Rainscreen Top of wall under trim detail
I’m looking at installing a rainscreen on a wall with cedar clapboards and azek trim boards over plywood. As well as ventilating the wall, I want to ventilate the top trim (rake board and other diagonal trim with a cavity behind it). My trim is like the example on left of this https://i.pinimg.com/736x/29/02/5a/29025ad0948bfed4494c33749ecc4204–gable-overhang-figs.jpg
The azek trim isn’t very rigid so it needs support behind it, it would be very wavy with just a furring strip every so often. I have looked at the coravent system, you could use some of their SV-3s, which match the height of their furring strips, but these don’t seem to let the plywood under them breath –
https://www.cor-a-vent.com/uploaded_files/files/Tech%20Drawings%20PDF/cor-svg.pdf?1429119851523
I believe my rake boards are 1 x 10s, so you would need maybe 3 of these 3″ SV-3s.
Is there some spacer that would allow the plywood under the trim to breath as well as let air behind the trim? Some better solution to achieve that? Seems like a lot of trouble to leave the top foot+ of the wall unable to breath.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
User...522,
You are overthinking this a bit. I've used Azek trim never found it was too wavy if you back it at 16" oc. If you feel you need more, reduce the spacing of the furring strips to 12".
If y0u use Cor-a-Vent to keep out pests at the top, just use one layer and back the bottom of the Azek with plywood strips at whatever spacing you are comfortable with. Don't worry about it being impermeable. Permeable materials dry though diffusion. The plywood will dry around the Cor-a-Vent - just as it does when you use it as strapping, or at the base of walls.
thanks Malcolm,
I mention the wavy because I remember when the Azek trim was installed. It is a complex built up package of trim and the carpenters had some trouble keeping it all aligned with the full plywood backing, a little cursing going on. However, you're probably right backing doesn't need to be continuous.