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I have a plaster wall and I'm looking to hang a floating shelf from it (no brackets). I have located the studs; most are 16 inches apart, and one is 13.5 inches from its neighbor. The shelf has three holes, 13.75 inches apart. The shelf came with mounting screws with thread that goes 1.75 inches from the tip. Although drywall anchors were included in the accessories, multiple reviews recommend not using them, and they are probably not right for my wall anyway.

I can easily arrange the shelf so that at least one of the holes aligns with a stud. Do I need anchors for the other holes not aligned with a stud? Or can I get by driving the screws directly into the plaster, with one screw driven into a stud? Thanks!

Edit: Here is a picture of the shelf and accompanying hardware:

enter image description here

User reviews mentioned avoiding the anchor that came with the product.

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    plaster can not hold anything. Use anchors. One stud screws is not enough, need minimum of 2
    – asinine
    Oct 17, 2022 at 23:47
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    Floating style shelves are basically the worst way you can put a load on a wall, so I wouldn't trust anything other than a solid bite into several studs, I would not trust any other kind of anchors.
    – whatsisname
    Oct 18, 2022 at 4:20
  • a few details please: size of shelf, intended load, type of "plaster" (gypsum wall board, a.k.a. drywall board, or plaster lath or ...?).
    – P2000
    Oct 18, 2022 at 4:21
  • @P2000 36" x 6" x .75" oak shelf, itself weighs probably around 5 pounds, anticipating a load even lighter (smaller plants, picture frames, etc.), the wall is plaster lath I believe.
    – Noah
    Oct 18, 2022 at 5:17

2 Answers 2

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You indicate (in a comment) that you have plaster and lath walls. In my experience, I've found P&L to be very strong and capable of supporting considerable weight, whether screws have gone into studs or not*. Personally, I would be comfortable simply driving the the screws into the wall and hanging the shelf directly off the plaster & lath.

If I understand correctly, you have 3 or more holes on your floating shelf, all spaced at 13.75". You also happen to have 2 studs spaced 13.75" while the rest are standard 16" spacing.

If this is correct, and since you do know where studs are, I would put two screws into the two 13.75" spaced studs and center the shelves on those studs. Then drive the rest of the screws to line up with the mounting holes in the shelf and hang it.

*I created an 8' tall x 8' long section of shelving supported by stanchions and shelf-support brackets that hung on a P&L wall for nearly 30 years. It was heavily loaded with books and papers for nearly all that time and never gave the slightest hint that it was going to fall. When I went to install it, I attempted to find studs, but a normal stud finder won't work through plaster & lath, so I just put up the stanchions and hoped for the best. The best happened.

I used stanchions like this (I guess maybe they're called "standards" or "uprights" - at least that's the term that came up at my local big-box):

Image of a wall standard for hanging adjustable shelving
Click to embiggen. Image courtesy of Lowes.com. No endorsement implied or intended.

I used drywall screws through the round screw holes directly into whatever they happened to hit behind. Some, I'm sure went into plaster only, others went through the plaster into lathe. One column's worth might have hit a stud, but since this house was built in the 1890s and has very hard studs, I don't think so - I don't have any recollection of having to work the drill too hard to drive them in. (No, no predrilling, no anchors, no nothing, just screws.)

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  • w.r.t. "simply driving the the screws into the wall" is that with plugs/toggle bolts, or bare into the lath? w.r.t "stanchions" there are different meanings (legs, wall strips, standing brackets...) could you clarify, perhaps with a pic?
    – P2000
    Oct 18, 2022 at 13:55
  • Hope that helps, @P2000. Probably not the most highly recommended method, but it did work for nearly 30 years until we replaced the shelves with enclosed cabinets.
    – FreeMan
    Oct 18, 2022 at 14:07
  • Thank you for this answer! It seems to disagree with some of the comments on the OP, though; do you know why there would be such vastly differing views on this?
    – Noah
    Oct 18, 2022 at 16:31
  • Per my previous comment, this isn't really recommended. I didn't know any better (well, yes, actually I did, but I didn't know any other way of finding studs), and it worked. There's no guarantee, @Noah that this will work for you. I do know that more than a few of my screws went into nothing but plaster, but that many didn't. Getting at least a couple of screws for your shelf into studs should be sufficient to hold the weight you expect.
    – FreeMan
    Oct 18, 2022 at 16:34
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    Shelves with stanchions or brackets are loaded completely differently than a floating shelf, so this comparison isn't appropriate. With a normal load, the bolts squeeze the bracket against the wall, and friction holds it upright, with virtually no shear or bending load on the fasteners. In the floating shelf, it's held up basically entirely by shear and bending forces. Instead of trying to pull the wall straight down, it will try to twist the lath out, and it's considerably weaker in that manner.
    – whatsisname
    Oct 18, 2022 at 17:57
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Screws for shelves are loaded differently depending on the mechanical arrangement of the bracketing.

If you have an L bracket (or shelf strip), the top screw of each bracket is loaded by pulling, and the bottom screws are loaded by a combination of press force and downward moment (a.k.a downward torque or moment force).

A floating shelf, that is without an L bracket but with cleats or rods, places a high moment load and pull force on the fastener, somewhat abetted by the thickness of the shelf. Fastening to a stud would be highly recommended to permit loading with anything more than the shelf itself and some light nick-nacks.

To mount such a shelf on lath & plaster you need to make sure that the shelf is thick enough and that the screws can withstand pull out from relatively brittle boards or underlying lath.

Toggle bolts are designed to withstand such pull out force.

If you hit lath, the toggle may not be necessary, and a simple screw might be fine. This would depend on the type and thickness of wood used for the lath.

enter image description here

If the shelf comes with its own custom screws, you could use expanding drywall anchors.

enter image description here

The more you load the shelf the more the plaster will be compressed at the bottom of the shelf. So the compression strength of your plaster will matter too.

If your sense of aesthetics and DIY skills allow, you could additionally support the back of the shelf with a strip of wood, perhaps 1/2in to 3/4in thick, as wide as the shelf but in height about 2x or 3x the thickness of the shelf, with the top of the strip aligned with the top of the shelf (and the rest thus below the shelf). This would reduce the gypsum or plaster compression and reduce the moment load.

In terms of static mechanical loads, glueing it to the shelf would be recommended to help reduce the moment load.

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  • Thank you for this! Unfortunately this hardware prevents me from using a toggle bolt. I uploaded a pic of the shelf and hardware. Sadly I have no idea what is inside my wall (but evidence suggests plaster and lath).
    – Noah
    Oct 18, 2022 at 17:03
  • If it's lath and plaster, it's almost certainly not gypsum, but lime-plaster.
    – Martin Bonner supports Monica
    Oct 18, 2022 at 17:03
  • @Noah with that arrangement you could use expanding plastic plugs. Updated.
    – P2000
    Oct 18, 2022 at 17:25

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