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Insect Screen for Metal Siding

I'm looking for a detail for integrating an insect screen with vertical corrugated metal siding that is meant to function as rainscreen.

Are the typical metal J-trims and flashings enough to keep bugs out of the corrugated flutes or is there a better way?

Asked by Daryl Ross
Posted Jul 12, 2014 10:45 AM ET


7 Answers

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We use a perforated pre-finished L flashing at the bottom of our rain screens when we use corrugated metal siding. While not as tight as the U shape used with other siding, It fits pretty well. I have never seen carpenter ants manage to bypass it but I'll bet that if I removed a section of siding after a few years there would be small spider webs and the odd bug - the same as you find in any cavity construction like brick. I don't know of any way to completely seal the intersection off without compromising the rain screen function of the wall.

Answered by Malcolm Taylor
Posted Jul 12, 2014 11:38 AM ET


You could order a custom J flashing with the bottom of the J perforated and wide enough to span from the back of your strapping to the outside of the ribs.
If the metal sheets sit square against the bottom of the J, it should be good enough.

J trim.jpg
Answered by Lucas Durand - 7A
Posted Jul 12, 2014 2:41 PM ET
Edited Jul 12, 2014 2:43 PM ET.


Corrugated siding installed vertically works as a rain screen without furring. It meets our code here in BC which allows any material that only contacts the sheathing behind 8% or less and maintains a drainage plane.
The problem with using a profile with a lip, like a J trim, is that where the siding waves inward the J trim traps debris.
If you really want to complicate things, try the same detail where there is another siding, like say fibre cement , on furring strips below the corrugated galvalum. That's a whole other headache.
Bugs, water, moulds, rodents - and they say nature is our friend...

Answered by Malcolm Taylor
Posted Jul 12, 2014 6:02 PM ET


Hmmm, interesting.
I had never heard of that code reference before and what you say about the lip trapping debris makes sense.

Funny, but I did the reverse of your more complicated detail on my house.
On the walk-out portion of the basement, I wanted something other than wood siding so close to grade and I had enough material left from doing the roof that I cut the left-overs down and clad the bottom 32" of those walls in galvanized steel.
Being as frugal as I am I just used what I had on hand to keep bugs out of the rainscreen gap (ie: aluminum insect screen and foam "closure strips" to close the rib ends) and remember thinking that I should have just ordered a perforated J trim for ease of installation...
But maybe I should have been cursing myself for not just ordering up some L flashing...

Anyway, as you say, I think a few little spiders aren't a big deal - you just don't want a wasp nest or flies getting back there.

Ever try using a clear thermoplastic sealant at the seam between the steel panel and the perforated trim?

Answered by Lucas Durand - 7A
Posted Jul 12, 2014 9:30 PM ET
Edited Jul 12, 2014 9:32 PM ET.


"Ever try using a clear thermoplastic sealant at the seam between the steel panel and the perforated trim?"
No, I don't think it's worth it. As you say what you are trying to keep out are colonies that will nest and block the cavity or eat the wall. The odd small bug shouldn't be a worry.
Have you had any time to work on your place this summer? I refer a lot of people to your site. It's a very nice build.

Answered by Malcolm Taylor
Posted Jul 12, 2014 11:42 PM ET


Malcolm, thanks.
I have been spending a lot of time on the house lately.
Stairs are in, partitions are all in, working on ducts for the HRV and plumbing now, and the electrical contractor starts this week - I'm hoping to get occupancy before this winter sets in but we'll see...
There's lots to add to my blog but trying to find time for that has been tough lately.

Answered by Lucas Durand - 7A
Posted Jul 13, 2014 7:33 PM ET


I look forward to it when you do get the time. Just happy to hear things are going well.

Answered by Malcolm Taylor
Posted Jul 13, 2014 11:39 PM ET

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