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Hanging A Heavy Mirror

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MTbowels | 07:42 Sat 16th Oct 2021 | Home & Garden
7 Answers
My daughter has asked me to hang a large mirror in her bedroom. The mirror was bought in IKEA and is called a Toftbyn mirror. It's 75cm wide and 165 long including the wood effect frame all around, mitred at the corners and is full length in the sense of a dressing mirror.
The mirror is to be attached to a plastered wall. At the back of the frame there are strips of steel about 75mm x 40mm screwed diagonally across the mitred corner. The long edge of the strip has small serrations along its length on the inside edge.
From the vague instructions, it seems I'm meant to screw two round head (not countersunk) woodscrew into the wall 60cm apart and hang the mirror by simply resting it on the screws ie the serrations on the metal strip will catch on the screw.
I'm not happy about this given that the mirror weighs 15kg. I was thinking of shield anchors (the type with a bolt head) but the screwed shaft would be too big to catch on the serrations although that might be irrelevant. Round head screw aren't available in big sizes such a No 12. No 8 round head screws wouldn't take the weight in my opinion despite the instructions showing screws of about that size - there are no recommended sizes mentioned.
I'd there another means of hanging the mirror preferably without anything been seen above the top edge of the mirror on the wall?
Thank you.

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Well the shear strength of a no. 8 is 89lb so two would be ample but if you want to go to 12s they are available https://www.spaldingfasteners.co.uk/no-12-a2-stainless-steel-round-slotted-head-wood-screws/
well I think it is something I could see myself doing

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I think you may be worrying about the wrong thing, MT.
Round-head (or dome-head) definitely, but I really don't think an 8 or a 12 are going to jump out of their slot.
If both brackets are diagonal, then the weight of the mirror is going to drive the screws into the slots securely.

As Fitzer has pointed out, the screws will never fail under 15kg.
I'd be much more concerned about getting a good fixing in the substrate of the wall.
What matters most is: stud wall? masonry? cob?
Question Author
Thank you all.

The Builder, the wall is your common or garden red brick wall made of standard bricks and mortar. Fitzer mentioned that the shearing figure for no 8 screws was 89lb - I just thought that a no 12 would be that much stronger and unlikely to snap under the weight. I'm not quite following how these flat pieces of steel with a serrated edge can keep a 15kg mirror from falling off the wall. Surely that much pressure on the screw shank can't be good for the screw?
The rawlplug plastic wall plugs I intended to use are about 35mm long and will take a no 12 woodscrew. I started thinking of rawlbolts as I wasn't sure if such a plug and screw could support the weight, with only 35mm of the screw in the wall.
Question Author
It's an upstairs external wall on a detached house, plastered on the inside and rendered on the outside - no neighbours to disturb while drilling!
The only way a screw could sheer in this situation would be if it were subjected to a "dynamic" load. i.e. a moving load such as repeatedly jumping up and down on it.

You have a "static" load. No movement. By all means use no12 screws if you're concerned.

The fixing is by far the more important consideration. You really don't need Rawlbolts or any kind of anchor bolt. Anchors are really for much heavier applications, such as fixing timber to a wall to carry floor joists. Joists are subject to traffic since you walk around on them. Walking traffic can cause the joists to bounce and creep. So a heavier fixing is needed.

Re: the brickwork.
If it's an older house, avoid fixing into the horizontal mortar joints. It may well be lime or at least very old mortar.
The distance between horizontal joints (vertically) is 3" in old brickwork.
Locate a spot behind where the mirror is going (so that the mirror hides it) and poke about until you can identify a horizontal mortar bed.
By measurement, draw a pencil line 1 1/2" up from the bed. You're now halfway up a brick. Drill on this line.

Vertical joints are 9" apart (horizontally). Similarly, avoid these when drilling.
When you have two holes marked that are smack in the middle of a brick each, then drill.
You've got your plugs. I would suggest screws of around 70-75mm length. (Make sure you drill deep enough to take the length of screw.)

Plugs for a no12 screw can carry a load up to 50kg (each).
Get your fixings right, and it'll be solid forever.
Question Author
Thank you The Builder. You've provided some great advice and I'll do as you suggest.

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