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How much space between individual 1×8 boards for vented soffit

derekr | Posted in General Questions on

I only need 10 more feet of soffit and having trouble getting what I want

im thinking about just using 1×8 cypress in the last small section, how much space would I need between each board to have the correct amount of air flow?

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  1. Expert Member
    Akos | | #1

    You don't want a gap as pest will get in there. What you want is a continuous perf vent strip like this:

    Box stores sell a version that is a simple hat shape that will also work.

    If you go with black ones, I find it is best to put this right by the top of the wall at the first soffit board. This way it pretty much disappears into the shadow and it is not noticeable at all.

    Bit more work, you can also router a slot in the soffit boards and staple hardware cloth above it. The area of the slot should match the required ventilation area for your roof.

    1. derekr | | #2

      This is just a very small roof that sticks out from the larger roof it’s like 5x7 the venting is 5 feet on each side, I could cut the 1x8s in half so I could have more slots but narrower

  2. Expert Member


    If you are spacing the boards and covering the spaces between them with insect screen, you first need to calculate how much total venting the roof requires, and then see what that amounts to in terms of the voids between the boards. The total area will be either 1:150, or 1:300.

    I'm not keen on relying on insect screen, especially when it is attached to the top of the soffit material, as it is easily damaged, and difficult to access to re-install.

    1. derekr | | #4

      This is a small dormer that connects to the larger roof, 5 feet of venting on each side

      Like standard vinyl soffit has 5 inches of airflow i think? I forget how they word it, how much space would need to be between the board just to achieve the same amount of airflow that vinyl soffits provide

      Edit: Ok I figured the dormer has 35 sqft of attic space and the larger part it’s connected to has 170 sqft

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