Been searching around and I have more questions than answers. I'm not sure what kind of stucco it is, but it is very smooth. The mailbox is a little heavier than you might expect (maybe 10-15 lbs).
Before doing any research I figured I would drill with a masonry bit and use some sort of anchor intended for stucco, and that would be it. Unfortunately I am finding lots of contradictory information:
- some things say to use a plastic anchor, some say never to
- some say that the following photo is a stucco anchor, while some say it's a drywall anchor:
- some say that I have to have a particular type of stucco
- searching for stucco anchors at Home Depot, for example, just brings up different types of screws meant for concrete (some of which actually say "anchor" right on the package even though they are screws and not anchors - so maybe anchor doesn't mean what I think it does?)
- some things say to use some kind of silicon sealant in the hole I drill, others make no mention of this
I did experiment a bit in an inconspicuous location and using a cement screw didn't work well at all (I drilled a hole with the bit size the instructions said to use, and the screw was completely loose). Using the drywall (?) anchor above seemed to be very secure but it really chewed up the stucco as I was screwing it in (I drilled a hole first but just guessed at the size).
What's the best approach here and why is there so much contradictory information out there?