How To Flash This Vent Stack?

Old 09-17-19, 07:07 AM
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How To Flash This Vent Stack?

Hey all. I have an interesting problem and could use some ideas.

I've got a big cast iron vent stack that I need to flash as part of a re-roofing project I'm currently doing. The pipe exits a porch roof and continues for about 20ft up, so removing it is sadly not an option. The original lead flashing was clearly set into the pipe fittings, probably with oakum and molten lead... and it accidentally got busted up removing the old roof, so I've got to figure out a fix.

The first issue is that there are a series of flared bell housings that connect each section of pipe. Any boot I slip over the top would be far too big to make a seal after it clears the flared sections.

So I thought about doing a split lead boot (seam facing downhill of course) except I don't have oxyacetylene to actually weld the joint up. Maybe MAPP gas or Propane would work? Never tried that.

Additionally, I'm not really sure how I would seal where the boot meets the cast iron if I did the split boot idea. I could slather on a bunch of tar, but that's just going to dry out eventually... I thought about tarring the inside and then using a peel and stick membrane as a sort of counter flashing on the outside, but idk... not a whole lot of good options I can think of.

Here's a (bad) picture of what I've got. Ignore the spray foam and 2x4 blocking- it was about to rain and that's all I had on hand! Appreciate ideas anyone has

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