"Breather" between PVC and wood a good idea?

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Old 10-01-15, 11:54 AM
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"Breather" between PVC and wood a good idea?

Hello,

I have been installing PVC trim over real wood lumber in several places (for example, PVC band-board over real wood rim joists). I've wondered if I'm creating a situation where the real wood cannot "breathe" and dry out sufficiently.

Then, I just noticed in this YouTube video by ThisIsCarpentry, that they tacked a yellow, rolled material that looks a little like nylon Scruffy, between the fascia and sub-fascia. If interested, it's shown at around the 3 minute mark in this video: https://www.youtube.com/watch?v=AWK2ha2nUG0

I've seen a product called "Cedar Breather" (by Benjamin Obdyke) that seems to make sense for Cedar roofing.

I'm wondering if a similar "breather" would be recommended when installing PVC over real lumber.

Thanks in advance.
 
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Old 10-01-15, 03:04 PM
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Sounds like a bad idea. IMO all it would do is make it more likely the pvc would get wavy. We have found that solidly screwing it in pairs 12" on center works best in our climate.
 
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Old 10-01-15, 04:23 PM
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Post a picture of what your trying to cover.
A few questions, why are you not removing the old trim and replacing with PVC instead of covering it?
At the bottom of a wall if I'm understanding you there should be a piece of Z molding added under the siding and out over the trim or waters going to get behind it.
 
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Old 10-01-15, 08:08 PM
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Thanks xsleeper and Joe.
Joe, I have removed the old trim. I did find one picture that shows the PVC band-board (bottom course) and the first course of Hardie plank.
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As you can see, I did use Z-flash over the PVC. As a side-note, that Z-flash was a real problem to find. I looked all over but could not find it to cover 1x (actual 3/4") PVC. Since I don't have a brake, I ended up having to pay for custom bends.
 
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Old 10-02-15, 07:48 AM
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Did you run the house wrap all the way to the bottom of the foundation?
Did you add a kick out over that J molding so the siding would sit at an angle on top of the Z?
A simple piece of pressure treated lattis will work.
 
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Old 10-02-15, 10:28 AM
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Hi Joe.
The house-wrap runs to about 1/2" to an inch overlapping the top block of the foundation (to the bottom of the PVC band-board).
I have no J-molding. Perhaps you meant Z-mold (or flash).
As per Hardie recommendations, I ripped plank material to use as the starter strip behind the first course of Hardie plank. Although not required, I also painted the 5 unfinished sides of the starter strip.
 
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Old 10-02-15, 01:07 PM
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My typo, yes I meant Z molding.
Looks like your almost good to go.
One thing I think I see missing is no outside corners.
Should have been 5/4 trim.
All trimming needed to be done before the siding went on.
All cuts need to be sealed before installing.
I gave up long ago trying to use the Hardee trim and only use PVC.
Also what's that vent for under the window?
Hows that going to work under 4' of snow?
 
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Old 10-02-15, 01:11 PM
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My typo, yes I meant Z molding.
Looks like your almost good to go.
One thing I think I see missing is no outside corners.
Should have been 5/4 trim.
All trimming needed to be done before the siding went on.
All cuts need to be sealed before installing.
No "breather" is needed.
I gave up long ago trying to use the Hardee trim and only use PVC.
Also what's that vent for under the window?
Hows that going to work under 4' of snow?
 
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Old 10-02-15, 10:37 PM
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Joe,

I'm doing woven corners, so no corner trim is used. I know when I started planning this you recommended against the woven corners because the edges would open up over time. To attempt to counteract that, I'm using corner flash (step flash) behind each corner and pinning and back (blind) caulking.

The vent is a dryer vent. It was there when we bought the house over 20 years ago. We do enough laundry around here that the exhaust usually melts the snow before it has had a chance to pile up. There are times when I need to shovel it out, but not often enough for me to re-route the exhaust.

Thanks for your ideas.
 
 

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