Hung a shelf on a plaster wall, and it fell, but I want to try again--how do I do it right?

Question

I hung 6 Ikea shelves (these ones, which are metal L-shaped brackets with wood shelves on top) on plaster walls using medium-duty plastic anchors.

It was a real issue while we were working. The building was built in the 60s and the wall I'm using appears to be entirely plaster with no studs, no lath, nothing (as far as I can tell). Just solid plaster all the way through.

On the 6h shelf, we thought we'd found a stud and didn't use an anchor. Turns out whatever that was it wasn't a stud. 5 of the 6 are still up after about 2 weeks, but the 6th has fallen.

Ideally I can put the shelf up in the same spot. What I would like to do is fill the holes with spackle (or something else?) and push a masonry anchor into it before it sets, then re-hang the shelf. Is that insane?

If it is insane, can I just cover the holes, move the shelf over an inch, and try again with masonry anchors this time?

Edited to add some pictures:

Answer 1

The ideal solution would be to use studs. They are most likely there, but they are difficult to find on plaster walls. I've had the best luck with a magnetic stud finder on my plaster walls. Regular electronic stud finders seem to be worthless here (at least the ones I've tried).

IKEA stuff tends to not be built for standard 16" stud spacing though, so most of the time, this doesn't work anyway. It also limits where you can put things if you want things aligned/centered etc. Another solution then might be to open up the wall and add some blocking for your shelves. This is obviously very involved and messy.

Since the holes have already been enlarged, it seems that they might be large enough now to use a better anchor here. I would recommend a toggle bolt. They usually require a pretty large hole anyway to get them through initially. They're also kind of a pain to work with, but they do hold very well. But you would still want to limit what you put on these shelves. Picture frames are probably OK, a shelf full of heavy cook books might be pushing it.

Image: Tenbergen at English Wikipedia, Toggle bolts, CC BY-SA 3.0

Answer 2

You must figure out how your walls are built. There is an anchor for everything. No wall is just plaster or just drywall. Something stronger is holding it up.

It's either a stud wall, either wood or metal studs, with one or more layers of things on it. Could be as thin as 1/2 inch drywall or as thick as two layers of drywall over old cracked plaster over fiberboard. Or it's a solid wall .... brick, hollow block, solid block, poured concrete .... with plaster over it, and who knows, maybe with drywall on top of that. You never know.

To put up a shelf like that you HAVE to figure it out, you HAVE to figure out how thick the plaster/drywall coating(s) are, what is behind them, and how to get to the actual wall structure (stud, brick, whatever).

Once you've done that:

• Wood studs: Use wood screws, long enough to penetrate at least an inch into the wood after getting through the shelf bracket and all layers of plaster/drywall.
• Metal studs: Self tapping sheet metal screws (same proviso about length) or toggle anchors
• Brick or block: masonry anchors, into the masonry, with long enough screws that you're not relying on the plaster for anything.
• Concrete: Tapcon screws

An alternative approach would be to buy floor-standing shelving from Ikea, or buy wall-mounted shelving from a Canadian/US retailer where you'll get long metal rails that can be screwed to the wall in 4 to 6 places EACH RAIL, and then even if you use crappy anchors and don't do a good job with them, the shelves will probably stay up. Maybe.