Rainscreen for corrugated siding?
Emel
| Posted in General Questions on
We are planning to use corrugated metal siding over the Benjamin 6mm Obdyke slicker rainscreen, which will be placed over Benjamin Obydke hydro gap for house wrap.
My question is, because metal doesn’t breathe, will the corrugated siding combined with the other two products be enough to not only allow water to drain but also airflow for drying? I read in another post that using perforated flashing in place of the normal flashing at the bottom should allow the needed airflow, but wouldn’t that allow water to drip down the side of the house and negate the flashing’s purpose?
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Replies
The spun-bonded rain screen product will allow for drainage and for a tiny amount of air flow, but not enough air flow to do much. I would be stringent about air-sealing and if you're in a cool climate, I'd add a variable perm membrane at the interior to be safe. Or I'd use a more robust rain screen.
Thank you. Would something like coravent work well?
Yes.
Vertically installed corrugated is self venting. As long as you install perforated closure on the bottom, you don't need anything else.
If it is horizontal install, I think your dollars are much better spent strapping out the wall and building a standard rain screen.
Although the metal is vapor impermeable it is near impossible to install it in air tight manner. Especially if vented, it will dry just fine.
Very little water should make it behind your siding, if you see water dripping out the bottom a flashing detail has failed.
Thank you Akos! That makes sense. The part of the wave in the corrugated that would touch the house wrap, would that be an issue or what I think I’m understanding is that the 7/8” protruding waves would be enough to vent for everything even though the other is flat against the house? And forgive me if this is an ignorant question, would perforated flashing at the bottom negate the ability to kick water out and away from the home? Would it just end up drip down the foundation?
Emil,
It's a good idea to include a drainage path for moisture on rain-screen cavities, but if enough water is accumulating behind the siding that it actually needs to drain as opposed to diffuse, something has gone wrong with the wall.
The only situation where the perforated base flashing is a problem is where there is another siding type below. In that case I call out a second solid J-flashing 1" below the perforated.
Good point. I was thinking of V-rib panels, which allow a tiny amount of venting, but far less than true corrugated panels.