Rainscreen - vertical (corrugated) metal siding

[bac4uw]

I am considering using sheet metal panels (galvalume corrugated) installed vertically as siding for our small cabin project. I'm in an area where we get lots of precipitation (90+ inches per year, mostly rain). My next/last exterior project before winter is to install siding and, given the local conditions, it is highly recommended that I include a rainscreen in between the exterior siding and cabin structure/OSB sheathing. The cabin is currently wrapped in Tyvek, with OSB panels over 2x6 studs frame 16"oc (ish).

I am considering my options on rainscreen construction and am seeking out opinions. My preference is to have the rainscreen cavity extend no more than 3/4" from the structure. Stock metal panels seem to come in widths where the ideal screw placement might not align well with the studs / vertical rainscreen strips. (e.g. a 36" panel is 4 inches wider than the span of two studs, or worse - there are 25.75" stock panels where the overlap lies exactly in between studs). It seems that one approach for vertical siding is to install vertical furring strips and then install horizontal strips over the top so you have a consistent surface to screw into. Alternatively, there are some expensive products out there that can be overlaid on the entire structure. Another alternative is to cut wider furring strips that align with the overlap and would provide a stable connection. Any other options or opinions on how to approach this?

(Project here: http://countryplans.com/smf/index.php?topic=14205.0)

[NathanS]

From the reading I've done, it seems like vertical and then horizontal. If one of those specialty products is stocked locally, you could at least look at pricing. But yeah, I know the mesh stuff that you can put on behind wood shingles is really expensive.

I've also seen/heard of a PVC type furring strip that has notches in it, so you can just do the horizontal and skip doing vertical first.

[ChugiakTinkerer]

If you have the tools and the time you could probably fashion a decent horizontal furring strip out of wood 1x2 (or whatever appropriate dimension) to emulate the PVC thingy.  Using a  table saw with dado blade set to no more than 0.25" you could put a lot of grooves in the furring boards.  Nail them horizontally to the cabin; the grooves would be oriented vertically against the cabin wall and would allow water to drain.  You could space the grooves about every 6" or so, maybe even closer.  You reckon that could work?

Edit: Or save the time and get the product Nathan mentioned.  Something like this: http://www.cor-a-vent.com/sturdi-battens.cfm or http://www.cor-a-vent.com/sturdi-strips.cfm

[Don_P]

I'm thinking the vertical corrugated is creating a vented rainscreen by itself.

[bac4uw]

I'm thinking the vertical corrugated is creating a vented rainscreen by itself.

I thought the same thing. I read somewhere that it may be sufficient in and of itself without additional furring... I've read other places that suggest you should still try to get the corrugated siding off of a Tyvek vapor barrier. This is probably an issue I'm overthinking.

My latest thought has been to staple doubled over 30# felt strips vertically (I have a lot of leftover felt). This should give me 1/8" off of the structure to then nail/screw 3/8" plywood strips horizontally... yielding a 1/2" rainscreen that doesn't have a continuous horizontal block. Chugiak -- this might be slightly less work?

I've been looking for the cor-a-vent... first two places I contacted on their dealer list didn't actually have access to it. I priced a slightly different product out and it was about $600 for the surface area I was considering... which has turned me off to seeking out a product for this purpose.

[Don_P]

Cold metal and intaking damp air does concern me. I'd be tempted to put a humidity data logger inside the assembly somewhere.

[ChugiakTinkerer]

I thought the same thing. I read somewhere that it may be sufficient in and of itself without additional furring... I've read other places that suggest you should still try to get the corrugated siding off of a Tyvek vapor barrier. This is probably an issue I'm overthinking.

My latest thought has been to staple doubled over 30# felt strips vertically (I have a lot of leftover felt). This should give me 1/8" off of the structure to then nail/screw 3/8" plywood strips horizontally... yielding a 1/2" rainscreen that doesn't have a continuous horizontal block. Chugiak -- this might be slightly less work?

I've been looking for the cor-a-vent... first two places I contacted on their dealer list didn't actually have access to it. I priced a slightly different product out and it was about $600 for the surface area I was considering... which has turned me off to seeking out a product for this purpose.

That sounds like a workable solution.  The felt will just be a standoff.  The 3/8 plywood strips will have a lot of flex though, so you would want to have the felt strips pretty close together.  You might as well give it a shot.  Put up some felt strips and plywood furring and attach a panel or two.  See if that gives you enough rigidity.  If not, you could decrease the felt strip spacing and/or go with thicker plywood.  I would have no concerns about water drainage, and using felt is a bonus too as this is what it's made for.

Closing thought - Whatever you use to attach the siding will probably go through the plywood and penetrate the sheathing.  If that is the case you want felt behind the plywood at every screw.  If screw won't penetrate the sheathing then it probably isn't needed as frequently.

[busted knuckles]

I saw online, somewhere, where they used the dimpled barrier to keep water out of basements, as a rain screen. You may not want to cover the whole building with it, just cut it into strips. Make sure screws are long enough to go through it to the sheathing. Also make sure its facing the right way.