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Discussion Starter · #1 ·
Search gives no answer, so I have to assume that the question is so dumb no one thinks it needs to be asked.

New construction vinyl windows with integral nailing fin, with a 5/4x4 Azek trim (Hardi plank siding). Should the aluminum drip flash go on top of the window, with the vertical leg up under the Azek trim, OR should the drip flash go over the trim?

My head says the trim should be directly over the window to ensure water is directed out, but I can't see how water sheeting down the exterior of the siding wouldn't go behind the trim. Do you flash both locations?
 

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I flash all my windows with self adherring membrane, Grace Perm-a-barrier. I use Anderson Windows so they have a nailing flanges. Then I trim the windows with AZEK and put a drip cap on top of the AZEK. The AZEK should be relatively tight to the window frame and any gap gets caulked. If the caulk fails you still have the flashing around the window. Just make sure the housewrap goes on top of the flange of the drip cap
 

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Curmudgeon
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Discussion Starter · #6 ·
Thanks guys. Tinner, I looked at your site previously - good notes for future job sites. Sadly, I see much of the same stuff here. Shingle-style installation doesn't seem too important to some. We do live in a semi-arid climate, but when it rains - well, you know.

Neo - had reviewed that article as well, and have already been performing those steps for years. The house I am working on now is the first time I will be installing trim (1x4 or similar) around the windows. Typical new home construction here is just flash as per builder's norm (some good, some not so), head flashing over the vinyl window, and stucco.

I had been thinking about 2 flashings with this installation, but hadn't committed because I can get a little too anal.

Why use a z-flash over the trim - why not two drips?
 

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I use lead coated copper for my drip caps and 2 will not look right. 5/4 PVC trim comes out almost flush with the window so if you have a drip cap above the pvc how will water get in if you caulk the window to the PVC trim. I use flashing because I never rely strictly on caulking.
 

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Curmudgeon
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......I had been thinking about 2 flashings with this installation, but hadn't committed because I can get a little too anal.

Why use a z-flash over the trim - why not two drips?
Looks cleaner, and serves the purpose. :thumbsup:
 

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not a big fan of trim that projects flush with the window,i usually like to pack it out so the trim is proud of the window at least 3/8''

id put the flashing ontop of the trim and the unit unless the window has an intergral fin like an andersen casement i really dont consider tape a flashing
 

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not a big fan of trim that projects flush with the window,i usually like to pack it out so the trim is proud of the window at least 3/8''


I`m with Tom on this one. I never leave head trim flush with window I always have a larger head trim for extra protection :thumbsup:
 

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Discussion Starter · #11 ·
Ok, time for another question that I can't find an answer to. (by the bye, I have Windows & Doors, and Exterior Finishes, both by FHB - neither addresses either question)

The original look for the houses in this neighbourhood had traditional sloping sills, with horns, projecting 1 or 1 1/2 inches. I have seen modern vinyl windows with a trim under which replicates this look. Question is, the vinyl window has an integral drip on its sill which is defeated by having a projecting trim underneath - how do you create that trim without creating a seam which will allow water sheeting off the window to be driven back into the wall?
 

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I use lead coated copper for my drip caps and 2 will not look right. 5/4 PVC trim comes out almost flush with the window so if you have a drip cap above the pvc how will water get in if you caulk the window to the PVC trim. I use flashing because I never rely strictly on caulking.
Caulking shouldn't be on the top of any window. If water does get in, it cannot get out.

Aside from that, I like your method. If it's on a gable though, I would put some flat metal under the trim board down over the top of the window itself, along with the tape to seal the nails that are in the trim board.
 

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Ok, time for another question that I can't find an answer to. (by the bye, I have Windows & Doors, and Exterior Finishes, both by FHB - neither addresses either question)

The original look for the houses in this neighbourhood had traditional sloping sills, with horns, projecting 1 or 1 1/2 inches. I have seen modern vinyl windows with a trim under which replicates this look. Question is, the vinyl window has an integral drip on its sill which is defeated by having a projecting trim underneath - how do you create that trim without creating a seam which will allow water sheeting off the window to be driven back into the wall?
They use caulking, plastic weld, or a bend in the vinyl. Not sure how you would replicate that without using simple caulking to keep the water out.
 

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a vinyl window with a drip groove? i don't think ive seen them

just to clarify i would use a z flashing ontop of any window without an intregal fin and a projecting drip on the trim
 

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topsail's trimcat
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i typically run vycor or blueskin along the nailing flange atleast 6" rolls, then back caulk the header trim along edges and top, then back caulk the metal drip edge thats bent and run vycor over the back section of the dripedge that is up against the wall
 

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Al Smith
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I'm assuming these vinyl windows with nailing fin don't have an integral J channel? If they do the drip woulg go on top of the azek with flashing behind the bottom sill nailing fin directing water over the next lower full siding course.

if no J a zee on top of the azek with a drip cap over the window, this metal dip cap should project beyond the window to the full width of the azek head over the exterior azek lineal casing
 

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solar guy
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not a big fan of trim that projects flush with the window,i usually like to pack it out so the trim is proud of the window at least 3/8''

id put the flashing ontop of the trim and the unit unless the window has an intergral fin like an andersen casement i really dont consider tape a flashing
Do you do this at the sill detail too?
 
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