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Community and Q&A

Is sheathing necessary on a chimney chase?

Ben C. | Posted in General Questions on

I have framed a chimney chase of considerable height over my garage.

I was planning on nailing board and batten siding (1×12 Eastern White Pine with 3″ battens) directly to the frame.

The structure is extremely stout, so I don’t need sheathing for racking resistance; can you think of any compelling reason for me to add it?

The flashing will naturally run up behind the siding. Should I refrain from nailing through the flashing?

Side view garage chimney chase photo side view_zpsqc7w6ddj.jpg

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Replies

  1. Ben C. | | #1

    Sketch.

  2. User avatar GBA Editor
    Martin Holladay | | #2

    Ben,
    The main reason to include sheathing and a WRB (integrated with the flashing, of course) is to prevent water entry.

  3. Ben C. | | #3

    The base of the frame is at least 5.5 inches deep on all sides. Do you think enough water could penetrate the siding to cause a problem? Would a little bit of water on the frame present much of a problem? I could always paint the frame with pine tar.

  4. User avatar GBA Editor
    Martin Holladay | | #4

    Ben,
    Almost all sidings leak. Certainly, board and batten siding leaks when there is wind-driven rain. During a rain event, your approach risks having water get behind the flashing. The water could easily show up on your ceiling.

  5. Ben C. | | #5

    You've convinced me to use use 30 lb. felt behind the board and batten. I'll run it down over the top of the flashing. I'll follow up here to let you know how it performs. Thanks again, Martin!

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