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Community and Q&A

Insulating Exterior Sheathing Over Gable End

drewintoledo | Posted in Green Building Techniques on

I’m covering the exterior sheathing with 3″ Rockwool held in place with 1×4 furring. The gable end is not insulated so I opted to omit the rockwool and simply use (2) 2×4’s stacked flat with a 1×4 on top.  I’m hopeful to gain feedback before I begin, good or bad? Thank you

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  1. Expert Member


    That will work fine. Rather than stack the 2"x4"s I'd consider running the first layer @48"oc to save lumber.

    If the gables have different cladding, or there is a trim board at the bottom, you may want to just add a cap flashing instead, and omit padding out the gables.

  2. drewintoledo | | #2

    48" OC is interesting. I've never heard of that before. I do plan to transition to shake style siding and I thought about doing the cap flashing but I have a couple of rooflines on either side of the gable and I'm unsure how to integrate them together.. I guess step flashing would do it. I am probably going to have it over to a siding installer to figure out. Boy, it'd be real nice to avoid adding furring up there if it would look OK. Thanks for your reply Malcom, you are always so very helpful.

    1. Expert Member
      MALCOLM TAYLOR | | #3

      Good luck with your build!

    2. Expert Member


      If you plan on installing the fiber cement version of the shake siding, with the slits running up, it's a jigsaw puzzle trying to get it right where the gable meets the roof line. I used nichiha straight shake over 2x4 furring strips on a 7:12 pitch, and it nearly drove me crazy, even at 16" OC. I'm not quite sure how to describe the frustration, but I got it worked out, after a lot of shifting first cuts around, etc. If you're not careful, you'll saw off a section through one of the slits, and have no furring strip to nail the short section to. Id have rather used the LP smartside version, which would have made it 100% simpler.

      Those products are really made to go flat on the wall. Your siding guy will have almost certainly never have installed it over furring strips, and will likely run into the same trouble if he tries to just wing it.

      It depends on the look you want, but I would think a siding recessed 3" behind another might look a little off. There's a lot of ways to fur it out, it might actually be easier to cut strips of XPS or EPS into 3.5" wide, and sandwich behind the 1x4. It wouldn't take that much, and it's certainly easier to lift / install than stacked 2x4's. You could probably do it on the ground, using one of the Loctite PL adhesives. It's light, strong, cheaper, it just takes more labor.

      1. Expert Member
        MALCOLM TAYLOR | | #5


        The problems you had may be specific to the type of cement-based shingles you used. This is one of several gable ends of a house I built a few years ago using Hardi shingles over rain-screen strapping @16" oc. It went fine.

        1. Expert Member
          KYLE WINSTON BENTLEY | | #6

          You're probably right, though it made me want to swear them off for a while!

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