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Discussion Forum

Roof leak playing hide and seek

mwgaines | Posted in General Discussion on January 2, 2009 10:45am

Guys, I have a roof leak that is driving me nutz. It drips water around the cap for the stove exhaust vent. It’s a fairly slow drip that I can clearly see. I went up on the roof and attempted to thoroughly seal any penetrations around the flange. I also inspected the adjacent areas for any problems, but I didn’t see anything of concern. Here’s the wierd part: Sometimes it leaks; sometimes it doesn’t. Before I sealed it, it leaked any time it rained. Now it just leaks on occasion. I sprayed it with a water hose to try and determine the point of entry, but it remained dry. Then it leaked the next afternoon after a moderate rain (no heavy wind). Can you guys offer any suggestions?

 

New knowledge is priceless. 

Used knowledge is even more valuable.

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Replies

  1. Riversong | Jan 02, 2009 10:49pm | #1

    Sure.

    Remove it from the roof and duct it out a sidewall where it belongs.

     
    Riversong HouseWright
    Design *  * Build *  * Renovate *  * Consult
    Solar & Super-Insulated Healthy Homes
    1. User avater
      FatRoman | Jan 03, 2009 08:44pm | #17

      What happens when the sidewall is CMU faced with brick?Curious when the concern of an extra roof penetration is outweighed by the effort involved in finding an alternative route.'Man who say it cannot be done should not interrupt man doing it' ~ Chinese proverb

      View Image

      1. Piffin | Jan 03, 2009 11:15pm | #19

        Not a thing wrong with roof penetrations as long as they're done right. A lot of the time there are advantages in the fact there are generally fewer elbows when you vent straight up and out 

         

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

      2. mwgaines | Jan 04, 2009 12:05am | #20

        "Curious when the concern of an extra roof penetration is outweighed by the effort involved in finding an alternative route."

        The penetration already exists. If I route the vent to a sidewall, I'll have to patch the roof where the penetration is. Either way, I have a hole in the roof that needs fixing. New knowledge is priceless. 

        Used knowledge is even more valuable.

      3. Riversong | Jan 04, 2009 11:04pm | #24

        What happens when the sidewall is CMU faced with brick?

        Curious when the concern of an extra roof penetration is outweighed by the effort involved in finding an alternative route.

        There are tools for creating an opening in masonry.

        It's not just an additional roof penetration (which is problematic in the OP' case) but ducting a kitchen or bath fan vertically almost guarantees condensate return (or even wind-driven rain penetration). 

        Riversong HouseWright

        Design *  * Build *  * Renovate *  * ConsultSolar & Super-Insulated Healthy Homes

  2. catfish | Jan 02, 2009 10:54pm | #2

    Its coming down the pipe? See if there is a ring around the pipe and seal it .

    1. mwgaines | Jan 03, 2009 12:16am | #3

      There's no pipe connected yet. This is a remodel that I've been working on forever. I need to get this leak fixed so I can drywall the ceiling.New knowledge is priceless. 

      Used knowledge is even more valuable.

      1. Snort | Jan 03, 2009 12:27am | #4

        Can you post a pic of the boot on the roof? and maybe one of what's upstream from the boot?http://www.tvwsolar.com

        Now you see this one-eyed midget

        Shouting the word "NOW"

        And you say, "For what reason?"

        And he says, "How?"

        And you say, "What does this mean?"

        And he screams back, "You're a cow

        Give me some milk

        Or else go home"

        1. mwgaines | Jan 03, 2009 12:50am | #5

          I'll see if I can get one tomorrow.New knowledge is priceless. 

          Used knowledge is even more valuable.

          1. Snort | Jan 03, 2009 03:39am | #7

            Great ,post'em, boobys will figure it out, send you a bill, split it with the rest of us, and we'll all get a kickback, which we'll apply to a flight to the Bahamas for our super secret BT don't tell anybody graft yo gran ma vacation... oh s h i t, now you have to die.http://www.tvwsolar.com

            Now you see this one-eyed midget

            Shouting the word "NOW"

            And you say, "For what reason?"

            And he says, "How?"

            And you say, "What does this mean?"

            And he screams back, "You're a cow

            Give me some milk

            Or else go home"

          2. bobbys | Jan 05, 2009 01:44am | #28

            First i pull up to this job and theres 20 guys fightin for it and now theres to much bear chiit on the vent;]

  3. JoshRountree | Jan 03, 2009 03:17am | #6

    Just throwing this out there, could it be condensate?

    1. mwgaines | Jan 03, 2009 05:12am | #9

      Condensate? Hmm...

      I don't really think it is, but it would help explain the peculiar nature of this leak. New knowledge is priceless. 

      Used knowledge is even more valuable.

      1. Piffin | Jan 03, 2009 04:51pm | #15

        condensation was my first thought until you said nothing is hooked up to it. When it rains, the air is generally cooler and more humid so there would be some condensation on cold metal surfaces.So is the ceiling finished so the attic is isolated from the living space?
        what form of heat are you using?
        Living there yet?
        Other sources of extra moisture? 

         

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

        1. mwgaines | Jan 03, 2009 08:35pm | #16

          "So is the ceiling finished so the attic is isolated from the living space?what form of heat are you using?Living there yet?Other sources of extra moisture?"

          The house is gutted and being prepared for drywall (i.e. no ceilings -- you can see the roof from the floor). I do have a functioning electric heat pump, but the drip occurs even when the system has been off for days. I am not living in the house yet. There is no plumbing or other sources of moisture in that area. BTW, we had a light rain this morning and it hasn't leaked a drop, as far as I can tell.New knowledge is priceless. 

          Used knowledge is even more valuable.

  4. MikeRyan | Jan 03, 2009 03:45am | #8

    When I have this problem, I try the following:

    "Olly Olly Oxen Free"

     

    :-)

  5. davidmeiland | Jan 03, 2009 07:36am | #10

    "stove exhaust vent"

    Is this from your range hood or a gas heating stove with a flue?

    1. mwgaines | Jan 03, 2009 04:35pm | #12

      "Is this from your range hood or a gas heating stove with a flue?"

      Range hood.New knowledge is priceless. 

      Used knowledge is even more valuable.

  6. User avater
    johnpjackson | Jan 03, 2009 09:25am | #11

    Could the water be entering from somewhere further away up the roof at a higher elevation and traveling all the way back to where the pipe comes through the roof? That might explain why hosing down there area where the pipe is didn't reproduce the leak but a light rain the next day did. Attempts to seal the pipe could have partially blocked where the water was running down around it too, but that still would leave open the question of where the water was making it's initial entry under the roofing materials.

    1. mwgaines | Jan 03, 2009 04:38pm | #13

      "Could the water be entering from somewhere further away up the roof at a higher elevation and traveling all the way back to where the pipe comes through the roof?"

      Only thing above is the ridge vent and it "appears" to be in good shape.New knowledge is priceless. 

      Used knowledge is even more valuable.

      1. catfish | Jan 03, 2009 04:42pm | #14

        metal or shingle-over ridge vent? metal will leak in blowing rain

  7. User avater
    Dinosaur | Jan 03, 2009 09:05pm | #18

    What's the pitch of this roof? What is the orientation to the prevailing winds? What is the age/condition of the shingles? How long after it starts raining does the leak start dripping...and how long does it take to stop dripping after the rain quits?

    Dinosaur

    How now, Mighty Sauron, that thou art not brought
    low by this? For thine evil pales before that which
    foolish men call Justice....

    1. mwgaines | Jan 04, 2009 12:16am | #21

      "What's the pitch of this roof?"

      ~ 4/12

      "What is the orientation to the prevailing winds?"

      The leak is on the north side of the house.

      "What is the age/condition of the shingles?"

      About 12 years I think, but fair condition.

      "How long after it starts raining does the leak start dripping...and how long does it take to stop dripping after the rain quits?"

      It doesn't always leak. When it does, the drip stops within 5 minutes or so after the rain stops. It leaks about 3-4 drops per minute. New knowledge is priceless. 

      Used knowledge is even more valuable.

      1. User avater
        Dinosaur | Jan 04, 2009 06:26am | #22

        With a relatively low slope like that, and facing the prevailing winds, I am thinking there might be a buildup of roof patch cement sufficient under some circumstances to create a small, localised dam that could retain enough water above it to weep back up under the shingles and cause this small leak.  Granted, this is a bit of grasping at straws, but I am assuming you've already tried what anyone else would have--gooking up the suspect area good and thick with patching compound.

        The only suggestion I've got at this point would be to strip back the area around the leak right to the roof deck, lay some ice-and-snow membrane, then re-shingle & re-flash it.

        Dinosaur

        How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....

  8. IronHelix | Jan 04, 2009 04:37pm | #23

    For a year I battled an "eave" leak on my shop and eventaully after many "on and off" leak episodes similar to what you mention I decided to remove the 8 year old shingles on that roof plane and replace.

    I asked my helper to let me tear off the areas of leak at the eave so I could find out exactly what was causing the leak.  As I chased the water marks up the roof it became apparent that the leak was coming from the heater flue boot 12 feet up the roof plane.

    As I took apart the properly laid shingles and the correctly set boot flashing I found that the metal boot seam at the horizontal plate and the vertical cone had failed in the seam.

    That boot never dripped into the building at the penetration, but the water followed down the plane of the felt paper to a tear about 2 feet from the edge and there it leaked.

    Leaks are often "sneaky".......go outside the box to find the problem.  Re-shingle may be your only way to chase down your crazy leak.

    Good Luck............Iron Helix

  9. seeyou | Jan 05, 2009 12:02am | #25

    You're probably going to have to take it out and re-install it. Smearing stuff around it will probably be fruitless at this point. Also, it's possible that one of the joints where the separate pieces of the jack connect together is leaking. If the jack is not fairly new, I think I'd remove it and install a new one using I&WS around it before re-shingling.

    http://www.quittintime.com/      View Image        

    1. theslateman | Jan 05, 2009 12:06am | #26

      Grant .

      The best response so far  -seems like condensation was ruled out.

  10. KaneoheBay | Jan 05, 2009 12:10am | #27

    Contact a roofer with infrared equipment. He'll find the leak (moisture) path quickly.

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