How weather proof does cladding need to be?
Hi all. Building an ADU in Nova Scotia.
From the plywood sheathing out we have: Mento WRB, Vent grid (1/2″ rain screen material), 3/4″ hemlock treated with Lifetime.
The hemlock is ship lap with a 1/4″ channel, leaving a lap of 3/8″. It’s green so the expectation is that I’ll lose some of that 3/8″ lap seasonally.
I was planning on running the shiplap vertically, though now that I’m looking at the 3/8 lap and feeling how wet the boards are, I’m starting to doubt my initial plans. Realistically, running it vertically is going to introduce more bulk water behind the cladding compared with a horizontal application. My question to this group is: how much of a concern is that? We have a good, continuous drainage plane behind the siding. Should I reconsider my plans for vertical siding in order to reduce the water hitting the rain screen in the first place?
Thoughts and feedback welcome. It’s not too late to change course.
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Replies
Ry_Buc,
Cladding runs the gambit from some that are a complete answer to water intrusion, to open-cladding which lets a large percentage though to the layers behind (and is increasingly popular). Practically, where any particular one lies on the spectrum mainly affects the materials necessary for the WRB, and the diligence you need to flash and detail that layer.
Another way of looking at the spectrum is as an indicator of amount of risk you are comfortable introducing into your walls. That's largely an individual preference. I don't like intentionally introducing potential problems into my assemblies, but a good argument could be made that with a robust WRB and a rain-screen gap, the amount of risk you are proposing isn't very high.
A pretty equivocal answer I'm afraid,. Sorry I wasn't more help.
It also helps to break up long vertical runs into say 8' sections and have a z flashing back to behind the WRB. This way any water that does make it behind the cladding can be channeled out.
Make sure also to figure out all your window flashing details as there will be more exposed to water with vertical cladding.
Thanks guys. Your perspectives are helpful. I'll likely go vertical and plan differently for the house.