I'm trying to mount a Tesla Universal Wall Connector outside the garage. I have Hardie Plank siding with 7" reveals. The wire box (aka piece of the charger that gets mounted to the framing) has the following dimensions: 9.8" H x 4.7" W x 2" D.

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The rest of the charger attaches on top of the wirebox, once it's mounted.

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Since the box height (9.8") is bigger than the reveals (7"), I think I'll need a mounting block to make it even and looking nice.

I'm currently debating between two options:

  1. Buy a jumbo mounting block like this one (12" H x 8" W x 1.5" D). Drill a 3/4" hole in the middle to pass the conduit going through the wall and terminate into the Wall Connector's wirebox.

    Pros: easy install, fastens with screws, looks nice, no cutting siding.

    Cons: mounting block is an overpriced piece of plastic ($25), drilling a 3/4" hole might crack the vinyl (will it?)

  2. Cut a part of two siding rows, install a piece of vertical Hardie Trim on the now-flat sheathing, paint it, and install the wire box on top of that (per https://diy.stackexchange.com/a/276288/128465)

    Pros: looks more natural and professional, same siding material, possibly slightly cheaper?

    Cons: need to buy an entire trim board (I don't have extras), more work to precisely cut siding and trim to size, need to paint it. Also need to learn how to properly use finish nails without destroying the piece of trim.

I'm leaning towards option #1, but not sure if there are any gotchas there. Also I'm not sure if there's an even easier method that I'm missing.

  • Keep shopping. Big box stores (Home Depot, Lowes), electrical supply houses, hardware stores - all have things designed exactly for this purpose and with either holes already in place or knockouts so you pick the hole position you want. Jan 4 at 5:57
  • @manassehkatz-Moving2Codidact what should I search for exactly?
    – peter
    Jan 4 at 6:03
  • Siding mounting block Jan 4 at 6:12
  • 1
    IDK if this one fits your Hardie Plank, but they do make such things: remodeling.hw.net/products/exteriors/…
    – Huesmann
    Jan 4 at 14:13

1 Answer 1


Use spacers:

cylindrical spacer

The air circulation behind the panel should keep things nice and dry. Aluminum ones should be cheapest due to how easily aluminum can be machined. You want a pretty large outer diameter to get lots of bearing area on your siding.

  • Do you have any pics of what this would look like? I'm skeptical whether this will look good, but happy to be proven wrong.
    – peter
    Jan 4 at 6:04
  • Also are you suggesting spacers directly between the wirebox and the siding? Or siding --> spacers --> mounting block --> wirebox?
    – peter
    Jan 4 at 6:05
  • @peter, spacers without any mounting block. This method looks better than either of your propositions. The spacers are sized just long enough so that the siding doesn't touch the wirebox. The box effectively floats eccentric to the siding, where you would have to push your face against the wall to even see them. If the dimension between the horizontal lines of fasteners is exactly 7", then you would use spacers of the same length. Otherwise each row has its own spacer length to set the wirebox parallel to the wall framing.
    – popham
    Jan 4 at 6:20

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