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using cedar to make mounting blocks for electrical fixtures on aluminum siding

using cedar to make mounting blocks for electrical fixtures on aluminum siding

Old 08-22-07, 05:16 PM
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Thumbs down using cedar to make mounting blocks for electrical fixtures on aluminum siding

I am having my 25 yr old aluminum sided house painted. Of course, with new paint, I just can't keep the same old cruddy exterior lights (or so my wife says).

We purchased new lights, and their mount is taller than the lap of the siding.
Rather than mount the lights with a huge gap behind, I set out to find a suitable mounting block.

I looked for the vinyl molded mounts that most 'big box' HW stores carry. These mounts have the siding lap cut into them so they fit tight against the siding, eliminsting gaps for critters like bees to build nests. They also provide a nice flat mount for the fixture. After searching the stores near me, none of them has the lap I need (they offered either 4" or 5", I need 3 3/4") nor the height.

Being handy with finish carpentry, I am considering making my own out of cedar, primarily because I've heard that cedar is incredibly rot resistant, and great for outdoor projects. I've tried building outdoor 'stuff' out of conventional woods and coating it with house paint, but I wind up having to donate said stuff to the local landfill within a relatively short time.

I plan to use dried cedar planks, and paint them the same color as the house.

I live in the northeast, hence we have a cold winter. Is there a way to seal cedar to prevent moisture from infiltrating the wood, freezing, and possibly splitting the block?

After reading other posts, I see that I should use a good oil-based primer. Then I'll probably use the same latex as on the house. I wonder if this would provide a good enough seal. Anymore advice here would be appreciated, too.

Lastly, does anyone have a better idea?

Thanks in advance...

Old 08-22-07, 05:40 PM
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Sounds like you have the right idea. Slightly round all sharp edges with sandpaper and prime and paint all 6 sides so as not to leave any edge unpainted. This will reduce the amount of expansion and contraction of the wood since it will be less prone to absorb moisture.

With aluminum siding, you'll probably want to cut out the aluminum siding with a 4 1/2" grinder and a 1/16" thick metal cutting abrasive blade, so that your cedar block can sit flat against the sheathing. Once your prepainted mounting block is installed, you'd caulk around it to seal it to the siding, then once the caulk has set up, you can paint it too.

I like it when the mounting block is symetrical with the lap of the siding... either centered on the bottom edge of the siding with equal amounts of the mounting block above and below that edge... or centered on the full reveal of one course so that the mounting block extends above and below one full course by the same amount.

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