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The guy who sold me the shop gave me an unopened roll of self-adhesive membrane (ice dam stuff). Since we don't really have problems with ice dams here, can I use it to step flash the shop skylights instead of metal flashing? Or is it used as a backup instead of the flashing?
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David
The chief cause of failure in this life is giving up what you want most for what you want at the moment. -
that is some great stuff man! peel n seal is one name it goes by and it is a self healing membrane. Nail holes are sealed around. I would put that under the flashing and its not only for ice dams. I know of some people who did their entire roofs with it. Now....it is pricy to do that with, but in FL you can get a rebate if you tape all your seams with the stuff, they call it a secondary water barrier, in case your tar paper comes flying off.
hey, it happens down here. 
I think in straight lines, but dream in curves
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Ok so step flash with metal and use it as backup. Thanks. I was wondering if it could be exposed direct to weather but if folks do a roof with it then I guess it can. I was thinking I could also use it to counterflash the vertical sides of the skylights over the step flashing.David
The chief cause of failure in this life is giving up what you want most for what you want at the moment.Comment
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It depends on the actual material. Some of the peel & stick membranes will break down with prolonged exposure. I think it's mostly UV related. Several manufacturers publications I've read when researching products called out a certain amount of exposure time. If I recall correctly, most were in terms of weeks, maybe months.
It should give you a really good seal, but I'd check with the manufacturer before using it in exposed locations.ErikComment
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Most peel and stick will break down from direct exposure to sun light. Google the name of the product (it should be on the foil side of the peel and stick)Comment
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I installed my shed skylight with stepped metal flashing over a peel and stick underlayment. It was the recommended installation method for Velux skylights. I have build pics somewhere but if you Google velux ECL you should see their installation PDF. The underlayment is cheap insurance - or free for you.
Here's a link (it took a few minutes to download):
http://www.domwebx.com/inet/techdocs.nsf/All+Tech+Docs+-+web+display+-+new/F3506428794CC7BA852572610072F852/$FILE/ECL 451102-0207a.pdfComment
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Harmsway, thanks for the link. There is already peel n stick but it is stuck directly to the roof decking. I think what I am gonna do is put more down that is on top of the roofing felt, then add the step flashing on top of that. At least if water does get through it will run down the felt.David
The chief cause of failure in this life is giving up what you want most for what you want at the moment.Comment
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Underlayment should be even better above and below roofing felt, although it may get a little thick. Interweave the step flashing with the shingles though. Think of the whole system (felt, underlayment, flashing and shingles) as layers of shingles and imagine yourself as a drop of water flowing down the roof. You (the drop) should never be directed towards the roof - always away.
BobComment
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A lot of or details we do, especially in window openings and even more so with skylights, we call out an adhesive membrane (peel & stick) sealing the frame to the sheathing. Sometimes that can be done by caulking under the nailing flange. The building paper or felt goes on top of that, then another peel & stick on the felt adhered to the frame. I like doing it that way to help keep any water that gets under the other membranes from going into the structure through the opening.
Tyvek has a lot of good details and installation details using their straight flash and flexwrap.ErikComment
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