Walls – How to fix flexible stucco

I'd agree with the masonry bit (as well, stucco is rough on drill bits anyway) of whatever size is recommended for the wall anchors you're using.

I'd been reluctant to post a response, as I had no idea what do do for the wall without flattening down that section, but I have a completely untested idea --

If the stucco isn't too extreme in its texture, and you're not going to be putting lots of load on the shelf, you might be able to cut a piece of foam to use as backing, and then tighten it to the wall to compress the foam so it's not too bouncy. You're likely going to want extra (or heavier) bolts for this; there won't be friction against the wall, so the bolts are going to be taking the whole load in sheer. Also, you won't have the same support against moment.

I was thinking some of the stiffer spray-foam might work, but if you wanted to make it removable without damage (and if you didn't, you'd just flatten the wall), you'd need to add some release agent, which might stain the wall, or go through some hoops to pull this off:

1. Make a frame the size of the bracket, open on the side against the wall, and an extra hole (see below).
2. Figure out where you want to mount the bracket.
3. Tape a plastic bag large enough to full the frame on the end of a can of spray foam.
4. Stuff the bag in the frame through the hole.
5. Hold the frame where you want to mount the bracket, and inject the spray foam.
6. Wait for it to set up.
7. Repeat steps 2 through 6 for each additional bracket location.

You might be able to do something similar with other products to mold to the wall, but all of the ones I can think of have slower set times which would make it really slow going.

Based on other Googling, I found I had two choices: big holes through the stucco, plugged with silicone caulk and screw anchors (if I needed to hang something heavy, I definitely would go that route) or Loctite Stik'n'Seal Outdoor Adhesive.

So I Stuck'n'Sealed 'em. Note to anyone who goes this route: it seems to take FOREVER for the glue to set! If I had this to do again I would definitely invent some sort of rig to clamp them to the wall while the glue sets. Also, one of the digits ended up in a very uneven section of stucco; the lower two-thirds are flat against the wall, while the top is about 1/8th" proud. I'll definitely need to go back to that with sealer...

However, for the time being... so far so good. If anyone else has a similar problem, this is what I'd recommend.