Hi.

I have mosaics in my shower cubical which have failed due to lack of tanking. I'm about to rip out the shower and mosaics, tank the area properly and replace with a showerbath and new tiles.

Once I have scrapped off the old mosaics and adhese from the shower area, I'm hoping that the existing Bonding and Skimcoat will be relativly flash and intact, but I have some basic plastering skills so I can always reskim/fill holes if need be…… but I have the following questions/worries:

1) Because the showerbath requires a larger area that the existing Shower cubical, the new area to tanked/tiled will be 50% where the old mosaics were, and 50% painted wall (blockwork/bonding/skim). I'm concered that the weight of the tiles might pull the existing plaster away from the wall. Instead of prepping the wall after removing the tiles, should I just put up new plasterboard on-top of the Bonding/skimcoat? Would this have better weight-holding properties?

2) If putting up plasterboard instead of using the bonded/skimmed wall would be better, what type of plasterboard would be most suitable, and how should it be fixed - Dot and dab, or screwed ?

3) Will I need to prep either the existing wall (or new plasterboard if that is advised) with some kind of adhesive/bonding agent before tanking ?

4) Do I tile straight onto the Tanking, or does that need prepping with an adhese agent too ?


Thanks very much for any words of guidance.

hello
What kind of tiles will you be using?
/bonding/skim holds 20 kg per sq meter
If you will be using porcelain then you should strip to bear block and dot and dab green plasterboard leave 5mm gap between floor and wall + fix some screws too, it will be mechanically fixed for extra strength, tank the shower area and 50cm past the shower area, all plasterboard joins should be taped with fibreoptic mesh

Hello and welcome..

The weight issue only comes in ,if the tiles are too heavy for the background substrate.

If the mosaics come off and not a massive amount of damage then you can just infill and tank over..but it needs to be flat to get a good finish.

The area that you now wish to include int he new showering/tiling area that is painted, needs the paint removing,this can b e done by sanding it off.

Tanking does not require any additional preparation once applied but you must follow the directions on the tanking kit to prep before tanking.

And my advise is too use a flexible cement based adhesive on the tanking as this performs better for adhesion and any issues with water.

Hi, thanks for advice.

The tiles weight 16.8kg per M, so I'll tile straight onto the plaster skim then. However, two things I am still worried about…..

1 The walls were originally PVA'd before they were painted and tiled, but I have since read that PVA should not be used. Once I have sanded off the existing paint and scrapped off the old mosaics, will the wall still be okay to tank/tile or would the PVA have soaked into the skim and weakened it?

2) The walls will be damp due to lack of tanking in shower area. Once the Mosaics are scrapped off, how long should I leave the walls to dry out before I can apply my BAL tanking kit and start tiling ?


I don't want a 500 x 300 tile falling off when someone is laying in the bath, so am just a bit concerned.

Many thanks.

Petey, have you factored in the weight of adhesive and grout, approximately 4kg per m2? personally I'd be taking off the bonding and skim, and plasterboard the walls. There won't be that much more work involved and it'll give you peace of mind

i agree with Doug!!,no worries then about the dreaded PVA

okay guys, that makes sense and then I won't have to worry!!!

Once I have removed all the existing plaster (which I'm guessing the easiest was is with an SDS chistle?) how should new plasterboard be fixed - battons or dot and dab?

Also, I have a tanking kit, so should I use Aquapanel or just stick to normal plasterboard ?



Many thanks
petey.

i would personally go for cement board, and combe the substrate if suitable and go for full bed fixing of the cement board
but you can still use pl/board, Aquapanel its up tp you and the cost pete

Awesome, thanks. I will order some Hardibacker from ToppsTiles.

I suppose the 12mm is better than 6mm ? Even though I have very little space as the bath JUST fits in, I guess 12mm will have less likelyhood of moving ?

I don't understand what you mean in regards to fitting it? Instead of battens, are you suggesting applying some kind of adhesive to the wall and sticking it up, almost like a giant tile ? What do I use for that, and is it easier to get them flush rather than battons? Will they still be as stong using adhesive rather than battens?


Many thanks guys, sorry for being a dummy!

hardiebacker shouldn't be stuck onto a wall with just adhesive Petey, if you have room to batten the walls out, that would be the best option

Hi again folks.

Just been reading up and seems that a lot of you pro-tilers like to tile onto Render??

If I'm removing the plaster to make space for battens/hardibacker, why don't I use the money I'd spend on Hardibacker and just get a plasterer to Render the walls ?

I'm guessing that a layer of render will take less space than 25mm battens and 12mm Hardibacker ?


Any opinion on this course of action ?

Originally Posted by Petey

Hi again folks.

Just been reading up and seems that a lot of you pro-tilers like to tile onto Render??

If I'm removing the plaster to make space for battens/hardback, why don't I use the money I'd spend on Hardback and just get a plasterer to Render the walls ?

I'm guessing that a layer of render will take less space than MM battens and MM Hardback ?


Any opinion on this course of action ?

yes but you must leave it about three weeks to cure,if you use sand and cement

Hmm - 3 weeks?!!?!?

Okay, so basically the choices are :

Hardibacker on Battens, which would be ready to tile on instantly, but I'd lose approx 37mm in space.

SC Render - which would be approx 15mm deep, but I'd have to wait 3 weeks to cure.


I've just read a post where someone got a SC Render done, but the workmen didn't do it properly as, after six weeks, it was dusty and loose in patches. Is this a common occurance? Is rendering difficult ? It's hard enough just to get a plasterer it seems ?

I think for speed and ease of construction in your scenario petey, I'd go down the dot and dab 12.5mm plasterboard route, you can always mechanically fix your plasterboard too

You can mechanically fix the hardie too. Drill and plug it to the wall. Dot and dab is the quickest and easiest.

Hi foks, thanks for all your advice.

I have decided to render the walls, and will be doing it myself. I have some experience with bonding/skim plastering, so I should be okay with the actual skill involved, but I can't find a definite answer on the web as to the render mix, which additives to add, and if it should be one or two coats done with slightly different mixes? Could anyone tell me what wis the correct way of doing it ?

Does 5:1 Sand Cement sound right?

Do I do it in two layers of approx 7mm or just one layer of 15mm ?

Do I add plasterciser rather than waterproofer, or neither ?



Many thanks everyone.
Petey.