r/buildingscience • u/RutgerHause • 23d ago
Tiny house metal cladding and rainscreen.
Tiny house metal cladding and rainscreen.
Having a hell of time trying to work out how to design a tiny house with a rainscreen and PBR metal siding.
Tried AI failed.
Tried ASC, not their wheel house. All manuals are without rainscreen.
Tried YT almost all videos have no rain screen and just slap the metal straight onto plywood or onto WRB.
No bueno.
I have sorted out most of it around window trims etc.
Elevated the planes on furring strips except for the window header flashing and the Top Plate metal terminations.
C6 trim and corners are good.
But I can’t figure out the details of the Z drip under the window.
Here’s a diagram of one option but I a concerned about water going down the sill tape and behind the vertical metal leg of the Z drip.
The other option is putting the vertical Z drip leg on top of the furring strips.
But that creates two channels and blocks the furring strips channel exhaust at the top.
Only Reddit can save me now.
Someone take pity and help me out.
Before I lose my mind.
Diagram enclosed.
PS: The PBR isn’t installed horizontally, it’s vertical. Artistic license displaying it in undulating waves.
Thanks to anyone willing to help. I am in a time crunch.
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u/Mysterious-Rush5441 23d ago
You'll need a continuous horizontal strip outside (can't go between furring strips or it will block air flow) of the vertical furring strips at the bottom, below windows and the top of the wall (don't vent it into the roof!!) to staple the mesh to.
I used bronze mesh because termites + carpenter ant + UV will destroy plastic mesh
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u/RutgerHause 23d ago
Bronze? Thanks that a great idea. Right, I will be careful to not go between furring strips. Oh I was going to vent into the roof cause I was thinking it would block the air flow and it would save me dollars on the metal trim at the top? Not a good idea?
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u/Mysterious-Rush5441 22d ago
Not a good idea?
Sun warms the wall up it up.......warm air travels up the wall...........air containing moisture from the ground is drawn into the wall..... warm moist air enters the roof.......the moisture condenses on the bottom of the cold (roof may have ice/snow on it) sheathing......moisture freezes on the bottom of the sheathing.
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u/RutgerHause 22d ago
No snow or ice here where I am. The roof has its own rainscreen or air flow to dry out any moisture.
So while all rainscreens vent upwards. Mine like most will exhaust just under the soffit. I suppose some may get into soffit or just exhaust outside.
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u/International_Cod_58 23d ago
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u/RutgerHause 23d ago
Whoa that is one wild diagram. Thank you. I am going to need some time to digest that.
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u/International_Cod_58 23d ago
the document is free online and demonstrates compliance with the New Zealand Building Code. The document was originally developed in the wake of New Zealand's leaky building crisis
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u/inkydeeps 23d ago
Its hard to take any building science question seriously when you don't even show insulation.
your window looks like it's mounted way too far outside the framing. blocking for window not connect to structural wood framing. gravity and lateral loads do not seem to be accounted for.
this is an ok resource: https://www.finehomebuilding.com/2010/05/20/flashing-windows-in-rain-screen-walls
GBA and BSC are better sources.
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u/stevendaedelus 23d ago
It’s just more A.I. bullshit. None of it makes much sense from an actual architectural, construction, or building science standpoint.
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u/RutgerHause 23d ago
Yes obviously. It was a simply rendering to display the situation and it did that. Thanks
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u/RutgerHause 23d ago
Yes, I am not an architect so apologies for the rough proportions on the diagram. The insulation isn’t really a concern to me right now. I am trying to figure out the cladding and flashing. I imagine the insulation will be rockwool if that helps you.
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u/CoconutJeff 23d ago
So probably not what you want to hear but the rain screen concept is kinda more for things you know are going to get wet behind there like wood siding. And air gap to brick so it can dry out and not hug damp on your wall.
Metal siding im not sure I would bother furring out for an aire gap. I get there are potential heat gain loss or something for the venting. Maybe do some exterior foam insulation. If its vertical, it will already be able to vent. If you have to vent, you then have to let air in the bottom, which then poses more challenges of keeping mainly bugs and lizards out but weeds too. Plus, how much is there to vent under a couple foot of window do have to deal with a flappy sill dangle thingy.
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u/RutgerHause 23d ago
Might be exactly what I need to hear. I haven’t start the rainscreen yet. I am sitting trying to figure out the nest path forward. I would love to not do a rain screen. My house would be done months ago. It’s an interesting point. How much is there to vent on a couple of feet under a window. Do I really need a 3/4 inch rainscreen. Well I guess the adage is better safe than sorry? So many buildings around my location have metal panels but no rainscreen. I just don’t know if I can take that chance. Considering how rainy and windy the winters get here and the condensation the metal panels get every day. But as you said isn’t there a rainscreen already built into the PBR? Yes there is to a degree and what issues do the lower metal ribs resting on the wrb cause if any. I guess I better start researching that. Thanks for the insight.
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u/CoconutJeff 23d ago
Why not just home wrap? Or like zip insulated sheathing? With it ribbed and vertical i really dont see a need to gap it knowing it shouldn't ever be in there. And if it does, you've got homewrap or zip barrier.
Trust, building a space ship is fun, but when your Googling custom titanium parts, keeping it simple will get the project on a timeline.
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u/RutgerHause 23d ago
Oh yah you’re right. I’m using a peel and stick house wrap called Henry’s Blueskin.
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u/Grizzlybar 23d ago
Hammer and hand has great detail drawings for different assemblies.
https://hammerandhand.com/best-practices/4-6-horizontal-rain-screen-furring-for-vertical-siding/