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Difficult building inspector

user-4405197 | Posted in Building Code Questions on

Needless to say our Building Inspector is real charmer, and on top of that is very unfamiliar with energy smart building techniques. We are putting up 3″ of Roxul comfortboard followed by 1×4 furring strips and Hardiplank fiber cement siding. The inspector wants proof from James Hardie that this method is acceptable and safe. We sent him this document from Roxul where they had Building Science Corp conduct a study on deflection using our exact cladding system.

Has anyone else had a similar issue with their Building Inspector? And can anyone post a link or two that I could forward him that shows this isn’t just some “off the cuff” wacky system? I know there are articles galore on GBA about this building technique, but if you know of any links to technical documents like ESR reports from James Hardie, that sounds like what he’s looking for. He mentioned that James Hardie only allows their siding to be attached to furring strips that are in direct contact with the sheathing. He said he read that in one of their ESR reports.

I know I’m not crazy here, but the Building Inspector sure makes me feel that way. Any help would be appreciated. Thank you.

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  1. Expert Member
  2. user-4405197 | | #2

    Thanks Dana.

  3. Jon_Lawrence | | #3


    I have the same exterior wall assembly as you. I have not filed for permits yet, but I had to provide my structural engineer with sufficient documentation to get him comfortable with this assembly. As part of that, I included the fastener guide from Roxul that I have attached. On page 4 of that guide, there is a reference to an NTA Engineering Evaluation Report that provides guidance on the fastener spacing based on total weight per fastener using the TRUFAST SIP fastener. That report is to big to attach here, but if you search you can find it online.

  4. GBA Editor
    Martin Holladay | | #4

    Your negotiations may be frustrating, but try not to label your building inspector "difficult." Installing siding to furring strips installed over a continuous layer of mineral wool is unusual, and your building inspector is doing his job. Lots of us, including building scientist John Straube (and me) were skeptical about whether this technique would work, until the Building Science Corp. did the lab work to verify that it would work.

    Your building inspector is making sure that when you sell your house to the next owner, the next owner won't have an ugly surprise. Every house needs to have well-attached siding. With patience, you should be able to provide the documents your inspector needs. If necessary, you can hire an engineer to help prepare the necessary documentation.

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