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I would like to install lights on the outside of my garage, which has wooden siding with wood about 3/4" thick. Getting power to the location is not a problem (the interior is unfinished and there is power near the spots where I'd like the lights), but I'm unsure how to mount them and an electrical box to the siding. Here's an image of the siding with my desired spot highlighted:

photo of siding next to a garage

The way I see it, there are two issues: adding the box, and making it perpendicular to the ground.

A common solution for this sort of problem seems to be surface-mounted electrical boxes. The most common brand I have found is Arlington, however, they do not appear to offer a shape that would fit where I want to put the light; their siding boxes seem to be built to go at the intersection of two pieces of siding (screenshot from an Arlington catalog):

Arlington surface-mount electric box options

Are there surface-mount electric boxes that might work for me? And if not, what might an alternative approach be? The other ideas I've had are:

  1. Mount a wedge-shaped piece of wood through the siding and into the sheathing, then mount a flat-backed surface-mount electrical box on that. This seems plausible but then the light would have two levels of backing, which seems visually busy.
  2. Mount a wedge-shaped piece of wood through the siding and into the sheathing, then cut a big circular hole in the whole thing and add a round old-work electric box. This would look nicer but would involve more big holes in the house.

I'm curious if there's an easy surface-mount solution that I missed; if one of my ideas resonates as particularly reasonable; or if there's a better approach that I didn't think of!

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    A buddy of mine went ahead and mounted a junction box on a single plank, slanted with the plank so the box is not straight vertical. We have yet to receive a visitation from government agents in sunglasses and big black cars. Jul 12, 2023 at 3:59
  • Yes, if the prospective lamp's base is shorter than the height of a board, the easy button is to simply mount flat on the board. Use an appropriate weather seal, of course (which should be easy since it's flat).
    – Huesmann
    Jul 12, 2023 at 12:56
  • I love the simplicity of that approach, but my lamp's design unfortunately includes a lot of right angles, so I would prefer to have it vertical. Jul 12, 2023 at 21:41
  • ![enter image description here](i.stack.imgur.com/uAHBy.jpg)![enter image description here](i.stack.imgur.com/bVQ30.jpg)I can't comment w/o points, am signed-up jest now. For that other guy's round globe, it's not bad if it's slanted upwards for the light's beam. I'm at the Cottage and am glad I found this page to solve the problem with the light pointing upwards vs. straight out. As usual my hubby asks; what do you think and I go surf the web. Am surprised he didn't think of that, he was gonna chip a Sep 7, 2023 at 14:46

2 Answers 2

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The typical approach here is to alter the siding to provide a vertical surface first, and then mount the box to that. You could do this by cutting a square piece out of the siding (like the red square in your drawing), which would expose the vertical, flat face of the sheathing behind your siding. Then install a new square, consistent-thickness piece of material with a minimum thickness exceeding the thickest part of the removed siding, so it juts out a bit on all sides yet provides an even surface. Then mount a box to that, either to its surface or cut a hole to accept a recessed box.

Example:

enter image description here

The Arlington mounting blocks you reference try to simplify installation of a mounting block by providing shapes that match common siding designs. If you want to attach a mounting block to the surface of your siding rather than cutting into it, one option is to find or buy a scrap of the same siding, cut out a square of that, and rotate it so the face of your cut piece touches the face of the existing siding, but upside down. This should complement the existing angle and give you a vertical surface. This should be possible as long as your siding has a vertical plane on the back and a consistent angle on the front (i.e. a triangular or trapezoidal profile).

If you do install a mounting block or cut the siding, make sure to waterproof any siding penetrations appropriately. Flashing might be ideal but given that your location is under a nice overhang, you may be able to get away without it. You may also want to use a piece of rot-proof material for this flat backing piece, such as cellular PVC.

Of course, the other option is to just accept that the fixture will be mounted at an angle, and choose a style where that isn't going to look bad. I think styles with a curved arm could be a good way to avoid drawing attention to the mounting angle:

enter image description here

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    Out of curiosity, from a brick-and-mortar EU resident, wouldn't the first solution compromise the water tightness of the sidings? Jul 12, 2023 at 7:27
  • I had not thought of cutting a square out of the siding to get to the vertical sheathing beneath; that seems like the "most correct" strategy so far. Thank you! Jul 12, 2023 at 21:43
  • What's your take on If I went with the second approach of mounting a wedge-shaped piece of siding flipped on the current siding to get vertical and then mounted the box on that — Could I conceivably get the same effect as the cut-a-hole-in-the-siding approach by cutting a hole in the wedge, the siding, and possibly the sheathing too and mounting a recessed junction box? Jul 12, 2023 at 21:48
  • @VladimirCravero the weather protection of the siding could be compromised if the new block were not installed, flashed, and/or caulked properly. For the original question, there's a lot of protection thanks to the overhang and most likely there is a house wrap installed behind the siding, so using a synthetic mounting block and caulking the top and sides should be adequate. It depends on the specific siding type and situation, so if you're not confident in how to approach this the "add a wedge" approach is safer in avoiding the risk. Jul 13, 2023 at 14:53
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Thanks to @ShimonRura I managed to finish this installation and was pleased with the results!

I took the advice of finding a piece of siding and flipping it to mount as a decorative block:

upside-down siding makes a vertical surface

Then I put a hole in that, and an electrical box in there (mounted to a stud behind the opening):

it takes a certain emotional fortitude to drill a 4" round hole in your house the hole now filled with an electrical box

Then, finally, mounted the light to the box and caulked it up: finished installation of light on siding

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