Fixing a mirror to the wall - what size screw?

kerri_gt

Hoping folks can offer a bit of advise as I definitely don't want the thing falling off the wall and having 7yrs bad luck 
I have a rectangular mirror with 4 pre-drilled corner holes which I would like to put up on a wall but need some advice on the most suitable size / gauge screws to use (the mirror was previously on a studio wall before I bought it)

Mirror Size approx. 50cm x 110cm

Existing holes approx. 5mm diameter

Weight of mirror approx. 8kg

 The wall itself appears solid – either brick or most likely clinker block as it’s a solid internal wall between two rooms. Deff not a stud wall though.

I was looking at these screws but unsure on the gauge and length that would be most appropriate and hoping someone with experience could offer some guidance 

https://www.tcfixings.co.uk/main/product/productinfo/1466/8G-x-50mm-Countersunk-Mirror-Screws-BZP-5BA/1
(I do know I need to order bushes too so the mirror doesn't crack) 

FreeBear

One normally aims for 25mm of screw engagement in brick for maximum strength. So for a typical wall and say a mirror of 5mm thickness and 12-15mm of plaster, 45-50mm would be about right. When you drill the holes in the wall, clear out the loose dust and then press the wall plug in so that it goes in beyond the plaster. When you come to drive the screw in, the plug will expand in to brick rather than the plaster - This stops the plaster from taking the weight of the mirror and possibly breaking up around the hole. Don't over-tighten the screw, and you should be set to go.

kerri_gt

Thanks Freebear, good tip about the plaster / plug too. I'll measure the mirror thickness too but sure it's  pretty average depth. Another of those lockdown jobs on the list (and the fact the mirror has been propped against the wall since we moved 4yrs ago...and several years before that in our old house too)

daivid

Hopefully you will have done so already but before you start drilling consider the possibility of there being wires/pipes in the wall. Unless you know exactly where the pipes and wires are in your house you could be surprised.

kerri_gt

daivid said:

Hopefully you will have done so already but before you start drilling consider the possibility of there being wires/pipes in the wall. Unless you know exactly where the pipes and wires are in your house you could be surprised.

The wall is where i think the old hot water tank used to be. It backs onto the bathroom but theres no plumbing on the other side. The wiring helpfully / unhelpfully depending on what we're trying to do at the time is all in conduit and most of the central heating pipes weren't chased into the walls when it was installed.  That said we'll prob now find something random in that wall, tis the way with this house. 

531063

A 6 mm drill bit with red plugs & a size 8 screw should be ok

Mutton_Geoff

You don't need to go into the wall much more than 25 or 30mm since the force of the mirror mounted on the wall will be acting straight down (ie a sheer force). The mirror will not be acting to pull the screws out from the wall, only to try to slide down the wall. For that reason, there is no need for overkill.

Remember when you tighten the screws to not tighten them up, you'll crack the mirror. Stop screwing as soon as they reach the mirror glass, do not tighten!