this post was submitted on 04 Mar 2025
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I’m planning to make some floating shelves 150 cm wide and 30 cm deep.

I want to mount them on a wall that has a plasterboard of thickness 13mm behind which is a plywood backing of 15mm according to the details provided by the contractor (see the attached image). This construction was apparently intended for hanging TVs and they recommend using wood screws that are not longer than 30mm.

One of the shelves will have my record collection which could weigh between 25-50kg. What are some options for hardware I can use to mount the floating shelves?

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[–] Onomatopoeia@lemmy.cafe 11 points 4 days ago* (last edited 4 days ago) (1 children)

I wouldn't use wood screws for that kind of weight on a floating shelf (even with that nice ply backer). A floating shelf has a lot of leverage against that screw, trying to pull it outward, while other shelf types pull straight down with less lever action.

Use something like a toggle bolt or Molly. They distribute the load a lot more. I really prefer Molly for plaster/sheetrock, because they stay in place. Perfect for a floating shelf.

Edit: I hope the shelf has 3 or 4 mount points. That's still a lot of weight for just 2 screws with a floating shelf. I'd be concerned about the screw heads handling the load over time. They're probably fine, but it only takes one poorly made screw to bring the shelf down.

[–] colourlessidea@sopuli.xyz 4 points 4 days ago (2 children)

Thanks for the info! Since I’m making the shelf, I can put more mount points so that should be no problem.

However - the problem with the Molly bolt things will be that the left half of the wall has space for a pocket door behind it so I’m worried that the toggle/molly bolts will get in the way of the door.

Maybe I should throw away the floating shelves idea…

[–] Onomatopoeia@lemmy.cafe 4 points 4 days ago* (last edited 4 days ago) (1 children)

Yea, the pocket door is a challenge, but there should be plenty of room - there should be a lot of space from the door to the ply panel. Once installed, a Molly should only extend about 1cm. Just make sure to cut the screw down once installed (the screw is longer so it can compress the Molly, easy to cut with a pair of dikes).

Optionally, you can use a wood screw for that end, one that's long enough to just go through the ply when set at the right depth. This will ensure you have maximum thread engagement.

Wood screws will probably be OK, it just makes me a little nervous with that weight. Of course, more screws=more distributed load, but then you have to get them all to line up perfectly, which isn't easy.

[–] colourlessidea@sopuli.xyz 3 points 4 days ago (1 children)

I think you’re right! I just checked and the pocket door is definitely much further behind.

Now the question is - how exactly do I use these to mount the shelf? Is there some sort of hidden bracket I can buy?

[–] RvTV95XBeo@sh.itjust.works 3 points 4 days ago (1 children)

Lots of ways to do it, the most common I've seen are like this:

https://www.ultrashelf.com/collections/floating-shelf-brackets

Where holes are drilled into the shelves and then they're slid onto the rods screwed to the wall. Hard to level but looks great if done right

[–] Onomatopoeia@lemmy.cafe 1 points 2 days ago

Wow, 50 lbs (~20 kg) per stud, with a bunch of screw holes in the base plate. Problem solved, and you could just use a number of wood screws into the ply panel, just spaced well apart (like 2.5-3 cm), and anchor into a stud where you can with a long lag (3"/~8cm).

Or if you can only hit a stud on one side, use a single Molly on the other and a couple wood screws in between.

[–] buwho@lemmy.ml 2 points 4 days ago

yeah you may want some sort of "leg" running back to the wall, like a right triangle. that way the weight is not ONLY pulling straight outward, it has a a leg that presses back against the wall for support.

Don't put a record collection on a floating shelf.

It's a bad idea.

[–] buwho@lemmy.ml 4 points 4 days ago (1 children)

i wouldnt put too much weight or leverage on that shelf. the sheet rock is basically doing nothing and plywood, depending on the quality and with that thickness is not much to grab on to. are there no studs you can hit? depending on how many screws you are able use, i would potentially use GRK brand cabinet screws, if you can find them. theyre some of the best in the business as far as bite and sheer strength. if you can do a longer horizontal run like a ledger you can distribute alot of the load across the wall, instead of on a few points only...my tv mount is designed to hit studs with like 2 1/2" lags...way burlier...but i would consider grk cabinet screws. what is keeping the whole wall from flexing under weight though?

[–] colourlessidea@sopuli.xyz 2 points 4 days ago (1 children)

Your last question is a good one. I have no idea - I’m pretty new to this stuff. What is normally used to keep a wall from flexing?

[–] Telorand@reddthat.com 5 points 4 days ago (1 children)

Studs. No, seriously. I have floating shelves that hold stacks of ceramic plates and bowls, and I made sure to screw into as many studs as possible.

If you can't, and sometimes you can't, I recommend using these drywall toggle anchors. They've been fantastic. When I couldn't find a stud but wanted more support points on the shelf hangers, I used those. Note that I do recommend marking the orientation of the toggle on the head of the anchor, because you'll want it to be as vertical as possible.

[–] colourlessidea@sopuli.xyz 1 points 4 days ago

Ah gotcha. Well I’m pretty sure there are studs on the right half of the wall (the left half has space for a pocket door). I think there are two but my stud finder is not very good and I’m not sure if they’re wood or metal studs.