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Fastening Asphalt Shingles to Roof Battens

DFWGreenBuild | Posted in General Questions on

I have a roof assembly that consists of a conditioned attic with a VDP at the ridge. My decking is 19/32 plywood with a Mento 3000 wrb and Rockwool comfortboard 80 on top. I am then installing battens and counter battens. I have seen this assembly on numerous articles and diagrams for tile and metal roofs but never shingles. I contacted the shingle manufacturer and they were not much help. I would be affixing the nail strip of the shingles to a wood batten, so I don’t see how this could be a problem but the lack of information and examples out there is worrisome. Is there some issue I don’t forsee? Or is it just that generally with this type of roof assembly people don’t ‘cheap out’ with shingles and it’s used primarily with more expensive roofing?

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Replies

  1. kbentley57 | | #1

    I think I might be better to include a sketch here. From what I'm visualizing, the shingles would curl in nearly hours. They need full, flat support underneath, for the most part. I wouldn't want anything larger than 1/4" between sheathing gaps.

    1. DFWGreenBuild | | #3

      It'd be similar to this but with shingles instead of tile

      Edit: I could easily do the battens very close like the second picture. Do you think that would alleviate the concern of cupping and walking on the roof?

      1. kbentley57 | | #4

        DFW,

        I'm sorry to say, that it wont work, at least for asphalt shingles. Metal shingles, on the other hand would work here, thought I know that's not what you asked. You could on the other hand just install a layer of osb/plywood on the vertical battens, and install your shingles there. That's probably much less work as it is, than installing the counter-battens.

        1. DFWGreenBuild | | #5

          I'll check out metal shingles, thanks for the suggestion.

          Do you mind if I ask 'why' the asphalt won't work? You seem quite certain but as a newbie myself, I'd like to understand why it wouldn't work? I appreciate your time and answering my question (s). Thanks!

          1. kbentley57 | | #6

            The reason is that shingles are very soft, especially so in the full sun. They're really nothing more than a fibrous material holding asphalt and topped with gravel. They'll simply sag through any unsupported span once they reach temperature.

            That happens very quickly - A shingle can go from ambient temperature to 160-170 degrees F in full sun in a matter of minutes.

  2. Expert Member
    MALCOLM TAYLOR | | #2

    No. It would void the warranty, but more importantly you couldn't even get them installed without damaging them, never-mind walk the roof afterwards. Unlike the other types of roofing which can be put on battens or skip-sheathing, shingles have no inherent structural strength and rely instead on a flat, sturdy substrate for support.

    From a typical manufacturer's instructions:
    ● Plywood or OSB... 3/8” minimum thickness, exterior grade as recommended by
    APA – The Engineered Wood Association
    ● Wood planking... Nominal 1” thick (min.) x 6” wide (max.) wood planking, with a
    maximum 1/8” spacing at the ends and sides.

    1. DFWGreenBuild | | #7

      Thanks to you both for your input!

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