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Community and Q&A

Should you use furring strips under Hardie siding?

Andrew Homoly | Posted in Green Building Techniques on

I plan to build a home with 1.5″ exterior rigid foam insulation and Hardie lap siding. Should I use furring strips to create “the gap” or just nail the Hardie siding directly through the foam? If furring strips are the answer, what specific material should be used for these strips?

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Replies

  1. Expert Member
    Armando Cobo | | #1

    If you go to the manufacturer installation guides, you'll find that you can install cement boards with or without furring strips. There is plenty of information there on how to install Hardie siding.
    You should see two pdf files, one is for Installation Guides and the other is for Better intallation Guides, where you install furring strips.

  2. Andrew Homoly | | #2

    Armando,
    I agree there are plenty of "acceptable" techniques. I would like to hear opinions on what technique is the best and why. Like so many of these topics, there rarely seems to be a universally accepted "best method". On top of that, the code writers seem to be about a decade behind when the best methods are finally determined. It seems to me we are leading the way with conversations like this!

  3. Willy Crane | | #3

    Creating an drainage plane behind the siding with furring strips is well advised if your region receives 40" of rain per year or more. Make sure your rigid foam seams are taped to prevent water penetration and that the surface under the strips will resist liquid water penetration as well. You can use a building wrap or Extruded Poly Styrene. This allows all the water to drain out the bottom without the chance to sit and cause problems. Also add insect screen material to the top and bottom.
    Along with these measures unsure all edges of the siding are at the least primed. Without a complete seal on the Hardie board vapor can water can enter the material and with freeze thaw cycles the board can be expanded and destroyed.
    Good luck with your project!

  4. Daniel McCauley | | #4

    Seems to me like the one thing that can wreck a Hardie install is residual moisture so I can't see how a furring strip install would be a bad thing, as long as you follow Willy and Hardie's advice, prime and paint everything. We just did a HardiePanel install on furring strips using 16ga hat channel with open joints. It's not recommended in any of their literature, but I think if you keep water off of it and keep the edges sealed you should be ok. Good luck!

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