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  1. #1
    Join Date
    Feb 2011
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    Oregon
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    Default Gap in roof flashing?

    Roof flashing over the roof of the front porch had about a 3/4" gap under it. Wood blocking about every 16" or so supported the flashing. The builder said there was screening to help vent. My question is if there was a driving rain storm, wouldn't it go under the flashing through your "screened vent" and down into the closed soffit area above the front porch? He says no because there is a negative pressure. What the? I have a picture but its from a distance, but maybe it will help in what i'm trying to explain. I've never seen flashing propped up like this. He said he used to do this in Seattle to help keep moisture and mold from under the flashing. ?? Comments.

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  2. #2
    Join Date
    Aug 2007
    Location
    Memphis TN.
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    4,311

    Default Re: Gap in roof flashing?

    Quote Originally Posted by Steve C. View Post
    Roof flashing over the roof of the front porch had about a 3/4" gap under it. Wood blocking about every 16" or so supported the flashing. The builder said there was screening to help vent. My question is if there was a driving rain storm, wouldn't it go under the flashing through your "screened vent" and down into the closed soffit area above the front porch? He says no because there is a negative pressure. What the? I have a picture but its from a distance, but maybe it will help in what i'm trying to explain. I've never seen flashing propped up like this. He said he used to do this in Seattle to help keep moisture and mold from under the flashing. ?? Comments.
    .
    I guess if the Driving Rain was going up 30 degrees.
    .

    It Might have Choked Artie But it ain't gone'a choke Stymie! Our Gang " The Pooch " (1932)
    Billy J. Stephens HI Service Memphis TN.

  3. #3
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
    Posts
    26,248

    Default Re: Gap in roof flashing?

    That *may* be a counter flashing, and, if it is, then no problem.

    If that *IS* THE flashing ... then it in installed all wrong.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  4. #4
    Join Date
    Feb 2011
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    Oregon
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    Default Re: Gap in roof flashing?

    Quote Originally Posted by Billy Stephens View Post
    .
    I guess if the Driving Rain was going up 30 degrees.
    .
    I've seen some thunderstorms where the rain goes almost upside down. And, I've been called back to a home where a situation (and driving rain) went into the attic area and dripped down through the pendant lights onto the cell phone sitting on the counter. I was asked why I didn't call out that gap in the eave. Small gap I might add. Just trying to cover my a**


  5. #5
    Join Date
    Feb 2011
    Location
    Oregon
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    41

    Default Re: Gap in roof flashing?

    Quote Originally Posted by Jerry Peck View Post
    That *may* be a counter flashing, and, if it is, then no problem.

    If that *IS* THE flashing ... then it in installed all wrong.
    Thanks Jerry. Love this website.


  6. #6
    Join Date
    Feb 2009
    Location
    Southern Vancouver Island
    Posts
    4,546

    Default Re: Gap in roof flashing?

    Right. I would definitely point out the potential for moisture to get in. We see rain splash a foot up the wall quite often.

    The purpose may be to ventilate the enclosed attic spaces there. If so, he should install a ridge vent which is designed for the purpose.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  7. #7
    Join Date
    Aug 2009
    Location
    Michigan
    Posts
    249

    Default Re: Gap in roof flashing?

    Quote Originally Posted by John Kogel View Post
    Right. I would definitely point out the potential for moisture to get in. We see rain splash a foot up the wall quite often.

    The purpose may be to ventilate the enclosed attic spaces there. If so, he should install a ridge vent which is designed for the purpose.
    Take a look at the picture again. It would be a little difficult to install a ridge vent in that situation. Maybe some pancake/pot vents would have been a better choice, but I don't like those either.

    Randy Gordon, construction
    Michigan Building Inspector/Plan Reviewer

  8. #8
    Join Date
    Mar 2007
    Location
    Lake Barrington, IL
    Posts
    1,363

    Default Re: Gap in roof flashing?

    Quote Originally Posted by Steve C. View Post
    He says no because there is a negative pressure. ?? Comments.
    He's right about there being a negative pressure. With a wind driven rain there's a negative pressure in the wall and an positive pressure outside. The wind and pressure differentials can drive water pretty far into a structure. Without some dis-assembly you're not going to know how protected things are. Nothing wrong with writing what you see and what you don't know.

    Eric Barker, ACI
    Lake Barrington, IL

  9. #9
    Darrel Hood's Avatar
    Darrel Hood Guest

    Default Re: Gap in roof flashing?

    This may be a good solution to ventilating the porch's attic, but I would comment that it is an abnormal installation that may lead to water intrusion under some circumstances.


  10. #10
    Join Date
    Aug 2009
    Location
    Michigan
    Posts
    249

    Default Re: Gap in roof flashing?

    I believe something like this is what you are seeing. Roof-2-Wall

    Randy Gordon, construction
    Michigan Building Inspector/Plan Reviewer

  11. #11
    Join Date
    Dec 2008
    Location
    Maryland
    Posts
    2,777

    Default Re: Gap in roof flashing?

    The method for the venting may work and resolve a problem, but just not a complete design to meet need. There needs to be something to physically prevent water from blowing in. Below is my solution though I would question distance from edge of flashing to wall as being adequate. If an extention swas needed an extension could be riveted on to existing material.

    The Ridge Vent For Shingle Roofs

    The RidgeVent for Shingle Roofs | Specifications

    Size: 20' x 10.5" x " / 6.096m x 266.7mm
    14.1 Sq. In. of Net Free Area per Lineal Ft.
    Vent Material: Non-woven, non-wicking matting, UV stable.
    Specially formulated pressure sensitive adhesive will adhere to
    roof shingles.


  12. #12
    Roofmaster 417's Avatar
    Roofmaster 417 Guest

    Default Re: Gap in roof flashing?

    With rain it might be a good argument but Ice ???,,,now that is a whole different story.Somebody has negative pressure between the ears IMO.


  13. #13
    Join Date
    Mar 2007
    Location
    New Westminster, B. C., Canada
    Posts
    165

    Default Re: Gap in roof flashing?

    Hi, ALL &

    It "appears" this was an attempt to do a rain-screened wall assembly - except the wall flashing should be the lowest piece (anything emptying from inside that vented drainage path should flow over - not under).

    Botch-job...


    Cheers !

    -Glenn Duxbury, CHI

  14. #14
    Join Date
    Dec 2008
    Location
    Maryland
    Posts
    2,777

    Default Re: Gap in roof flashing?

    After allowing this to sink in I have to question what the Builder was trying to say in "...He says no because there is a negative pressure ...". Negative pressure from what against what???? May have lost something in the translation.


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