Rainscreen idea for vertical cedar siding
Hello,
I haven’t posted a question in a while mostly because I have been building my workshop (Idaho-Zone 6-annual rainfall 20″). It’s been a long road… a timber frame I cut myself and enclosed with SIPs. I opted for a cold roof assembly and SIGA membranes all around ($$$$). I’m about ready to start the siding and I’ve been thinking about my options (for a loooong time). I could do (1) Coravent SV3 furring strips run horizontally, (2) furring strips run diagonally with Coravent SV3 at the top and bottom, (3) a 3d rainscreen… Then I had an epiphany. What if bought a roll of HomeSlicker, cut strips and basically stapled these strips to the back of strips of 7/16″ CDX? Then just screw the CDX to the WRB? The assembly would give a better nailing/screwing surface than the Coravent SV3 (7/16″ + 7/16″ OSB) and still provide airflow and drainage vertically. Does this sound reasonable?
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Replies
John,
It would probably work, but the approach is very labor-intensive.
I'd be concerned about direct contact, surface to surface of the Cedar to the CDX. I'd go with the Cor-a-vent Strips and screws into the outer layer of OSB on the SIPs as your main attachment with your preferred WRB over the SIPs.
I am working on a similar building. I considered furring strips in a herringbone pattern. Spent a bit of time trying to figure it out and lost my patience. (I also wanted my nailing pattern tidy.) I went with the horizontal coravent option which I like. It did require blocking, lots of that.
It should perform fine. I'm not sure the HomeSlicker will provide for enough free air movement for the assembly to be considered truly "ventilated" (compared to coravent), but it probably has drying advantages over Homeslicker without an air gap. Whether that is worth the extra effort is up to you.
John,
That is the basic concept behind the detail below, but the strips are already cut to strip size. The product is called Corrugated Lath Strip by MTI, and it works behind all types of siding. Dr. Joe Lstiburek mentions in his latest article that a 3/16" gap is appropriate behind siding (at https://www.buildingscience.com/documents/building-science-insights/bsi-111-double-play).
Product info at https://www.mtidry.com/products/accessories-and-miscellaneous/corrugated-lath-strip
Tyler
I saw that product at the recent JLC Live in Providence. It seems like a great idea. Have you used them Tyler? What was your experience?
Given that you are in a relatively arid climate, I don't think the depth of your vent space is all that critical. The fact that you have any space at all would be adequate or even best practice for your situation.
Peter