Monopoly Framed Backyard Office/Shed — Venting + Bug Screening for Corrugated Metal Siding
I am planning my backyard office (140 sq ft) that will be “monopoly framed” with no eaves (This for aesthetic reasons, city setback requirements, and HOA guidelines.)
The siding with the most visual attention will have vertical cedar board siding, but the back side I have opted for black corrugated metal for cost savings and it fits the approved aesthetic. The problem is, when mounted vertically I don’t know how to go about bug sealing and venting.
I have attached a photo of my model which shows the “crown” which will hold the polyISO foam and whose 2×10 I want to butt the top of the corrugated metal too. My questions are:
1. Can I butt the corrugated metal right up to the 2×10 and not vent at the top, but only vent at the bottom?
2. I don’t plan on furring strips for the metal siding (I do for the cedar). But I feel this complicates the bug screening. I can’t find resources on this. I will be using Cor-a-vent SV5 for the Cedar but the corrugation channels don’t work with it (obviously).
3. Off topic, but I welcome any feedback on the design. It’s come about through conversations with friends who have building experience. It’s a unique solution to a unique problem. It’s a 1/2:12 pitch so EPDM is being used and I’ll be working with a local roofing company to make metal trim as suggested in another thread: https://www.greenbuildingadvisor.com/question/epdm-roof-trim-flashing-struggles-in-the-us
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We are working on a very similar project and I am interesting in hearing people’s thoughts as this is my same concern. So far, for air flow, we have specified venting on top and bottom using perforated flashing. Because we are not using coravent or furring strips behind the corrugated siding, we are using the Benjamin Obdyke HydroGap SA Self Adhered Drainable HouseWrap as the house wrap and the Benjamin Obdyke Slicker Classic Rainscreen 6mm on top of that, then attaching the corrugated siding. The bug screen is something we have not figured out yet. I’m wondering with the other two products, if it’s necessary?
I know in places like BC, the corrugated metal installed vertically meets code as a material with a built in rain screen. Hence why I’m not using furring strips.
The bug screen is my biggest issue at the moment holding up on me pulling the trigger.
How much are you really saving by having one wall with corrugated metal?
By the time you but the brain power into working out the details of how to install the different material and acquire the fasteners, tools, accessories and clime the learning curve plus some wasted materials.
I don’t see how it is worth the effort given the small number of square feet.
Did you see the hard plastic colsure strips made to fit under the corgated steel?
Walta
Walta,
Closure strips defeat the rain-screen function of the corrugated cladding.
Noah,
I use perforated stock to over the bottom of corrugated metal cladding. It excludes all the smallest insects, which could make their way into the cavity whatever you use.
In the absence of overhangs I would omit the vent at the top of the wall as the risk of bulk water intrusion is greater than the benefit of the added ventilation it gives you.
You are fine without furring strips behind the metal panels as long as the bottom allows some air movement and drainage.
This is very clever and cost effective. Thank you very much.
Venting at the top is often seen as optional, including here on GBA. You're not getting a full stack effect through the rain screen assembly, but that would just reduce the speed of drying if you already have a decently large rain screen gap. No other rain screen benefits are affected. I did my recently completed outbuilding like that, to simplify trim/frieze details.
Walta is right; For the corrugated metal, use the foam or plastic corrugated edge closeouts sold by the metal supplier (plastic would be better for durability, generally), and put the closeouts over horizontal Cor-a-Vent strips to handle the bottom edge ventilation and the bug protection screening. Simple.
You'll need strips on that entire wall obviously, but you can use the thinner CV-3 strips if you want something slightly cheaper than CV-5 and don't already have extra material for that backside of the building. You're just padding out the gap that you already have with the metal corrugation.
I think the CV-3 strips were around $4 for a 4 foot stick when I bought them, and you aren't going to need a lot for one side of a 140 sq ft building at whatever your vertical screw spacing will be. There are also places that sell individual strips instead of a box of 24, so you can get exactly the amount you want.
Definitely a valid approach, thank you for the detail in explaining this. Much appreciated.