T1-11 vs Coravent Rainscreen
Hey All,
For a new construction in CZ6, we will be using vertical wood siding as cladding. The stackup will be R23 rockwool in a 2×6 cavity > 7/16 zip > 2″ reclaimed polyiso > rainscreen > vertical wood cladding. Windows will be flashed at the zip layer.
Thinking though the best rainscreen for that cladding….
I know that coravent makes a great rainscreen, but not sure how well it would work over the CI foam layer. Maybe it makes no difference, or maybe the siding needs something a bit more sturdy to hold on to.
The other option that seems to work for vertical siding is rips of T1-11 siding, turned backwards so that water can drip through and air can move up and down and dry things out. Both options would have a bug screen at the top and bottom.
Pros and cons of either of these two options given the details? Anything to be weary of?
Thanks —
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Are you planing on using 4" screws to hold the siding on, or what? Assuming you 'd be using 3/4 siding and 1/2" furring, you have 3.25" of thickness to get thru to the sheathing. I use a siding nail gun with stainless nails for my vertical siding and the longest nails you can get for those is 2.5". Framing nails go to what, 3.5"? The OSB/Zip makes me a little nervous on nail hold too, especially with 3" of soft material in front, and if you are using green siding. Screws would take forever, but maybe work in osb?
You definitely can't attach siding directly to the Coravent. I would be nervous attaching it to the T1-11 too, especially if you are using 24 OC framing. As the siding dries (if green) it's going to want to move around. I think you want some stiffness in whatever it's attached to.
I can tell you what has worked for me. 1/2 ply sheathing. no exterior insulation. 1/2" ply furring with a bevel on the top edge. Vertical green hemlock shiplap installed with 1.75" stainless ring shank nails. The wood shrinks after it's put up and creates drain/ ventilation paths.
Take this with a grain of salt cause I'm not a pro, but If I was building with exterior insulation & vertical siding, I would probably use 16 OC framing, 1x4 for furring with a shim behind to create a drainage gap. Furring fastened to studs. Windows on bucks. Attach to siding to the furring only. Or 24 OC with 2x4 furring.
Thanks for the notes. Definitely rules out coravent which is what I suspected, and still raises some concerns on having too much layer thickness to have to manage with normal nails in guns.
I've also been debating a bonfig wall to bring the additional depth to the interior and allow the use of R30 batts. It has it's own host of considerations and challenges, but may be the smarter option in this case with the vertical siding.
You can use regular wood furring strips installed at an angle (not horizontal, but not vertical either). You would probably also be okay just installing them horizontally, the most recent FHB podcast had some discussion on this. It is very unlikely there would be enough bulk water to pool up on the top edge of the horizontal furring strip, the main purpose is vapor drying and it would still allow for that.
Very little water should make its way to the WRB so you shouldn't have to worry too much about drainage. It's good to allow for air flow but what I've done a few times now is stapled rips of Slicker Classic (or other spun-bonded rain screen material) to the back of the furring strips before installing them.
I really like that idea Michael. I did listen to the latest FHB about a lack of concern over going horizontal with furring.... but it feels even better to have some means of exit for any water to get out of there if needed. Assuming you're using standard 1x4 for furring?
Yeah. We found that it compressed into polyiso but still maintained a gap.
Wow, this is such a simple solution... Sounds WAY easier and cheaper than vertical siding + horizontal furring + vertical furring.
Wish I'd thought of this a couple years ago.