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Community and Q&A

Installing Hardie panel vertical siding over 2.5″ EPS

seanprokopec | Posted in Green Building Techniques on

I have come across the opportunity to purchase 2.5″ Type 1 EPS insulation for very cheap per sq ft and would like to apply it along with new Hardie Panel vertical siding.

I’ve researched about attaching horizontal furring over the insulation but have come to the conclusion that there are no fasteners available that recommended installing furring over Type 1 EPS. The only other solution I see is attaching horizontal furring to the studs in behind the osb sheathing and fitting foam tight in between.

Does anyone know of any other solutions to this scenario? And if not, how would you recommend proper air sealing of this arrangement, I was planning on wrapping over insulation with housewrap.


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  1. GBA Editor
    Martin Holladay | | #1

    You can certainly install furring strips over EPS. For information on this issue, see Fastening Furring Strips to a Foam-Sheathed Wall.

    Installers of James Hardie products often ask, "Do I need 2x4 furring strips, or is it acceptable to use 1x4 furring strips?" The answer from James Hardie is, "It depends."

    Fortunately, James Hardie has released a technical bulletin that explains how you can answer this question. Here is the link:
    James Hardie Technical Bulletin #19: Applying James Hardie Siding over Continuous Insulation and Non-Nailable Substrates.

  2. seanprokopec | | #2

    I read through the article "Fastening Furring Strips to a Foam-Sheathed Wall" and Fastenmaster's recommendations apply to Type 2 EPS or similar density material. I read through there technical document "“Attaching Exterior Wall Covering Assemblies with Foam Sheathing to Wood Wall Framing,” as well where they stated this. I'm assuming there is issue with the lower density EPS compressing under the load apply from the fasteners and furring strips.

    Have you or anyone else ran into an issue furring over Type 1 EPS?


  3. seanprokopec | | #3

    Type 2 EPS has a much higher price tag.

  4. Expert Member

    As long as you follow the recommended spacing and size of fasteners, loading won't be a problem. What can be is getting your furring flat if the foam compresses, but type 1 EPS compresses a lot less that mineral wool board, and builders manage to get it co-planar with a bit of care.

  5. seanprokopec | | #5

    In your experience, is there a fastener that performs better than the rest, price a consideration as well?



  6. Expert Member

    I favour GRK fasteners, but there are several comparable ones made by other manufacturers.

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