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Thread: Double Vision

  1. #1
    Patrick McCaffery's Avatar
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    Default Double Vision

    While inspecting the roof of a 14 year old house, I discovered two layers of shingles along the outside edges of the roof. There was only one flashing and the bottom layer of shingles appeared to be the same, color and texture as the top layer. Viewing from the attic hatch did not show double rows of nails. Do roofers sometimes add a layer of shingles arount the outside edge of the roof for extra protection?

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  2. #2
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    Default Re: Double Vision

    Quote Originally Posted by Patrick McCaffery View Post
    While inspecting the roof of a 14 year old house, I discovered two layers of shingles along the outside edges of the roof. There was only one flashing and the bottom layer of shingles appeared to be the same, color and texture as the top layer. Viewing from the attic hatch did not show double rows of nails. Do roofers sometimes add a layer of shingles arount the outside edge of the roof for extra protection?
    I believe they do. One reason I've heard: to direct rain inward so more of it gets into the gutters.


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    Default Re: Double Vision

    Just to be clear, is this an additional layer of shingles in addition to the starter course (marked with an arrow below) at the eaves?

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    Default Re: Double Vision

    I thought you were talking about the rake edges.


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    Default Re: Double Vision

    Quote Originally Posted by Michael Thomas View Post
    Just to be clear, is this an additional layer of shingles in addition to the starter course (marked with an arrow below) at the eaves?
    Michael,

    No.

    That *is* the "starter course", they just used regular 3-tab shingles flipped around backward with the slots up. Does the same thing as a "starter course strip".

    On top of that goes the "first course" of shingles.

    Besides, you would *not* want an additional layer of shingles along the drip edge, that would just create a dam and hold water back.

    Like John, I thought Patrick was referring to the rakes. I've never done it that way along the rakes, but I've heard of other doing it like that for the reason John gave. To me, if that is the reason, why not just install a low gravel stop for the rake drip edge? The small raised edge of the gravel stop would do the same thing, only better, and would not create a lateral cross-flow across the roof like installing two layers down the rake would.

    Jerry Peck, Construction / Litigation Consultant
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    Default Re: Double Vision

    Jerry,

    I read "outside edge" as possibly meaning "eave", if that's the case it seem to me that we need to know for sure that what's been identified as "two layers of shingles" (as seen at the eave) are not the normal starter and first course.

    If "outside edge" means "rake", then the "two layers of shingles" is a different issue.

    IMO, this uncertainty is a good example of why we should try to use specific terminology to unambiguously identify systems and components when communicating with each other and the trades.

    Last edited by Michael Thomas; 02-22-2008 at 09:28 AM.
    Michael Thomas
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    Default Re: Double Vision

    it is commonplace here to run shingles up the rake with the grooves facing in.it provides a clean edge from underneath when looking up and is a guide for a uniform overhang when installing the end of the run shingle.


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    Default Re: Double Vision

    That *is* the "starter course", they just used regular 3-tab shingles flipped around backward with the slots up. Does the same thing as a "starter course strip".
    Just to further clarify, the starter course in the diagram IS a regular full shingle turned 180 degrees, AND THAT IS WRONG.
    The correct installation does not use the full shingle turned backwards, that is... well backwards, and does not follow the installation instructions provided by any manufacturer that I have seen. That is the standard practice around here, but that does not mean it is right.
    That installation is more prone to wind damage since the self-seal strip is at the top of the first course instead of at the bottom edge like the manufacturer instructs.

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    Default Re: Double Vision

    Quote Originally Posted by Jim Luttrall View Post
    That installation is more prone to wind damage since the self-seal strip is at the top of the first course instead of at the bottom edge like the manufacturer instructs.
    Except that, at least in South Florida, those tabs on the first course were adhered down with a plastic roof cement - they were not going anywhere without the rest of the shingle and starter strip below going with it, which, of course, did happen on occasion.

    Jerry Peck, Construction / Litigation Consultant
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  10. #10
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    Default Re: Double Vision

    Jerry, where do they nail through the starter strip?
    Around here, they continue to nail at the adhesive strip which leaves the bottom of the strip to flap in the wind along with the top tabs.
    Are there alternative installation instructions for your area?
    I'm sure the manufacturer would have to provide documentation for any changes in their instructions.
    Of course most of the shingles sold in "non high wind" regions could not be installed in the high wind regions, but for the rest of the country we still have the issue of installers making up their own rules.

    Jim Luttrall
    www.MrInspector.net
    Dallas, Texas

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