Polymer Siding
We’re planning a 1200 sf addition on to a small brick ranch in zone 5. The plan is for 2 x 6 on 24″ centers with dense pack cellulose insulation followed by zip system sheathing then 2″ of rigid foam, probably polyiso. We want to side it with Certainteed’s polymer siding in the double seven rough shake style. I’ve read Scott Gibson’s post and other commentary regarding the attachment of vinyl siding and I’ve spoken with Certainteed. Normally I would think that furring strips would work but this particular style is odd that it comes 57″ long and obviously not going to work on a normal layout. I’m thinking the solution to this to add a layer of sheathing over the foam and then a WRB but I’d appreciate any thoughts or feedback. By the way, Certainteed won’t honor any warranty for this product being installed directly over foam thicker than 1″.
Thanks ahead of time,
Skip Ward
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Replies
You could switch to a 2X4 wall, which would only require R-5 to be moisture safe in your climate zone. I'm not sure if you would have to reduce the spacing between studs, however. If that approach isn't appealing, I imagine you could use ZIP-R.
See this article for more detail. https://www.greenbuildingadvisor.com/blogs/dept/musings/calculating-minimum-thickness-rigid-foam-sheathing
Skip,
Steve's two suggestions make sense. Or you could just choose a different siding.
-- Martin Holladay
If you are going to have a continuous layer of cold wood sheathing (preferably plywood) to support the siding, then you might as well consider putting foam (edge strips or continuous) on the inside.
Gentlemen,
Thanks for your responses. Steve, at the risk of coming across uninformed, I assume your suggestions are for cost and material saving right? I mean if I proceed the way I proposed it won't be enhancing moisture problems will it?
Martin, after much deliberation, hand-wringing and grinding of teeth, the Czarina decided on this siding and I don't know if there's any turning back that wouldn't involve a lawyer.
Jon R, yes, the thought was to use plywood over the foam but again being naive I'm not sure what you mean by edge strips