Bathroom floor and wall tiling - new build

[whatdoiknow]

Ive been reading the posts here for a while as I am currently in the process of doing a self-build. its got to the stage now where I have to start tiling the upstairs bathroom and shower room. Although I have gone through a lot of past posts on the subject, I would appreciate some clarification.

Firstly, tiling on the floors, when the floor was put down, it was 22mm caberdeck P5 moisture resistant chipboard, I was adamant that I wouldnt have squeaky floors, so every single board has been screwed down onto the 9" X 3" floor joists with 15 screws per board, so there is no movement. Am I right in saying that I need to prime the floor with BAL APD? and that I do 2 coats, one at 90 degrees to the other? what length of time should I leave between coats and do I need to then tile the floor within a given period of time with a flexible adhesive?

Secondly, it appears I was rather stupid, in that I mist coated the walls, ive now been told by my plumber that I need to PVA the walls to seal them, as I could have tiled straight onto the new plaster, however, this would appear to contradict some of the posts that I may have misunderstood, do I PVA the walls and then prime them with BAL APD Primer, and then in respect of the shower cubicle, do I need to also use the tanking system on top of the primer, and do I put the tiles on before I put the shower enclosure on, the shower tray was put in before the plasterboard went up, so that the plasterboard sits on top of the shower tray ensuring that any water run off will not go behind the tray, my thoughts are that the shower cubicle was bought to fit the shower tray, theres already some space lost due to the plasterboard taking up 12mm, if I then put tiles on before the cubicle, there will be even less space to play with and my fear is that the enclosure wont fit.

Basically, can someone tell me the order of BAL?

Thanks in anticipation, this whole project has been one big learning curve, and you guys are the experts.

Cheers

[Fekin]

Not 100% sure about the floor, so I'll let someone more experianced answer that.

As for the walls, don't PVA them what-so-ever.

First of all, whats "mist coated" the walls ?

If it's plasterered walls and your using small standard ceramic tiles then you don't need to prime the plaster first because you'd be able to use tubbed adhesive, like Bal White star.
If you are using a larger heavier format tile, then you need better stick, so you'd use a cement based powder adhesive, but cement adhesive reacts against plaster, so that's why you prime the walls first with acrylic primer, then you can use cement based powder adhesive.

I would tile then fit the enclosure.

Personally I would have fitted new plasterboard, then fit shower tray, then tiled and sealed with silicone.

But if your going to struggle with the walls being filled out and the enclosure then not fitting, then tile around it.

[whatdoiknow]

HI thanks for the very quick reply, mist coating is where you mix up a 50/50 mixture of emulsion/water to apply a watered down paint mix to the new plaster, if you put straight paint onto plaster, it wont stay on for very long as the plaster is so porous.

[GazLC81]

Originally Posted by whatdoiknow

HI thanks for the very quick reply, mist coating is where you mix up a 50/50 mixture of emulsion/water to apply a watered down paint mix to the new plaster, if you put straight paint onto plaster, it wont stay on for very long as the plaster is so porous.

I would use BAL acrylic primer on the wall in that case.

Depending on the tanking system you buy it may come with a primer. BAL do a kit that comes with a primer you put on before the tanking system.

With regards to the floor prime the evening before and yes do it at 90 degree angle to each other.

I would think that given how well you have secured the floor you should be fine to tile straight on it using a flexible adhesive like Bal rapidset flexible and a flexible grout.

Like Fekin said don't use PVA it's not really a sealer.

HTH

Gaz

PS if you wait till this evening the real gurus will be here to answer your question

[Fekin]

Plaster does not need sealing with that distgusting 50-50 emulsion mix, if it is to be tiled on then.

Tile adhesive dosent like sticking to paint, so as I said before, new plaster only really has to be primed with acrylic primer if you are fixing the wall tiles with cement based adhesive onto plaster.
If using tubbed "ready mixed adhesive paste" like Bal white star onto plaster then you don't have to acrylic prime the plaster first, but you won't go wrong by priming it anyway.

Now on to the dreaded PVA.

I have taken this from a very useful post by dhceramics

When you treat a surface with PVA it partly soaks in and partly sits on the surface of the substrate much in the same way as wallpaper paste.

If PVA gets wet it becomes slightly live again, it doesn't completely return to it's liquid state but it becomes sticky.

When you spread tile adhesive onto the wall, the water in the adhesive makes the PVA live and stops the adhesive from penetrating the substrate and providing a mechanical grip. Basically your tiles, grout and adhesive are being held to the wall by a thin layer of PVA.

Most tile adhesive works by crystallising when it sets (some are slightly different such as epoxy based ones) but generally they all work the same way. Once the adhesive starts to set crystals from and expand into any imperfections in the substrate surface (at a microscopic level) to create a grip. PVA stops this process by creating a barrier between the substrate and the tile adhesive.

Ok so what's the difference between this and Ardex or BAL primer, well basically the tile manufacturers primers soak right in to the substrate and stop the sponge like "draw "effect but they don't coat the surface in any way, they are an impregnator as opposed to a barrier. They also stop a chemical reaction occurring between the cement based adhesive and a plaster substrate, a known problem know as "Ettringite failure"

I hope this clears up any misunderstandings.So only use PVA before tiling if the adhesive manufacturer specifies it in the instructions.

And I don't think many do.

----
Forgot to add, that emulsion 50/50 with water should only be used when decorating, ie painting the plaster and not tiling it.

[NickH]

I dont know how you can possibly seal around a shower enclosure that hasn't been fitted on top of the tiles. Everyone that i've ever fitted has had to go on top of the tiles. Measure the gap, allow for the thickness of tiles and see if its within the size range of your enclosure. If its not then you''l need to get a different enclosure.

[guy1976]

for the floor i would use a 2 part cement based adhesive (2 part is a bottle of liquid latex and a bag of powder )the latex replaces water in the mixing process.if your floor tiles are a light colour porcelain or a natural stone such as travetine or marble the adhesive will need to be white as ordinary grey adhesive can sometimes show through the tile face.for the walls i would prime walls with bal apd then use bal white star to fix.if the wall tiles are over the size of 300x300 then they are classed as large format and a cement based adhesive would be required
ps..as you have obviously spent a lot of money on building your house i would recomend letting a proper tiler do the job to get best possible finnish
as oposed to popular beleif quality tiling is NOT A D.I.Y JOB

[whatdoiknow]

many many thanks for all the replies, greatly appreciated and judging by the number of views, of great use to a lot of people, thanks guys.