Unconventional siding: corrugated metal + Roofing slate
Our house is sheathed with conventional 0.5″ plywood, and now we are deciding on siding.
The first layer will be “JumboTex” to serve as a WRB. Beyond that, we are considering using corrugated metal sheets installed vertically as a rain screen and then siding with used, natural roofing slate tiles.
Why? Well, we have all the materials available in abundance from an old barn and a dismantled house. There are also evident benefits in durability, maintenance, and aesthetics.
My question is whether there are pitfalls to this idea. I have searched for similar assemblies on line but have found very little that is comparable. For example, is this an adquate rain screen? Would the facade be too fragile? Heat buildup behind the slate? Wind noise? Excessive weight?
The studs are true 4×4 less than 16″ on center, so the house is very strong. We plan to use GRK *cabinet* screws of various lengths for all of the siding work, except the WRB of course. This is also unconventional, but their wide heads and T-15 head work exceptionally well for fastening corrugated metal and other thin materials.
Comments appreciated.
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Hey Eric,
I haven't seen much slate siding. But there is a link below to one house that has slate as the siding at a covered entryway. Perhaps the architects who did that project could be a resource for you. Or you could consult an engineer.
Slate is super-heavy. I spoke with another architect about a house with a slate roof recently and he told me that slate roofing essentially doubles the dead load of the assembly. Common roof assemblies with sheathing and asphalt or metal roofing have a dead load of about 12 lbs. per sq. ft., he said. Depending on their thickness, slate tiles alone can have a load of 12 lbs. per sq. ft. The architect I spoke with consulted with an engineer for his project.
Here's the project with the slate siding:
http://reversearchitecture.com/project.html?name=Zigzag%20House
Eric,
I don't think there is a problem with slate as siding, but I'm unsure of the best way to detail it. Because it is a reservoir cladding you will want a fairy low perm WRB, and a gap between it and the slate. There are siding companies who do install it. Maybe they can supply specifications.
https://www.greenstoneslate.com/stone-cladding-slate-siding/
Corrugated metal siding gets used a lot here, mostly relying on the shape to form a rain-screen, although some builders also install it on horizontal battens. I've never seen cabinet screws used. You need a gasketted head screw to make it waterproof.
Edit: I missed that you were suggesting using the metal siding as an underlayment. That's not a good idea. Find out how slate is typically installed and do that. I wouldn't start making up something.
Air sealing is always important. So tape your plywood and then test with a blower door.
Do research support requirements. Consider not using the steel. My guess is that slate is naturally well enough ventilated that it would be fine with a low perm (eg, 10-20 wet perms like HydroWrap) drainage WRB and no additional air gap. Or furring. Either would be far more common (ie, easy to verify that support is adequate).