Material for rainscreen bug screen
Trevor_Lambert
| Posted in General Questions on
I was going to use aluminum screen to cover the gap at the bottom of the rainscreen, because it stands up better than fiberglass screen in standard use. Now I’m second guessing that, because the screen is going to be protected from UV, wind, and mechanical damage. It would be a lot easier to work with. Am I right in thinking it will be durable enough?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Dunno. I used Cor-a-Vent vent between furring strips and around windows, behind trim.
Trevor,
The problem with using any bug screen is that the most common cause of damage is weeds growing up into the cavity, which tear the screening when they are pulled out - and that screening is inaccessible for repairs without removing the cladding that covers it. I prefer to use perforated stock, which is easier here on Vancoiuver Island as all the lumberyards stock it.
I'm not concerned with weeds. There will be a drip cap underneath the screen, plus I'll have landscape fabric and gravel around the building. I haven't seen that perforated stock around here. How big are the holes? From the diagram it looks like bugs could go through them.
Trevor,
Without the risk of weeds you are fine with either type of screen. The holes are sufficiently small to stop pests except for the small red ants that get into your cavity no matter what you use.
Aluminum screen does *not* hold up well when exposed to wet organic residue. That means the damp gunk and critter bodies that always seem to accumulate near this stuff will rot out the aluminum screen in less time than you'd expect.
I would use stainless steel screen, 304 or 316 alloy, 1/16" mesh. Get welded wire (instead of woven) if you can. You'll probably need to order this in, but it is available and it will hold up well over time.
BTW, I would have no issue using Malcolm's perforated metal strip if you can find that.
Bill
I'll probably end up using this.
https://www.metalsupermarkets.com/product/stainless-steel-perforated-sheet-304/
Trevor,
I've used that as soffit vents interspersed with cedar channel siding.
22 gauge will be fine, no need for anything heavier than that.
Note that you'll need a bending brake and a shear to form it, and I mean a proper sheet metal shear -- something that can at least cut the 4' width of the sheet -- not a hand tool. Metal fab shops should have that stuff.
BTW, if the fab shops have both "box and pan" and "press" brakes, you'll probably get a better finish on the outside of the corners if you have them use the "box and pan" brake. Press brakes can sometimes make marks that look like scrapes when pressing the piece into the lower forming die.
Bill
They don't stock it in 22ga, that would be the only reason. I was actually thinking that I'd use a flat strip and screw it to the bottoms of the vertical strapping.
It won't be very secure that way. You would be much better off having a lip formed on either side to make a small C channel. If you use it flat, it will bow out between supports unless you use pretty thick material for the stainless sheet unless you supports are pretty close together.
Bill
Bill,
This is the profile they stock in all our lumberyards. Comes in a variety of widths.
https://www.menzies-metal.com/metal-flashings/perforated-j-channel-rain-screen-low-back/
You put it up first, then just slide the strapping into it.
It would be secured from the bottom every 2 feet, and along one edge (the outer, horizontal strapping) the entire length. I could add a blocking piece in between to reduce the span to 1 foot. Folding the material to a U profile will at least quadruple the price to something like $10 per foot.
The stuff Malcom linked to is aluminum. Is that ok because it's more substantial than screen?
Trevor,
It's available in either aluminum or galvanized at Menzies and other suppliers.
https://www.menzies-metal.com/wp-content/uploads/2019/02/Perforated-Rain-Screen-V4-010621.pdf?v=1750441228
https://precisionmetals.ca/inventory/rain-screen-j-flashing/
If you do use stainless screen, there are suppliers that sell in pre-slit widths or will slit to order, so you don't have to cut strips out of a wider roll.
Nakamoto Forestry also sells the same perf J-channel that Menzies does. Would not be surprised if Nakamoto gets it from Menzies, given the proximity of Portland to BC.
Chris,
Our local lumberyard sources their perforated stock from Menzies.
I was suggesting Nakamoto as a US source, not knowing if Menzies is distributed outside of Canada, etc.
...and then I realized that Trevor is probably in Canada and I'm a step behind in knowing that... :-)
I should get in touch with Menzies and find out if they have any US distributors (hopefully around me), I'd love to use something like that for my next project. Shipping a few 10 foot sticks any distance (or from Canada) is probably not at all cost effective.
Deleted
Chris,
I wonder if it might make sense to get a local metal shop to bend them out of perforated soffit material?