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Community and Q&A

Bug screen for rainscreen strapping…how wide to cut?

unclejemima | Posted in General Questions on

I’m a rookie with this. First time building a rainscreen. I’ve got my WBB on the house and would like to apply my 3/8 strapping to create and airgap.

I picked up a few hundred feet of 4′ bug screen and I will first apply a layer top and bottom, then my strapping and then staple the bug screen on-top of the strapping making the air gap, hopefully, bug free.

So, question. How much bug screen do I need to apply? I was thinking 6″ strip, staple to sheathing/WRB 3″ up, then wrap it over-top giving me 3″ wrap. Is this enough? Basically, its just the bottom that will be covered that’s important, but curious how far guys wrap it up the sides?

I was going to do ridge vent but its $$$!!!

Thanks in advance

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  1. unclejemima | | #1

    Oh, and I suppose I should probably put my aluminum window drip edge on before the bug wrap.

    So steps...WRB, window drip edge top and bottom, bug screen, strapping. Sound right?


  2. Expert Member

    Mark, hardly anyone uses bug screen at the base now - it was too vulnerable to damage. Use either a U shaped or L flashing made out of perforated metal. All the lumberyards here stock them, but if they don't where you are you can get them made up, or if you have a break make your own.

  3. GBA Editor
    Martin Holladay | | #3

    You may find some useful information in the following article: All About Rainscreens.

    Malcolm gave you good advice.

    If you still want to use insect screen, I think that 6 or 7 inch strips would be adequate. I'm attaching a few images showing you how other people have done it.


  4. Expert Member
    ARMANDO COBO | | #4

    I recommend Cor-a-Vent siding strips and bug strip at the top and bottom. It comes to about 31¢/lf vs. 29¢/lf for 1x2 primed pine strip here in TX, and it is less money than 1x4s; however is a lot more reliable and durable than wood. The top and bottom strips (Cor-a-Vent SV-3) has an insect screen built in. Its also 7/16"x3"x4', so it helps with shallow window profiles.

  5. unclejemima | | #5

    Thanks guys.

    Buying cor-a-vent in Canada is like buying moon rocks at the 711. Its basically no-existent. I wish it were sold up here.

    Next time I will pre-order it..that and the CAD is really weak right now making it even more expensive.

    As for the vented perforated flashing...can't find it up here either. I'm probably the first guy in town to do a rain screen...and I'm not even kidding!

    If you guys are finding this at a hardware store...are you talking home depot or such? I'd be curious what the SKU is and I can run it on the system here if it pulls anything up.

  6. Expert Member

    Mark, All the lumberyards sell it here in coastal BC because our code mandates rain screen. Before they began stocking it we used to get our gutter and soffit subs to make it up out of their perforated stock.

    If you look at most of the old bug screen installations they have damage. Either from small rodents or letting grass grow up into the cavity and yanking it out.

  7. unclejemima | | #7

    Thanks Malcom. Can you amuse me on what lumber yards carry this? Any chain stores?

    I was just at the gutter and soffit shop today to get some drip cap bent. I did not know they even had any perforated stock? What would they normally use it for? I'm in Northern Alberta, so getting freight from coastal bc is not to big a deal, but would like to get it locally.

    I'll check with the soffit guys on Monday.

  8. Expert Member

    I'm on Vancouver Island. Slegg Lumber in Langford and Home Lumber in Victoria both have common sizes in stock, and Slegg will make any custom profile you want. Before that I used to get Irwin Industries to make it out of their perforated soffit material.
    The link in my previous post was to Menzies Metals, which has an outlet in Nanaimo, and may have stores closer to you.

  9. unclejemima | | #9

    Hi Malcom,

    I got laughed off the phone again when trying to even find periforated stock...but finally found a shop that would make some for me. galvanized metal 24 or so gauge with 1/8" holes 3/16" apart.
    Total cost would be about $10 for 10ft if I had 100 made. Does that sound about par to the lumber yard units?

  10. Expert Member
    MALCOLM TAYLOR | | #10

    Mark, I'll call my sales guy at Sleggs tomorrow and get a price. You can also get a quote from Menzies from the link I posted if you'd like.

  11. DIYJester | | #11


    Now I just have to find a product similar for me in the states. I've thought about just putting some vented soffit in a brake and bending it.

  12. Irishjake | | #12


    I would caution you against using the screen material alone. Vermin, mice, etc., chew through it easily, and once they are there, so is everything else. If you can't go with Cor-A-Vent or the Menzie screen add 1/4" square galv wire mesh to the underside of the bugscreen to prevent the vermin from chewing through it. It comes in rolls and is available almost everywhere.

  13. dburgoyne | | #13

    I was able to special order Cor-A-Vent through Home Depot a few days ago. It didn't show up on their website, but they were able to find a supplier and order it through them. You can also call Cor-A-Vent and ask them where you can find it near you. The cost I found was higher than what others quoted though, ~$1.50 per lineal foot.

  14. Expert Member
    MALCOLM TAYLOR | | #14

    Mark, Slegg's U flashing for 1/2" strapping is $6.09 for a ten foot length. It's in stock, so no minimum order.

  15. DIYJester | | #15

    I ordered some Cor-A-Vent from ABC supply. After I ordered it I thought of a key question:

    I am insulating from the soffits all the way down ~28" below grade (slab on grade, hydronic heat), do I need flashing at the bottom of the above grade insulation assembly? It would rest right on top of 4 more inches of XPS.

    Also is tongue and groove XPS worth the extra cost if I'm already taping and caulking seams?

  16. Expert Member
    MALCOLM TAYLOR | | #16

    Michael. Yes, you need two pieces. The rain screen strapping stops 8" above finished grade. The vented flashing (or cor-A-vent) seals the bottom against pests while allowing air movement and any water that enters the cavity to exit. The XPS which continues below grade needs mechanical protection. This can be various things - cement board, flashing, parging. If you use something other than flashing, you will need an L flashing 1" below the cor-A-vent to cap whatever material you use.
    Complicating all this is that your WRB is behind your foam, meaning that there is no way to lap your flashing layers at the base of the wall or at windows and doors.

  17. DIYJester | | #17

    I planned on doing outies so I'll be putting the WRB on the outside of the foam.

    I will install some flashing at the interface of where the siding meets the lower section of foam.

  18. DIYJester | | #18

    Well today all my plans went to hell, I found subterranean termites within a foot of my home. I've already got bait set out for a while and will have to spray. It looks like XPS is not an option below grade so I'm going to price putting Roxul Comfort board on the exterior side now.

  19. Expert Member
    MALCOLM TAYLOR | | #19

    Probably small consolation, but great you found out now. I've had too many bad experiences with foam and carpenter ants to use it anywhere but under slabs. There are borate treated foam boards but I've no idea how effective they are against termites or how their treatment fares over time.

  20. Quentin blade | | #20

    yes i like your idea of putting aluminium window edge before the bug wrap. sounds meaningful to me

  21. DIYJester | | #21

    Just in case anyone was interested, I got my Cor vent SV3 today. I'm pretty disappointed in the bug screen. It is nothing more than some thin fiber type mesh. I expected some type of metal screening. I guess I'll still have to add metal screening over top for piece of mind.

  22. hughw | | #22

    Does anyone know if Menzie's sells in the USA? if not, does anyone here sell similar perforated metal channels?

    1. brettske | | #23

      I used some when I built my house in WA. I went online and ordered it. The only drawback is they only ship 5 foot lengths.

    2. Expert Member
      MALCOLM TAYLOR | | #24


      Another alternative is to get a fabricator to bend up the profile from common soffit stock.

  23. Tyler_in_Ontario | | #25

    For any fellow Canadians reading this tread, I was at Home Depot today and picked up anti-rodent trim. Cost was about $5 for 10 feet. The holes are around 1/8"
    Item number 061248649512 or 1001404273

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