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Window Drip Cap + Z flashing AFTER windows and trim installed?


tonic's Avatar
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01-10-14, 12:46 PM   #1  
Window Drip Cap + Z flashing AFTER windows and trim installed?

I have already put in a new window and exterior trim. I have appropriately tape flashed the window flanges before and after install. I didn't put any metal flashing yet.

I plan on putting a wooden drip cap above the top wooden trim piece. If I do that, is it necessary to put a metal Z flashing above the wooden drip cap that I am going to install?

 
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01-10-14, 01:54 PM   #2  
Use vinyl drip cap instead. First place that's going to peel and rot will be that cap.
I personally install aluminum Z moulding then the drip cap.
That way there's no way water can get in behind the trim or behind the siding from the top.

 
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01-10-14, 02:44 PM   #3  
Thanks Joe. Doing it your method, do you put the aluminum Z flashing under the drip cap?

And if I use a vinyl drip cap, can I skip the metal Z flashing?

 
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01-10-14, 02:55 PM   #4  
I would not skip the Z moulding, install it first.
Water can lay on the top of that small flat area on the top back side of the cap.

 
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01-10-14, 06:05 PM   #5  
So, if I am understanding you correctly. You install the aluminum Z moulding on top of the wooden top trim. Correct? Then you out the vinyl drip cap on top of that.

-or-

Or is it that you put the aluminum Z moulding on, right after the window is installed, then put on the wooden top trim and finally the vinyl drip cap?

 
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01-10-14, 06:56 PM   #6  
I would do it similar to the way it's always been done. If you are using a wooden drip cap, install the metal flashing over the wooden drip cap. If you want to skip the wooden drip cap, install a metal or vinyl z-flashing over the trim. I prefer metal. It doesn't warp when someone paints it brown and it gets up to 150F in the sun.

Then, be sure your metal flashing is behind the WRB and taped to the sheathing with window flashing tape. Skip-tape or solid-tape (depending on whether or not you want your WRB to also be an air barrier) the WRB to the metal flashing.

Canada has a code where head flashings on windows and such need to be UPTURNED 1" on each end, then the siding is slit to allow it to slide down over the upturned ends.

No such code here in the US, but it's a good way to prevent water from running off the ends of the flashing and getting behind the siding. Can't say that most contractors want to take the time to do that sort of thing.

 
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01-14-14, 04:20 AM   #7  
Thanks guys. I think I'm going to try to be more conventional and install the metal Z flashing above the drip cap.

XSleeper, I understand what you are saying about making sure to tape down the top part of the Z flashing and tuck it under the siding directly above it. Here's my problem... How am I supposed to tape down the flashing down unless I remove the siding to begin with?

If water gets behind the siding, and the Z flashing which should be behind the siding isn't taped down, then water could potentially get behind the Z flashing. Correct? Wouldn't this mean that all the time and effort to install Z flashing isn't as worthwhile?

 
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01-14-14, 04:42 AM   #8  
If the siding is already on, don't worry about it.

 
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01-15-14, 08:58 AM   #9  
Thanks for the tips guys. One last thing...

How much longer than the top wooden trim piece does the vinyl drip cap need to be? I was thinking like 1" on both sides or something. What do you guys do?

And if I decide to put metal Z flashing above the drip cap, does the metal flashing also have to be wider than the drip cap directly underneath it? By how much?

 
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