Roof Work: Vent Stack Gaskets and Shingle Fungus

Part of the spring ritual involves cleaning the maple seeds out of the gutters, which also gives me an opportunity to inspect things up there. This year brought a revolting discovery:

Rotted vent stack gasket
Rotted vent stack gasket

It seems the rubber (?) seals around all three vent stack pipes have disintegrated. Now, the contractor installed these as part of the re-roofing project late in the last millennium, so it’s not like they came with the house. They’re an exact match for what’s currently available at Home Depot and I have no reason to believe new ones will last any longer. Sheesh.

The correct fix involves removing the shingles around the existing aluminum plates, installing new plates, and then replacing the shingles. That seems unwarranted, seeing as how the aluminum remains nicely bonded to everything, so I slipped some solid polyethylene shields around the vent stacks, tucked them under the uphill shingles, and hope that’ll suffice.

The discoloration on the roof is getting worse, except downhill from the chimney’s copper flashing. You can see one of the ugly new black plastic vent seals over on the right:

Copper effect on roof discoloration
Copper effect on roof discoloration

I suspect the copper ions kill off the fungus, so, invoking Science, I tucked a foot of copper wire under the ridge vent uphill from a patch of fungus:

Anti-fungal copper wire test
Anti-fungal copper wire test

We’ll see if that makes any difference. I suppose the next time I’m up there I should tuck a strip of copper flashing under the shingle on the other side of the chimney to see if a bit more surface area will have more effect.

13 thoughts on “Roof Work: Vent Stack Gaskets and Shingle Fungus

  1. You can also use zinc to prevent the stains on roofs. there are two products that came up in a google search for ‘zinc roof stain’. z-stop and zincshield are both just rolls of zinc tape you nail at the top of your roof. might be more effective than just a single copper wire?
    LJ

    1. might be more effective than just a single copper wire?

      There’s no doubt about that!

      That pitiful copper wire was more in the nature of an experiment than a real treatment; I simply observed that there was no stain downhill of the copper flashing.

      Now that I know about zinc tape, I’ll check the local big-box stores to see if it’s available… thanks for the tip!

      1. Silver works even better…
        One reason that copper plumbing was so popular was because it’s bacteriostatic and a bit bacteriocidal. I seem to recall it inhibits cell wall formation, so it’s not a problem for animals but it’s toxic to bacteria.

        1. it’s not a problem for animals

          I vaguely recall that copper is murder on fish … *googles* … uh, copper sulfate, at least, is bad stuff. On the other paw, I think a strip along the roofline can’t possibly be a Bad Thing.

          Maybe this calls for a nice wire dipole antenna in, say, the 20 meter band…

    1. I’m a cheapskate who figures one strike in half a century doesn’t justify ten grand worth of copper and labor…

      But I don’t have any copper on the roof as an antenna because I figure the instant I wire it up, a lightning strike will blow the house apart.

      I can debate both sides of the issue with equal facility!

      1. Is it that expensive? It looks like around here for a house of around 20×20 with a top height of 10 it’d be around €2000, with another €950-1000 for the stuff that protects the electricity that’s incoming through your neighborhood cabling (i.e. electricity lines as well as telephone and TV). Granted, it’s still a fair bit of money, but less than half of the amount you mentioned.

        But aside from that it’s apparently normal enough to go without it that it’s not an issue with insurance? From the pictures it looks like you’re living in a free standing house (detached house? not sure of the terminology) and afaik since that tends to increase chances of hits, fire insurance tends to be unwilling to insure you without a lightning rod. In the case of townhouses that’s different on account of whatever cost/benefit analysis they do.

        1. Ten grand is a rough estimate; every time I’ve tried to estimate *any* project around here, I’ve been low by a large factor. I know that was half the bill for a lightning protection project a friend did maybe a decade ago, but he had a much larger house atop a much larger hill…

          it’s apparently normal enough to go without

          Although we’re atop a local maximum, the surrounding ridges are much higher. Over the last decade there have been two or three other strikes in the immediate area and one really near miss, but nothing out of the ordinary.

          So far, anyway…

        2. Whoa, that’s close.

          Personally I’ve got the remaining walls and ashes of the house that was struck by lightning burned into my pupils and it comes up whenever I think of no lightning rods. It was only a couple 100 meters away. But then that was flat land, nor where there any trees nearby it. Still, who knows what kind of damage a nearby tall tree might do if it served as a lightning rod.

  2. The Best of Ciarcia’s Circuit Cellar on page 204 “How lightning strikes” . Classic stuff…

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