Fastening Asphalt Shingles to Roof Battens
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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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.
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?
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.
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!
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.
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.
Thanks to you both for your input!