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Hardie Panel install question

kevinjm4 | Posted in General Questions on

I am in zone 4c, and am using hz10 hardiePanel.

There is no note on the James hardie best practice guide about small residential jobs regarding expansion and contraction.. they do however have notes and refer you to another document to find out more about installing the hardiePanel in multi-family or commercial in the context of expansion and contraction.

So my question to the GBA community is this, given your experience: I know hardie doesn’t have a requirement for a small scale job (36’x44’ one story house) beyond what’s already recommended in their install guide (either butter joints or gapped for caulk), but should I at least pay some attention to temperature/climate during the day of install? For example is there anything out there that sounds like this: 80° means no gap in joints, while 40° means 1/8” gap….

ive already laid out my furring strips accounting for 1/16” gap give or take per joint… assuming not every panel will fit perfect, and just generally nervous about “moderate contact” on something with cement in it. So it would be a lot of work to go back and fix this now if gaps were frowned upon in warm weather…. hopefully mine isn’t too big and won’t make much difference.

 all of the information here was taken from pg 114 of the ‘Best Practices – Installation Guide Siding and Trim Products’

one other thing I noticed on pg. 114 is that they have a detail image showing a ‘batten joint’ – and this joint IS gapped, and there isn’t an alternative shown. Does this mean then that hardie panel with battens (which is what I’m doing), requires a gap at panel joints? It is unclear.

So again, with a small residential job, is it smart to pay attention to climate and install accordingly? How so? And second, is my question answered – regardless of climate – given the detail image on pg. 114 showing a batten joint gapped.

thank you.

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  1. Expert Member


    Ideally you would have an 1/8" gap between panels, but I've installed them where the were butted tight without any ill effect and sleep well at night. This one had no gaps:

  2. JC72 | | #2

    CZ3 (Atlanta)

    The Hardie on my home is almost 20 yrs old and the builder caulked the gaps. The caulk has never moved but it looks like crap because of how the caulk has aged. The caulk looks slightly darker than the siding.

  3. GBA Editor
    Brian Pontolilo | | #3


    I have never heard of anyone installing cementitious siding with more or less of a gap based on weather conditions, they way you might with cedar shake siding, for example. Just follow the manufacturer's instructions. And if you are covering the seams with battens and it makes you feel better to have a heavy 1/16 in. gap behind them, I don't think that will be a problem. I haven't looked at the instructions, but my guess is that the gap behind battens is not required, but acceptable, because it will be covered and will make install easier. I could be wrong about that. If you post a link to the instruction, I'll take a look.

  4. this_page_left_blank | | #4

    I don't think you need to sweat this detail. How are you planning on finishing? Hardie has 4 approved methods: 1. Lightly abutted 2. Gapped and caulked 3. Joined by H-channel 4. Covered with battens. We chose number 4, which I think was a good idea. If I was doing all the nailing myself, I would have considered option 1. But you're unlikely to find an installer with enough attention to detail to make that look good. I paid a local builder with a good rep by the hour, so they had no reason to rush. I still had tons of nails nowhere near the proper distance from the edge (Hardie says 3/8", I told them to shoot for 1/2" instead). There are nails so close to the edge that it blew out the edge of the panel, and even a few that can't be covered by the 2.5" wide battens. If you do go with exposed fasteners, make sure you use stainless ones. I'd recommend that in any case, they aren't that much more money.

    The batten joint can be gapped, but it certainly doesn't have to be.

    The one method I'd avoid is the gap and caulk. It won't look good, eventually the caulk will fail, and with a rain screen there is zero reason to seal the joints between panels.

  5. Expert Member
    Peter Yost | | #6

    I am assuming that you are using one or more of the Hardie installation guides, such as this one:

    Having said that: in CZ 4C, I would always install any cladding, but particularly vertical panels, on a ventilated rainscreen system. Just as important as the gap is the hygrothermal stability you will get with that air space behind the cladding.


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