Hanging a heavy mirror/cabinet on a tiled dot & dab bathroom wall

DaveyH · 8 Oct 2015

Hi,

We have just bought a fairly big and heavy mirror/cabinet to go in our not yet finished new bathroom (it's 500mm x 700mm and weights 20kg).

However, I'm worried that our skimmed dot and dab plasterboard walls won't be strong enough to support it.

As I haven't actually started the tiling yet, I was wondering if there are any better options than being forced to use these http://www.screwfix.com/p/grip-it-assorted-plasterboard-fixings-32-piece-set/6165j or these http://www.drylinepro.com/ or some other fancy type wall plug?

The only idea that I can think of, is to cut out a letter boxed shaped hole in the plasterboard an inch higher and an inch lower of where I estimate the bracket will end up going, then fill that hole with bonding plaster until it's back level with the plasterboards. I could then use the normal 40mm rawl plugs that came with it. Does this sound like a reasonable idea, or is there a much better way of adding some strength to a dot and dab wall for hanging heavy items?

Here is a picture of the actual bracket against the skimmed dot and dabbed wall (remember though, there will be tiles going over the dot and dab).

The mirror/cabinet was supplied with these normal looking 40mm rawl plugs.

(PS. Whatever I end up doing, as a bit of extra back up, I will definitely be adding a smear of grab adhesive to the back of the bracket so that it's also stuck to the tiles as well as screwed into the tiled wall somehow).

Thanks in advance.

Burnerman · 8 Oct 2015

Personally I'd forget about those plasterboard fixings, clever though they are.....I'd go for a traditional 8mm rawlplug that would pass through the tile, plasterboard and into the wall behind.
John

bernardgreen · 9 Oct 2015

The problem is when you tighten the scew the cabinet is pressing onto the plaster board which maay crack.

Cut a hole in the plaster board where each screw will be. Then use a spacer between the brick ( or block ) work and the back of the cabinet.

A piece of wood 2 inches square with a screw hole drillef in the centre should be more than adequate. Make the spacer thick enough that it comes just above the surface of the plaster board. The spacer than takes the pressure of the tightening screw and not the plaster board . It will also stop the screw bending under the weight of the cabinet and it's contents.

foxhole · 11 Oct 2015

Agree with burnerman, the tile will spread the force so no cracking.

DaveyH · 11 Oct 2015

Cheers for all the replies chaps, but I still recon my own idea of chopping out a section of plasterboard and filling the hole left with plaster is still the best idea so far, and I will demonstrate why with a couple of cross section diagrams of a rawl plug when it's in the wall.

The supplied rawl plugs are 40mm long and have an 8mm diameter.

My idea.

Rawl plug held in 7mm of tile, 3mm of tile adhesive, 20mm of plaster and 10mm brick. The only weak point is the 3mm of tile adhesive.

Doing nothing

Rawl plug held in 7mm of tile, 3mm of tile adhesive, 15mm of plasterboard, 5mm of air and 10mm brick. Weakpoints 5mm of air, 15mm of plasterboard and the 3mm of tile adhesive.

Surely the 20mm of plaster will be a lot stronger than 15mm of plasterboard and 5mm of air?

PS. I appreciate my idea will be no good for a tradesman out in the field, because it would waste a couple of hours of your valuable time and it would also be impossible to do after the tiles were up.

cheers

Burnerman · 11 Oct 2015

Plaster is the worst possible medium for holding rawlplugs......the tile will grip the screw well enough and make the plaster redundant.
The best solution is to have a plug thats long enough to penetrate right through into the brickwork and use a screw to suit that.
Personally I bin the plugs and screws that come with fixing kits as a rule and use my own Fischer gear.
John

DaveyH · 11 Oct 2015

Burnerman said:
Plaster is the worst possible medium for holding rawlplugs......the tile will grip the screw well enough and make the plaster redundant.
The best solution is to have a plug thats long enough to penetrate right through into the brickwork and use a screw to suit that.
Personally I bin the plugs and screws that come with fixing kits as a rule and use my own Fischer gear.
John

I agree plaster is pretty weak, so instead of using 20mm of plaster what about using say 18mm of mortar with say 2mm of plaster on it to skim it level with the plaster boards, so the cross section would be like this?

Burnerman · 11 Oct 2015

You're relying on good adhesion between the brickwork and your dab of mortar here......I'd still use a plug that penetrates deeper into the brick, and use a screw that would reach into the brick too. If the cabinet was exceptionally heavy, only this method would do.
John

bernardgreen · 11 Oct 2015

How thick is the back of the cabinet ( or the bracket that goes onto the wall ) as that will take up some of the 40 mm of the screw's length.

I would not trust a mere 10 mm of plug and screw in the wall to hold a cabinet that weighs 20 kg. Add a few more kg for the things that are put into the cabinet to get the real static load. Then consider the dynamic forces from cabinet doors pulled opened and slammed shut. These are horizontal forces pushing and pulling on the fixings.

I doubt very much that the 10 mm of plug and screw in the wall remain firm for very long. The plaster and tile will probably stop the cabinet dropping straight down put will do very little to hold it if someone pulls it away from the wall. With the cabinet door(s) open then the bottom will be pressed against the wall and the top will be pulling away from the wall.

Drill at least 20 mm into the brick work, push the plug fully into that 20 mm and then use screws long enough to go 20 mm into the brick work.

Take into account that a child may pull on the cabinet to try and reach something in it. If the fixings fail then the child could be injured.

rsgaz · 11 Oct 2015

Or just use these rigifix fixings...

Gaz

DaveyH · 11 Oct 2015

bernardgreen said:
How thick is the back of the cabinet ( or the bracket that goes onto the wall ) as that will take up some of the 40 mm of the screw's length.

That wouldn't be an issue. The supplied screws are actually 50mm long, the supplied rawl plugs are 40mm and the 2 supplied metal brackets are about 2mm thick. The top bracket is held by 3 screws and is hidden by the cabinet. The bottom bracket is visible (if you stooped down) and held by 2 screws.

Here is the manufactures diagram.

http://www.illuminated-mirrors.uk.com/pdf/K353.pdf

DaveyH · 11 Oct 2015

rsgaz said:
Or just use these rigifix fixings...

Gaz

They look really good. The only issue I can see is the lip on them, which would mean they ended up being 1 or 2 mm proud of the tiles, which would mean the brackets would also end up 1 or 2 mm proud of my tiles (stop the video at exactly 3 mins 5 second and you'll see what I mean).

DaveyH · 13 Oct 2015

Burnerman said:
You're relying on good adhesion between the brickwork and your dab of mortar here......I'd still use a plug that penetrates deeper into the brick, and use a screw that would reach into the brick too. If the cabinet was exceptionally heavy, only this method would do.
John

I agree, a longer plug and screw is the best overall solution in my situation, but if I was to chop out a hole in the plasterboard and fill the hole with mortar, is there something that would help the dab of mortar adhere to the bricks (like how PVA helps plaster adhere to bricks)?

Burnerman · 13 Oct 2015

No doubt some PVA would help adhesion to some degree, but it's only where the mortar has a large surface area when it is particularly effective.
Just go for a longer plug....the job will be fine, I'm sure.
John

opps · 15 Oct 2015

I too would just get longer fixings.

Do not be tempted to drill deeper and push the provided plugs deeper in to the wall. As you tighten the screw the plug will just pull its way up the thread.

Another alternative is make a note of where the dots are and re-drill the metal support plate so that you end up getting fixings where the dots are.

diynot

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Hanging a heavy mirror/cabinet on a tiled dot & dab bathroom wall

Similar threads