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Metal top flashing for windows

BigRodent | Posted in Construction Techniques on August 16, 2006 12:46pm

I need some opinions here.   On my house I just installed new vinyl windows that have a nailing fin.  Behind the windows the rough opening is wrapped with rubber flashing (Vycor).  The Tyvek is taped over the nailing fin.   Around the window is a PVC 1×5 trim.  The siding is Hardie will butt to the pvc on all sides and caulked.   What is the right way to treat this window at the top?

Option 1) Nothing?  Let the moisture barrier do its work, leave a gap to let moisture escape.

Option 2)  Put metal flashing from under the siding bent over the lip of the PVC trim.  Don’t caulk as to let moisture escape

Option 3) Put on the metal flashing but caulk the gap between the flashing and the siding

Option 4)  Just caulk the gap, no metal flashing

I thought the correct answer was the second option but my contractor then caulked it.  Then in places where they “forgot” to put the flashing they said it wasn’t needed.

The area where they have a real problem is the bay window.  They cannot seem to bend the flashing around the window angles.  Is it ok to overlap the metal top flashing here?  Any tips/rules?

Also, on a couple windows they cut the flashing short of the ends which I thought was a major mistake.  He keeps saying that my house is so water tight that I shouldn’t worry about the flashing at all.

Please advise.

Thanks!

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Replies

  1. jrnbj | Aug 16, 2006 01:18am | #1

    personally, I like a real drip cap (especially with a 1x picture frame trim), but failing that, good bent metal is the minimum in my book

  2. stevent1 | Aug 16, 2006 01:43am | #2

    Our pool house has the same window details. We used aluminum flashing and a drip cap. Caulk the drip cap. We then put scotia moulding below the drip cap that covers the flashing. Some window manufacturers claim you do not need flashing because of the fins, but it is easier to do up front and you are protecting the sheathin behind the header trim.
    .

    live... work... build... better with wood

    1. BigRodent | Aug 16, 2006 03:41am | #5

      Hardie definitely says not to caulk gaps between flashing and siding... 

      http://www.jameshardie.com/homeowner/installation/hardiplank_installation.php

      I think that the housewrap says the same.   At the same time... looking at the metal flashing w/o caulk makes me think that water easily will get behind the siding.  My builder is saying that this is ok in most cases.  The house wrap is there to protect it and as long as the water has a place to go it is not a problem. 

      The top flashing is one place where there seems to be no set way to do it... 

      1. stevent1 | Aug 16, 2006 03:48am | #6

        Caulk the drip cap to the flashing, not the Hardie.live... work... build... bettter with wood

  3. User avater
    Sphere | Aug 16, 2006 02:07am | #3

    I see a few issues similar to what I am doing.

    First. "1x5" trim nets out at 3/4" I am thinking. So, the Hardie ( if lapped not sheets) is gonna be quite close to flush to the side trim faces ( jambs)...and I chose thicker trim..YMMV

    I will use a drip cap and no caulk..I hope that is right.

    so, I'd say option #2 is where we could agree.

    I dun'y know where you are or the weather extremes, but you can always ADD caulk easier than remove it.

    Spheramid Enterprises Architectural Woodworks

    "Enjoyning the finite of matter, in an infinite realm of possibilities...

  4. User avater
    Matt | Aug 16, 2006 02:25am | #4

    >>I need some opinions here. <<

     You came to the right place!!!!

    Either use metal drip cap (flashing that goes up under the siding - factory or site made) or use PVC drip cap.  IMO caulking is somewhat optional on the metal drip cap but you still have to worry about water getting in the ends unless you caulk.  PVC drip cap definitely needs to be caulked, as the lap is only about 1/4".  The PVC looks better but doesn't weather proof as well.

    As far as your option number 4, it doesn't sound like the best practice, but what about where the hardie butts to the corner board?  Same deal, so it's not like if the windows are detailed perfectly you are perfectly safe....

    The bottom line is that the caulk job needs to be checked yearly on a Hardie house. 

    My painters even caulk on the first trip for the exterior, and then re-caulk everything on the final too.  And the quality of the caulk is very important too.

    As far as the bay window - soldered flashing is the best thing, but it's a bit hard to say exactly what your situation is without a pic or something.

    Personally, I'd say your builder is no slouch if he used vicor (sp?) around the rough openings.



    Edited 8/15/2006 7:31 pm ET by Matt

  5. davidmeiland | Aug 16, 2006 04:05am | #7

    How about a version of #2?

    The Vycor would do more good applied over the top flange of the window and then lapped under the Tyvek. A metal z-flash should go over the top of the trim and under the Tyvek. Don't caulk the gap between the siding and the z-flash.

  6. Piffin | Aug 16, 2006 05:12am | #8

    he's a screwball. U B right

     

     

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