Resin is obviously a great way forward as it holds well without creating stress, but it’s much more work and the nuts don’t look as neat as a screw or bolt head. Don’t forget that the weight is mostly in ‘shear’ too; i.e. it’s trying to pull down on the fixing and not too much force is trying to pull the thing out of the wall! Difficult without knowing the weight of the mirror, but I’d have through that an 80mm slotted, square hook would be fine with a regular brown 7mm plug, making sure that you push the plug into the masonry itself and through the plasterworks.

How deep does a wall plug need to be? I talked about this a lot on another post, here’s the link: How to Properly Use Wall Plugs See what they have at the store screw/length wise, stainless steel is best of course. You could even consider structural timber screws, if you can get a wall plug big enough for them. They are long, have flanged heads and designed for outdoor use, just a thought (Have a look at what I mean at screwfix…). Hope that gives you an alternative and I really must write up this tip into an article (so thanks for that push!) Any mirror that needs more than this should be hung on a pair of hooks in my opinion (gives better leveling too).Can I first ask what you are fastening to the wall? It’s just that plastic wall plugs of the size you’d need for a screw that size are not in common use. Sure you can buy ‘sets’ of big screws that come with a large plastic plug (sink/washbasin screws to name one) but usually if you’re hanging something heavy on a masonry wall you’d use a ‘rawlbolt’ style expanding bolt; either a hex head and washer or a nut and washer. By coincidence, the size of an imperial screw head also roughly equates to the gauge. For example an 8-gauge screw has an 8mm wide head…..handy huh? It depends more on the diameter or gauge of the screws shank really. You might find that a large plug like a 70mm one is designed for a really large diameter screw (5 or 6mm plus).

I’ve explained this screw data in an easy to understand table because I find manufacturers recommendations are often vague and general, I mean; why not be specific? I understand there’s a ‘range’ but why not give us the ‘ideal’ measurement, because mostly we have a choice?

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Let me know what you’re fixing up and clarify the shank diameter of the screw and I’ll be much more specific, I promise!