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Diagnose Chimney Rot…

JFink | Posted in General Discussion on March 30, 2009 05:37am

So I got a note from one of the students in my latest eenrgy efficiency class at our local adult ed…he stumbled upon some nasty fungal growth in his chimney chase while inspecting his attic for air leaks. (see chimney.jpg)

It seemed pretty unlikely that the water was accumulating on theinterior and causing damage to that extent, especially that close to a warm flue pipe. I figured the damage must be coming from the outside.

Outside pic reveals that the chimney is faced in brick (great…) and some rust discoloration. I haven’t gone on the roof yet, but I thought I would toss it out to you old hats and see if I’m missing anything obvious…

Justin Fink – FHB Editorial

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  1. FHB Editor
    JFink | Mar 30, 2009 05:38pm | #1

    oh yeah...here are some re-sizes:

    Justin Fink - FHB Editorial



    Edited 3/30/2009 10:43 am ET by JFink

    1. FHB Editor
      JFink | Mar 30, 2009 05:43pm | #2

      and the exterior...Justin Fink - FHB Editorial

      1. Piffin | Mar 30, 2009 06:01pm | #4

        You saved yourself from a beating for the picture size just in time there junior, LOLThose are not brick, but slim brick facings, and I see no sign of any kind of flashings under them tying to the shingles, so there is little doubt that some water is getting in thru that exterior system. I've also seen caps like that metal one screwed down with regular heet metal screws instead of gasketed tec screws so there could be water getting in at top.But this location is also a very common spot for condensation problems because it is highest in the attic, and not airtight so warm moist tries to exit there. And a triple wall chimney is not all that warm even in use and many only see occasional use. Mike Maines just had a thread trying to diagnose and solve a similar problem. I like to see a metal air stop cut and caulked around the flue pipe to prevent drafting to the upper chase there, and make sure the rest of the attic there has balanced venting.Looks to me like that chase is gone by enough to need to be rebuilt and do it right this time. 

         

        Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

      2. seeyou | Mar 30, 2009 06:04pm | #5

        I second Eric's guess that's peel and stick brick. There's no counter flashing. It looks like there's some kind of base flashing, but it's tough to tell how it's actually flashed.http://www.quittintime.com/      View Image        

      3. gzajac | Mar 31, 2009 01:56am | #9

        Justin

        I would look at how the metal chimney pipe is flashed going through the metal flat top. I have seen too many termination tops screwed to the last piece of pipe, and the pipe caulked to the flat top, no flange, just a full tube of silicone.

        Sometimes they put a collar in the hole, then run the pipe through, and use a storm collar. They caulk the collar with cheap caulk, it hardens, falls off, then leaks onto the plywood subcap, and rots it.

        If you get on top, see if they nailed that top down with some electroplated roof nails, probably rusted through by now.

        Probably no kind of barrier behind that fake brick to shed the water, sure does look pretty though.

        Put the ladder up there, and tell us what you see.

        Greg in Connecticut

      4. Henley | Mar 31, 2009 02:07am | #10

        That stain down the face sure points to a
        leaky cap. It looks like the stain carries right down the shingles too.

    2. Henley | Mar 31, 2009 02:09am | #11

      You can clearly see the Z-brick cut around the ridge cap. What we have here is phony bologna.

      1. Piffin | Mar 31, 2009 02:39pm | #12

        I'm still not convinced there is ANY flashing in there. Even at the second story wall to the right. 

         

        Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

        1. gzajac | Mar 31, 2009 02:54pm | #13

          I think there is step flashing there, unfortunatelty it is on top of the wrap, and just behind the wire mesh.

          If that top has been there any amount of time, it could be rusting on top, the nails could be rusting, or the storm collar could be rusting, which all could lead to rust running down the face and onto the roof shingles.

          I love how they headered off that rafter that got in the way.

          Greg in Connecticut

          1. Piffin | Mar 31, 2009 02:59pm | #15

            It is headered at the bottom.reason I suspect no flashing, is that you will generally see some dimensions hint of it,esp at corners in the shingles. And the down side of both locations shows me nothing. The siding is tight down to the shingles which is wrong and might be so to hide the fact. Lots of caulk at the chase brick to shingle intersection 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          2. gzajac | Mar 31, 2009 08:52pm | #19

            Piffin'
            I need better glasses, there sure is a header. I am dying to find out what Justin discovers.Greg In Connecticut

          3. Piffin | Mar 31, 2009 11:03pm | #20

            Will really be glad to see picture of the top of cap. Lot of different possibilities have been mentioned there. 

             

            Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

          4. FHB Editor
            JFink | Apr 01, 2009 12:30am | #21

            Well, I guess I'm the only one NOT looking forward to it :)Justin Fink - FHB Editorial

        2. danski0224 | Mar 31, 2009 02:57pm | #14

          There is a tiny bit of flashing poking out on the lower right of the second picture.

  2. User avater
    EricPaulson | Mar 30, 2009 06:00pm | #3

    On the outside picture, you can see a vertical crack.

    I'd bet $10 that ain't brick. They're glued on brick faces. Can't see the sheetmetal cap to tell what is going on up there. Flashing looks like a mess too.

    I'd say it's a do over.

     

    1. Piffin | Mar 30, 2009 06:06pm | #6

      What flashing?!;)I see another major problem unrelated to the moisture thing.A flue needs to be 3' above the ridge or two feet above any other portion of the structure within ten feet of it. There is a second story eave only 4-5 feet horizontal to the right from that chimney cap. It probably draws poorly in certain wind/weather conditions. 

       

      Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

      1. User avater
        EricPaulson | Mar 30, 2009 06:18pm | #7

        I never even noticed that I could scrool right.

        Good call on both counts. I had not even considered closing off the chase at this point. 

        1. Piffin | Mar 30, 2009 06:24pm | #8

          I looked more...That rust stain spilling down from the top cap at a corner is in about the same location as the worst of the rot shows inside. I'm betting the worst of the leakage is at thee top near that corner from a fastener.By scrolling down the inside view, you can also see a rust stain flowing from the joint of the flue pipe where it joins an elbow. That confirms to me that it is triple wall and that it does not stay warm in constant use, but occasional use creates condensation in the pipe itself. A triple wall under constant use will stay warm and dry in the segments. 

           

          Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

  3. wane | Mar 31, 2009 03:07pm | #16

    The "rust" stain is not rust, it's creosote .. the wood where the fungus is looks like it's perpetually soaked.  I have seen ice build up in areas like that where air currents flow on a continual basis.  The ss chimney pipe needs a cap, and I hope someone painted it black above the chimney, or someone needs the chimney cleaned badly.  Check the pipe where it passes thru the chimney cap is well caulked .. like others, maybe there's step flashing under the chimney, maybe there isn't ..

  4. danski0224 | Mar 31, 2009 03:15pm | #17

    My $.02....

    There are no nails visible on the sides of the chimney cap. The sides of the chinmey cap are "fake brick". I would suspect that the chimney cap is face nailed on top. The picture taken from inside shows the water damage originating up high from a single point.

    The flue pipe appears to terminate not too far above the chimney cap. Prevailing winds could be blowing the flue gases down onto the chimney cap, rusting it. It is doubtful that a single nail is causing the rust stains. The unknown is the extent of the rusting on the chimney cap.

    It looks like there is an issue with the chimney termination not being 2' higher than anything within a 10' radius- if it is a woodburning fireplace I believe it is 5'.

    If the chimney chase is storebought, the flashing is probably built-in as part of the base used to anchor the assembly. I am assuming if there was a problem with the flashing around the fake brick that other damage would be visible. Caulking at the roofline is not a good sign, though.

    Obviously, these fake brick panels are seamed at the corners. If the caulking used there has failed (or if non was used), water will get in there at that point.

    Low bid fireplace installers use a tube of caulk to seal the flue pipe to the cap, instead of a proper collar and storm flashing. That problem won't be known until someone gets up there.

    1. FHB Editor
      JFink | Mar 31, 2009 04:01pm | #18

      Thanks for all the checklist items, everybody. If I get up on the roof I'll make sure to snap some photos...if only to help the next guy!

      It sure sounds like this is going to turn into a rabbit hole of a job, though. Justin Fink - FHB Editorial

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