Nailing Utility Trim Under Window For Vinyl - Windows, Siding and Doors - Contractor Talk

Nailing Utility Trim Under Window For Vinyl

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Old 07-16-2012, 05:30 AM   #1
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Nailing Utility Trim Under Window For Vinyl

So, I just rehabbed a dormer that had a lot of bad flashing issues/ 25 year old vinyl and two layers of roofing. Roof replaced, step replaced, siding replaced, everything nice. Then I replaced the window with a new construction vinyl with J channel built in. Double 4" vinyl siding going on later. I flashed the window with flashmate sticky tape on the bottom before window went in, then cualked sides and top of back of flange, set window, nailed and taped sides and top of window flange with the flashmate.

Question is, when I went to install the siding, I wanted to use my new shiny snap lock tool and utility trim under the window for the piece of siding that got the nailing flange cut off, and I had to nail the utility trim under the window through the flange and flashing. I didn't like doing it, but I only put a few nails toward the center, trying to stay away from the side corners. I figured the flashmate will hopefully seal against the nails like I/W. Is that how the real siding guys do it when using a window like this?
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Old 07-16-2012, 12:07 PM   #2
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Re: Nailing Utility Trim Under Window For Vinyl

I always nailed vinyl sill/utility trim under and over windows and over doors over lath after channeling was installed and made sure to allow for expansion and contraction when nailing. Snap locked siding into sill/utility trim which always left a nice finished look and never once had a problem.


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Old 07-16-2012, 01:49 PM   #3
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Re: Nailing Utility Trim Under Window For Vinyl

if your worried about nailing up so high you could take a strip of aluminum say 3'' wide,slide it all the way in to the u/t

that will effectively extend the nailing flange about an inch and a half lower

the cut in the siding panel will control side to side movement

i don't bother with snap locking window cuts 3'and under
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Old 07-16-2012, 05:25 PM   #4
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Re: Nailing Utility Trim Under Window For Vinyl

For most windows we snap the undersill on the siding panel before install. IOW, no nails into the flashing tape. Make sure to place a nail close to the window on either side and I'm assuming that you would never put a seam directly under a window.

Related, you will find an excellent flashing detail in the JLC Field Guide for the J channel sides pieces.

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