DIY Related: Tiling over large mirror

[PeterSandhurst]

New to this forum and first post

25 years ago I tiled my family bathroom. The cement and tiles are still rock hard and having tried (and failed) to remove a few without doing immense damage to the plaster beneath I shall tile over them.

My problem is a mirror.

I have a heavy duty 3 foot by 2 foot mirror inset into the tiles with the same surface level. Assuming I can get the new layout to make use of the mirror I will try to keep it but chances are it will have to be covered.

Question is this :

- I cemented the entire back of the mirror to the wall as I did with all tiles. It is solid as a rock. Can I tile over it directly? If so, does it need scoring as if it were a glazed tile? And finally, what adhesive would I use for tiling onto glass?

Many thanks in advance for your time

Peter from Sandhurst UK

[jwatson]

i have never done it but i think a spatter dash coat/slurry coat (acrylic primer and rapid set mix) over the full area including tiles will help adhesion as this method was taught to me as being the solution to tiling over any shiny/smooth surface. hope this helps.

[Colour Republic]

If your not superstitious you could smash the mirror out then bring the hole level with a skim of rapid set adhesive

[PeterSandhurst]

My thanks to you both for prompt replies.

If your not superstitious you could smash the mirror out then bring the hole level with a skim of rapid set adhesive

I have no superstitions, but the real problem is that this very thick mirror will hang on for dear life and the resulting mountain of glass shards will be a nightmare to work with and clear not to mention the plaster that it will take with it (if the first 8 tiles are anything to go by.

I will defo try to go over it if I cannot reuse it so if anyone has first hand experience that might build on the useful comments above I would be keen to hear from you.

[jwatson]

My thanks to you both for prompt replies.



I have no superstitions, but the real problem is that this very thick mirror will hang on for dear life and the resulting mountain of glass shards will be a nightmare to work with and clear not to mention the plaster that it will take with it (if the first 8 tiles are anything to go by.

I will defo try to go over it if I cannot reuse it so if anyone has first hand experience that might build on the useful comments above I would be keen to hear from you.

The method i have stated will work, just make sure the tiles/mirror are well secured. you need to take into account the weight issues of tiling on top of tiles. it can be done but there will be a higher stress on the wall. in an ideal world the tiles should be stripped off. i know this is a problem for you as they are well stuck. i would advise working out what adisional weight in tiles, adhesive, and grout you will be fixing plus an estimated weight of existing tiles already fixed and use this guide i have aquired to make an informed desision of what next to do.
1. Substrate weight ratings

A common question, how much weight can my wall support, here are the recommended max weight ratings in KG / m2

Plaster Skim on Plaster Board........20KG
Skim and Set Plaster...................28KG
Plaster Board.............................32KG
Sand and Cement.......................40KG
Cement Backer Board..................55KG
Hardibacker Board.......................45KG
Lightweight Tile Backer Board........40KG
Glass Reinforced Cement Sheet.....50KG
Gypsum Fiber Board.....................40KG

Remember to factor in the weight of the tile / m2 AND adhesive and grout
2. (Some adhesives are manufactured as lighter products).
3. Grout weight will also depend on how large the tiles are that you are using and the thickness e.g. a tiled area that uses 300mm tiles will have more grout than an area with 600mm.

Grout.........2KG / m2
Adhesive....4KG / m2

[tilerjason]

smash it and start from fresh piece of mind then, plus you have to take into account the weight of the old and new tiles and adhesive and what there originally stuck to plaster board has a max weight load of of 32 kg per sm and plaster is 20 kg per sm.


dare you to knock it off lol and dont forget to take some pics and post them on here

[tilerjason]

The method i have stated will work, just make sure the tiles/mirror are well secured. you need to take into account the weight issues of tiling on top of tiles. it can be done but there will be a higher stress on the wall. in an ideal world the tiles should be stripped off. i know this is a problem for you as they are well stuck. i would advise working out what adisional weight in tiles, adhesive, and grout you will be fixing plus an estimated weight of existing tiles already fixed and use this guide i have aquired to make an informed desision of what next to do.
1. Substrate weight ratings
A common question, how much weight can my wall support, here are the recommended max weight ratings in KG / m2
Plaster Skim on Plaster Board........20KG
Skim and Set Plaster...................28KG
Plaster Board.............................32KG
Sand and Cement.......................40KG
Cement Backer Board..................55KG
Hardibacker Board.......................45KG
Lightweight Tile Backer Board........40KG
Glass Reinforced Cement Sheet.....50KG
Gypsum Fiber Board.....................40KG
Remember to factor in the weight of the tile / m2 AND adhesive and grout
2. (Some adhesives are manufactured as lighter products).
3. Grout weight will also depend on how large the tiles are that you are using and the thickness e.g. a tiled area that uses 300mm tiles will have more grout than an area with 600mm.
Grout.........2KG / m2
Adhesive....4KG / m2

just beat me with this post lol

[jwatson]

sorry pal we must have both submited at same time lol.

[tilerjason]

ill let you off lol hows the mosaic job going

[Dave]

The mirror has a backing that provides the mirror finish and that is all that is holding that in place, IMO you should not tile over it..

The weight of the new tiles will deffo exceed the weight for that substrate.. if you tile over then that is your choice but not one that i can recommend

[jwatson]

not started that job i was talking to you about. concrete sub needs a few more weeks to cure. will get you some good pics when i have finished it.
are you in kingcraig next week?

[jwatson]

The mirror has a backing that provides the mirror finish and that is all that is holding that in place, IMO you should not tile over it..

The weight of the new tiles will deffo exceed to weight for that substrate.. if you tile over then that is your choice but not one that i can recommend

cheers for that info dave, never tiled ontop of a mirror before and wont now. so simple when you think of the backing finish it has.

[PeterSandhurst]

This afternoon, after reading the 'mirror backing substrate' reply, I ran a test on a piece of 15in square mirror and secured it to a plank using silicon mastic and slung it from the underside of an RJS in my garage. I then secured another board (laminate) to the other face (glazed side) using silicon mastic again and screwed three eyehooks into the laminate. I then hung 46kgs of Pavia blocks from each eyelet in builders buckets giving a total strain of roughly 140kgs on the backing and it is still hanging there now 4 hours later. The messy job didn't cover all the backing so the figures above are understated amd better than shown but you get the idea.

Not sure what that comes to in per square meter calculations but it sure as hell gives me the confidence to tile over the big beasty mirror in the bathroom as the tile weights are a very small fraction of that.

If I do, and it fails, I will be back to share. Otherwise, assume I did OK and thanks to all for their input, much appreciated.

Best

Peter

PS - Selling strong 15" square mirror, slightly used /marked

[kilty55]

all the best with your job peter

[widler]

i don't think your problem wil be the mirror holding on the wall,the problem will be the weight issue with your slurry sticking to the very shiny surface of the mirror,the adhesive on the slurry and the tiles on top of that.thats some weight,onto a very shiny surface

[tommyzooom]

If you are happy with weights etc, there are proprietary primers for tiling over glazed,impervious surfaces, like PCI primer 303,Benfer Starprim etc. I would be more confident with these than a slurry coat