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Finding an engineer

John P. | Posted in Green Building Techniques on

I would like to put 8″ of rigid foam over a gambrel barn roof, with long fasteners. However, I cannot find a standard guide to the numbers and spacing of screws for the roof. I was going to do screws every 12×12″ (horizontally and vertically), but am concerned this may not be enough.

How do I go about finding an engineer to help calculate the appropriate quantity? This seems like a pretty specialized application, and I would want to use someone with experience. Is there a guide somewhere that lists names and numbers of companies who specialize in this area?

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  1. GBA Editor
    Martin Holladay | | #1

    If you haven't seen it yet, you should read the following article -- an article that provides guidance on screws for your application: How to Install Rigid Foam On Top of Roof Sheathing.

    As the article notes -- and as you apparently know -- if you live in a climate with heavy snowfall, you may need to consult an engineer. In my article, Joe Lstiburek recommends looking for an engineer with experience working in a snowy climate (for example, Aspen, Colorado).

  2. Eric West | | #2

    Most any registered Professional Engineer that does residential work should be able to do the calculation necessary. As Joe Lstiburek and Martin both suggest, finding one that has done it before will help in getting a better solution.

    Atlas Roofing makes nailbase insulation and has some technical guides that I provided to my engineer and architect that helped them determine the fastener pattern even though we weren't using Atlas products.

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