How to attach vertical siding with a rain screen?
BillWolpert
| Posted in Green Building Techniques on
Is there a ventilated furring strip for vertical wood siding? Or, are there clips available? How does a horizontal furring strip not interfere with air circulation when incorporating a rain screen?
This project is in Climate Zone 3C.
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Replies
You could leave offset gaps in the strapping, e.g. straps only span two studs, and alternating straps drop down a few inches. Not ideal for air flow, but may be sufficient. A better solution might be two layers of strapping, vertical and then horizontal.
Bill,
You have two choices:
1. You can just install horizontal furring strips (and stop worrying about drainage) -- an approach that gives you most, but not all, of the advantages of a rainscreen gap, or
2. You can install two layers of furring strips: the first vertical, and the second horizontal. (Lots of Passive House builders take this approach -- for example, it was used by Alex Carver at the "House in the Woods" project described in my recent article, Three Superinsulated Houses in Vermont.)
For more information on this topic, see All About Rainscreens.
-- Martin Holladay
If you are concerned about it, and I'm not sure how much you need to be (even though, as you say, there would be SOME reduction in circulation and drying), you could cut shallow kerfs on the back side with a circular saw or a router.
Here's some more detail on the two layers of furring approach if that's of interest: https://hammerandhand.com/best-practices/manual/4-rain-screens/4-6-horizontal-rain-screen-battens-vertical-siding/
Also consider "Slicker Classic" or other mesh rain screens. Or DrainWrap with horizontal furring over it.
Rain Screen products such as Gravity Cavity or Sure Cavity would do the trick - less labor than the furring approach. Another angle is to use a nailer on top of a drainage strip like Corrugated Lath Strip to create the drainage gap. See attached - more info at https://www.mtidry.com/products/accessories-and-miscellaneous/corrugated-lath-strip
Two other possibilities come to mind. CoraVent Sturdi Batten (http://www.cor-a-vent.com/sturdi-battens.cfm and ) and Coroplast corrugated plastic sheets (http://www.professionalplastics.com/COROPLASTSHEET or https://www.wholesaleartsframes.com/10mm-3-8-corrugated-plastic-sheets/). The latter would need to be cut into strips, but I spotted it on GBA here https://www.greenbuildingadvisor.com/blogs/dept/musings/all-about-rainscreens
and here https://www.greenbuildingadvisor.com/community/forum/green-products-and-materials/12494/i-am-searching-plastic-shimming-product-providing
and here https://www.greenbuildingadvisor.com/articles/dept/musings/these-superinsulated-homes-were-delivered-truck.
Tyler and Bill Deitze,
I agree. Unless you are using a siding like corrugated galvalum which can span more than 24" between supports, building a rain screen with both vertical and horizontal wood battens becomes pretty labour intensive. Dispensing with the vertical layer and using one of the proprietary drainage products you have linked to makes more sense.
Thanks for everyone's insights.
diagonal furring strips (45*)?
Old thread I know, but has anyone tried just cutting like 3.5" x6" blocks of plywood and screw through those into each stud with the horizontal furring over that. Not drastically different than 2 layers of furring, but seems like less material (furring and screws) and less effort.
Connor,
Don't see why it wouldn't work. The resulting cavity would be a lot more effective too, with the air being able to move in all directions unimpeded. I'm surprised someone doesn't sell pre-made stand off blocks for that use.
One advantage of using vertical strips as your primary layer is that as long as the sheathing is 1/2" or thicker, you don't have to hit the studs.