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Community and Q&A

Rainscreen

Jason Dennis | Posted in General Questions on

New construction in CZ3 (southeastern NC).

2×6 exterior walls @ 24″ OC with 7/16″ vertical ZIP sheathing. NO exterior foam.

Hardie fiber cement lap siding.

Dense pack cellulose in the walls.

Wrap around porch covering the entire front and one side of the house.

Average about 55″ rainfall per year.

I’m assuming a rainscreen would be a good idea in my situation. Furring strips vs drainage mats/mesh? Is one method considered best?

Also, if using 3/4″ thick furring, would that affect my window and door details the same way using exterior foam would? The siding would be 3/4″ further out from the sheathing, windows, and doors, so I wasn’t sure about the affect on the flashing details. Thoughts and experiences?

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Replies

  1. GBA Editor
    Brian Pontolilo | | #1

    Hi Jason.

    You didn't say what kind of siding you were using, but in most cases, a rainsceen detail is a good idea. Most builders choose furring strips over 3D rainscreen products because it is a more affordable option (some say the mesh products are squishy, but they are not). You can either fur out the windows 3/4 inch to have them in plane with this siding, as shown here, or furr out the window trim and make 3/4 inch extension jambs.

    You may find this helpful: All About Rainscreens

    And this: Installing Windows in Thick Walls

    1. Jason Dennis | | #2

      Brian,

      My apologies for omitting the siding info. I'll be using HardiePlank fiber cement lap siding.

      I was thinking that furring out the window trim seemed like a good option since it allowed the window to be installed in the plane with the sheathing like normal. I found details for that at Hammer and Hand here...

      https://hammerandhand.com/best-practices/manual/4-rain-screens/4-2-top-window/

      and here...

      https://hammerandhand.com/best-practices/manual/4-rain-screens/4-2-top-window/

      Aside from furring out the trim, it appears to be a normal window install unless I'm completely missing something. Your thoughts on the Hammer and Hand details?

  2. Expert Member
    Akos | | #3

    Most of the benefit of rain screen is for providing a capillary break for water. To do this you need very little gap, even 3/8" plywood strips are enough. The details hammer and hand show are good, they work with any type of rain screen.

    Drainable mats work but they tend to cost more than strapping, so its mostly used where strapping is not practical such as cedar shakes.

  3. Jason Dennis | | #4

    Maybe a dumb question, but Is the rainscreen still needed on the two walls with a 7' deep porch, or do I only need a rainscreen where I have standard overhangs?

    1. Jason Dennis | | #5

      Anyone have thoughts on the walls covered by porch? Rainscreen still useful or only needed on walls without porch?

      1. Expert Member
        Akos | | #6

        Rain screen under the porch in is a good idea if you are doing very thick walls. Since this is not the case for you, you can skip it. Sometimes it is easier to have the strapping to keep the siding coplanar everywhere.

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