few questions because I am not sure that I am doing things correctly. I don't really "get" flashing. I know you are supposed to "think like water" and ask yourself where would the water go and how to divert it to the outside of the building, but some details still baffle me.
Here's an example. This attachment shows the roof side on one of the shed dormers. The roof consists of plywood, 30# felt, roll flashing over the felt at the wall/roof intersection, one 1.5" layer polyiso taped at seams, then 2 x 4 nailers with 1.5" polyiso between the nailers, then another layer of plywood taped at seams, 30# felt. Seams were staggered so they did not overlap. This will all be covered with a metal roof.
Aside - I thought the second layer of plywood was not necessary, but was overruled by Carlton, the carpenter.
So the flashing that you see in the attachment is the second layer of flashing at the roof wall intersection. My question is when you install flashing do you flash over the felt or not? I think the roofers will add a layer of metal flashing as well. Serious, crazy overkill? I've been doing the flashing so there is no labor cost involved at least.
Next question, what to do at the top of the dormer where the foam is visible. I was thinking about sealing the seams between layers with Prosoco joint and seam sealer and then painting over it with Fast Flash. I cannot find any information as to whether this product works in such an application. I can tape though, it if that would seal it well enough. The carpenters are not used to these air sealing details so they did not tape this side adequately. They are taping the other side of the roof at each side seam of foam and plywood.
Thank you for all your help.
Posted Sun, 08/25/2013 - 12:30
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