I'm building some flower boxes to go under my windows. I made them from cedar and plan to use L brackets for mounting. My wife is excited and keeps telling her parents about the project, but they're really concerned it could damage our Hardie siding. I plan to use stainless screws, keep the boxes about an inch away from the siding, seal the pre-drilled screw holes with caulk, and drill holes in the bottom for drainage. Am I missing anything? Should I genuinely worry about ruining my siding?
2 Answers
You're on the right track with keeping a one-inch gap to avoid trapping moisture against the siding. Just ensure you hit the studs behind the siding when mounting. If you want extra caution, consider adding stainless or polypropylene spacers behind the L brackets to give it that additional distance!
That one-inch gap should help protect your Hardie siding. However, wood like cedar can eventually rot. Consider using plastic plant pots inside the cedar boxes to help avoid that moisture issue altogether. It’s a simple fix that could prevent any future headaches!

I get the idea, but plastic breaks down over time too and creates a mess. It might be better to use stainless steel for the boxes! Just make sure to use the same grade of stainless for the bolts to avoid corrosion. Aluminum could also be a lightweight option, but it’s tricky to work with if you're not familiar. Just throwing that out there!