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Soffit vent screen size?

user-2642926 | Posted in General Questions on

I am at the tail end of a major remodel / expansion, and my soffit vents are a detail yet to be completed. As built, the framers simply drilled 1.3″ holes in the vertical board between the rafters sufficient to meet Accuvent’s recommendation for vent area.

The house is in Southern California, so we not only have bees and flying termites, but a variety of other critters that could cause trouble.

The smaller I go on the mesh size the better it is at screening out small insects, but it comes with a cost: reduced airflow.

Can anyone comment on a good screen size for this instance?

Thank you for any suggestions.

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  1. Expert Member

    What ever size you decide on don't rely on insect screening. Either use perorated soffit stock, or back up the screens with 1/4' galvanized mesh. Rodents and birds make short work of screened vents.

  2. GBA Editor
    Martin Holladay | | #2

    It sounds like these are holes in the fascia. Just drilling holes and walking away isn't very professional. (And I've bought a lot of bits in my day, and I've never heard of a 1.3 inch bit. Maybe 1 1/4 inch?)

    Lots of manufacturers make soffit vents for round holes -- but 2 inches in diameter is more common than 1.3 inch in diameter. Here is a typical product:

    The trouble with inserting this type of round vent in a fascia instead of a soffit is that you have to worry about water dribbling down the fascia and catching on the lip of these vents, leading to rot. The wider your dripedge, the better.

  3. Expert Member

    If you decide to use the plastic vents Martin linked to, fasten them with screws. Although they are designed to friction fit, over time they tend to fall out.

  4. user-2642926 | | #4

    Thank you for the answers so far. I will check out those plastic vents to get a sense of their mesh.

    Martin, yes and sorry. That was the minimum hole size required to achieve the venting. I believe they drilled 1.5" holes in the 2x6 boards.

    I don't expect any problems with water, as these are tucked well up and back of any exposure to rain, under a 2' eave. The construction of this allows me to install any screening I'd like in front of the holes on that board and install *another* 2x6 in front of that.

    All this discussion has me thinking about alternate options. I just got off the phone with the manufacturer of Vulcan Firesafe soffit vents. They're not... inexpensive, but they prevent embers from entering the house in addition to bugs) If I get their continuous soffit vent, I can use a bandsaw to but it to length and trim it out accordingly.

    I'm seriously considering that option.

  5. Expert Member

    What I usually do when the venting is in the blocking between rafters is cut a finished block 1 1/2" shorter, and install a U-shaped piece of perforated flashing in between the block and the roof sheathing.
    Fire resistant vents may be a very good idea depending on where you are building though.

  6. user-4524083 | | #6

    Mike - Over the years, I've come to rely upon stainless steel, heavy gauge, insect screen. Same hole size as regular insect screen, but thicker gauge and a "forever" product. One company is . The company also sells all kinds of perforated sheet metal products. I also use this heavy screen to make gable vents squirrel proof. It makes a great detail for exposed rafters: you staple it to the top of the sheathing, between the rafters, then side up to where you want to stop, say 2" from the top, and cover that edge with a small piece of trim board, cut to also fit between the rafters. On the top, at the roof sheathing interface, I would use 3/4 inch plywood for the sheathing (this was for a slate roof, so i wanted the extra thickness) but v-match boards for the exposed part on the overhang. This takes planning, but I would make sure that one of the V's lined up with the sidewall/ siding. So the top did not need to be stapled, just slipped into the V-groove, making an almost invisible vent. The screen was stiff enough of a gauge that I could not push it out once it was in place. I don't know if this solution is appropriate for your situation, or not, but it sounds like you could remove the 2X6 the framers put in, and do a full length vent, either using Malcolm's idea ( which I didn't quite follow. Where does the U side go?) or some type of heavy screening.

  7. user-2642926 | | #7

    Thank you Kevin! That looks like an ideal product. I'll call McNichols and see which mesh they recommend for my application.

    I'm pretty sure Malcolm's suggestion would have the U facing to the rear, fastened between the top of the block and the bottom of the roof sheathing. It's also a creative way of doing this, but the blocks are already installed, painted, etc so I'm looking for a slightly different solution.

    Yours seems ideal. I have some ideas on how to make it look good and I think it should be pretty simple... though time consuming since I have a LOT of these screens to install.

    Thanks again everyone.

  8. Expert Member

    The U shaped flashing, made from the same perforated stock we use for the bottom of rain screens, has one leg longer than the other (J shaped might better describe it). I pre-make the blocks, nailing the longer leg of the flashing to the top of the wood so that they are the same height as the rafters. They get nailed into place from the sides and friction fit against the roof decking above. I do this as I install the rafters so there is no rough blocking behind.
    In Mikes situation, where he already has blocking and holes drilled, your solution sounds like a much better idea.

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