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Community and Q&A

Working With Zip System R-Sheathing

drewfridley7 | Posted in General Questions on

I am building an 8×24′ house on a trailer. I have framed the walls in eight sections. (24′ into three sections for each side and the two end walls. One section before the wheel well, one on top, and one after. Section sizes are about 12, 6, and 4 feet long.) I would like to attach one-inch ZIP R sheathing for added insulation and a continuous thermal break. I have this chart on installation: https://hillsidelumber.net/wp-content/uploads/2018/06/zip-r-boise.pdf

I have a couple questions:

I would like to attach at least a row or two of sheathing before standing the walls to keep the walls square. Since I am building in sections, it seems the best thing to do is attach a piece of sheathing to the four front and back walls on the long sides. Does this make since? Knowing I will cut a piece of sheathing to fit in the middle of those two to cover the middle section plus a little more?

On the chart, the minimum penetration into the framing is 1.5″. Is there a method to fastening ZIP R so as to not damage the insulation? Does tape go over the fasteners? I do not understand how it will be a continuous thermal break if I am putting hundreds of nails through it to attach it to the framing.

Any other wisdom on installing ZIP R is welcomed! If any other info is needed, please ask! Thanks!

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Replies

  1. GBA Editor
    Kiley Jacques | | #1

    I'll respond to your call for "any other wisdom on installing ZIP R" by recommending this article: Working With ZIP System R-Sheathing, which includes advice from Jake Bruton.

    1. drewfridley7 | | #2

      Thanks Kiley! Reading that article a few months ago inspired me to use ZIP R. Now I am in search for answers to these more in-depth questions. Thanks again!

  2. Kyle Bentley | | #3

    Drew,

    "I would like to attach at least a row or two of sheathing before standing the walls to keep the walls square. Since I am building in sections, it seems the best thing to do is attach a piece of sheathing to the four front and back walls on the long sides. Does this make since? Knowing I will cut a piece of sheathing to fit in the middle of those two to cover the middle section plus a little more?"

    You can do it this way if you want, but what might be easier is to screw in a temporary brace across the diagonal on the opposite side of the wall. use a 2x4 or any other scrap lumber and you'll save a lot of weight, while keeping it perfectly square while you nail up the sheathing.

    "On the chart, the minimum penetration into the framing is 1.5″. Is there a method to fastening ZIP R so as to not damage the insulation? "

    Singe you're going to have some amount of waste, cut off a sacrifical section to test with. Calibrate the penetration depth by adjusting the air pressure regulator and shooting a few nails into the sheathing / 2x4 until the nail heads are *just* overdriven by maybe 1/32". You want the heads flush, but you don't get the rebound that exists in a vertical stud by testing it on the ground. You don't want to have to hammer many nail heads flush if you can help it. Use 2 3/8" hot dipped galvanized ring shank nails and you'll have sufficient penetration into the studs. They're a standard size, and slightly longer nails are somewhat hard to find at the big box stores.

    If you fasten by the guidelines, the tape will cover the rows of nails on the sheathing seams. You'll want to drive them in at a slight angle towards the center of the stud, don't be alarmed if theres a slight difference in plane between the sheathing and the head of the nail. It's fine, and it'll be covered by the tape anyways. 4" OC around the perimeter, and don't over-nail the field, 12" OC is enough, and stronger than driving it home 4" there too.

    " I do not understand how it will be a continuous thermal break if I am putting hundreds of nails through it to attach it to the framing."

    You're correct. It's not a thermal break in that regard. However, I think you should compare it to normal zip, not exterior continuous insulation. In this regard, you've got insulation everywhere between the studs and sheathing, whereas before the sheathing and studs were in direct contact. There's a lot of area there that now has insulation between the surfaces that didn't exist before. Think of it as an easy way of extending the stud depth, with a small added bonus of a thermal break between the studs and sheathing, albeit with a a lot of short circuits that would have otherwise always existed.

    That's relating to the advice we'd mentioned in the previous thread - Zip R is not continuous insulation (CI). It's better than non zip R in thicknesses where it's still easy to nail, but inferior to CI in terms of R value, and shear capacity at the same thickness of CI and sheathing.

  3. Walter Ahlgrim | | #4

    I like the Idea of Zip sheeting but fail to see the appeal of the +R product.

    I think post #2 by Kyle Bentley in this thread describes my feeling about Zip+R better than I can put into words.

    https://www.greenbuildingadvisor.com/question/how-to-install-siding-to-zip-r-sheathing

    Seems to me if you are ever going to move this trailer you can’t afford to lose the shear strength that will happen you put the soft foam between the sheeting and the framing. I think 5 miles down a hilly gravel road +R wall is likely to be close to collapse.

    Walta

    1. Kyle Bentley | | #5

      Walta

      I doubt it's really in any danger of collapse, in fact it might actually help give it just enough flexibility to move around as it's being transported and not cause any permanent deformation of the nail/sheathing interface. Though now that you mention it, moving it down a highway might subject it to quite a bit of wind force. There's probably somewhere around 0.25 PSI worth of head wind force at those speeds, something that I think even zip r should handle ok, given the frontal area and aspect ratio of the house.

      You're right though, the thread I was referencing was that one, also by the OP.

      1. Expert Member
        Malcolm Taylor | | #6

        Kyle,

        I agree with Walta, that your reservations about Zip-R hit the spot for me.

  4. Walter Ahlgrim | | #7

    If I were to build a trailer, I would have plywood glued and screwed directly to the framing.

    On a gravel road you will get a shear event every few feet 2000 per mile. How many times can you tug on a nail in chip board before the waswood disintegrates around the nail?

    Travel trailer factories don’t use Zip+r and 2x4 because it to thick, heavy, fragile and expensive.

    Walta

  5. Expert Member
    Michael Maines | | #8

    Is this a house that will only move on rare occasions, or is it more like an RV? For a relatively stationary house I think Zip-R would work fine; their testing was pretty rigorous. You could add diagonal metal straps if you're concerned. But if it's something you plan to move regularly, I would refer to the IRC for guidance, using seismically active and high-wind criteria. That will preclude using Zip-R for shear resistance.

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