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Trim on top of siding or butted against?

Kevin McGuire | Posted in General Questions on

I’d say this is an easy answer if we were talking about lap siding. However I’m going for the classic board and batten look, using 4×8 sheets of hardiepanel rather than 10” boards. No foam in this application, 3/4” furring/rainscreen. Using either primed whitewood or cedar for trim. Haven t decided on that…

Essentially the the question is this: trim, or panels first?  I know what’s easier, but not sure if it matters.

Panels first would mean my cuts around windows and doors wouldn’t need to be as precise. I also wouldn’t need to metal flash the head trim either, probably just the window itself. I would then just bevel the top of my header trim slightly and bevel the battens accordingly and caulk that joint.

I don’t see much of a problem with this, or am I missing something? since my panels are smooth, as opposed to textured, or lap siding, again I can’t think of anything wrong with this – sort of like hanging drywall.

(opinions needed – window/door/corner trim sitting proud of battens, or flush?  Battens -1.5” wide casings/corners – 3.5”  craftsman style windows. They will be same color – white, just 1 sheen difference between trim, and battens/body – considering this in case trim and battens butt up against each other vertically)

thanks again

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Replies

  1. Trevor Lambert | | #1

    Trim over the panels. Hardie has an installation manual that you can find online that spells out all the options. I have the exact same set-up as you, smooth panels with board and batten.

    The opinion questions are really just personal preference. I went with flush. I'm guessing you're not using Hardie for the trim and battens? Otherwise, your battens would be 2.5" rather than 1.5". I think 2.5" is a more appropriate size, both in terms of covering the seams and nails as well as style.

    1. Kevin McGuire | | #2

      I hear what you’re saying about the manuals online, I just tend to trust the GBA community a bit more than most other resources - even manufacturers.

      The reason I didn’t want to go with hardie battens was because of the width. I just think 2.5” is too wide, even at panel joints, 1.5”-2” is plenty to cover, I think, screws, panel gap at 1/8” max if you opt for that, considering screws are about 1/2” from edge of panel. - that’s about 1-1/8” to cover, so 1.5-2 seems plenty. But you’ve done this, I haven’t.

      Lastly, most B and B I see have 1.5-2” battens. I simply almost never see 1x3. Perhaps if you’re spacing them 16oc instead of 10”oc, the 2.5 would look ok.

      Question: did you caulk panel joints, and batten over panel joints? I guess you wouldn’t need to with hardie bats?

      1. Trevor Lambert | | #3

        If you're installing the panels yourself, you'll likely be fine. I had no problem keeping the nails to pretty close to 0.5" from the edge. Don't forget to include the radius of the screw or nail head when considering maximum space from the edge; two screws about 1-1/8" on centre require at least 1-3/8" to cover. However, I sub contracted out a lot of the panels, especially on the second story and gables. Despite having spelled out the requirements and showing an example of my expectations, the subs were rather inconsistent in their nailing. Even on the nail lines mid panel, where all they had to do was hit the centre, I am having to "best fit" the line in order to cover all the nails instead of putting it dead centre. And I was paying them by the hour, so they had no reason to rush. I can only imagine it would be worse if I was paying a flat rate.

        My batten spacing is 24", so that definitely makes a difference. At 10" spacing, it would look very different.

        There's four approved methods of handling the panel joints.
        1) Leave a 1/8" gap, and caulk
        2) Join with an H profile piece of either plastic or aluminum
        3) Cover with battens
        4) Lightly abut the panels and leave uncovered

        So you can see that even if you don't cover the joints, there's no requirement for caulking. If you cover them with battens, there's even less incentive to caulk. Which is a good thing, because caulk is just going to fail at some point anyway, and you don't want it to fail in hidden areas. I have a rain screen, so I really don't care if a small amount of water gets behind the panels. I don't know what stage in the build you're at, but if you can incorporate a rain screen that is an extra level of insurance that is worth the effort, IMO.

  2. User avatar GBA Editor
    Peter Yost | | #4

    hi Kevin -

    When I was a carpenter now quite a long time ago, I thought you caulked everything tight as well as butted everything tight to "keep the water out." Essentially a face-sealed cladding system. I did not understand how water or wood building materials worked.

    Sealant only keeps water out for as long as it stays bonded to the substrate. After that bond breaks, now the sealant let water in and retards vapor drying. Best way to protect wood is to let it see as much air as possible: on its back side and at joints. Gap everything. Any sort of wood building material will thank you.

    Peter

  3. Scott Wilson | | #5

    So what do you do for horizontal trim pieces, such as the trim over the window? I'm guessing that a thicker piece of exterior window casing is nailed to the sheathing, then metal flashing over the top piece, then the Hardiepanel over the flashing (leaving a small gap between the bottom edge of the panel and the flashing) then the battens? Any vertical battens above the top piece of horizontal window casing would then be installed (how much of a gap between pieces)?

    1. Malcolm Taylor | | #6

      Scott,

      If the trim is being applied over the Hardi-panels:

      - The head-flashing is installed in a bed of caulking onto the top of the window frame.
      - The WRB is lapped over the head-flashing, or the flashing is taped.
      - The rain-screen battens are run down to the top of the window flange.
      - The cement-board panels are fastened to the battens. At the head the panel is kept up about 3/8" .
      - The horizontal window trim at the head is kept up 1/8". This means you need to cut kerfs in the trim to set it down over the end-dams in the head-flashing.

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