Which plaster type for bathroom?

[Brad77]

Hi, I'm decorating my bathroom.
I've been chipping off the old grout and loose plaster, not got back to brick anywhere yet, one wall has some concrete looking stuff with swirly patterns scratched in it, the others are plaster 2 walls are pretty good but one is quite soft (can be rubbed off with your hand)

I've been doing lots of reading up, I think I need to apply some PVA (about 1:4 or 1:5 with water) over the wall where the plaster can be rubbed off with your hand as dust/sand.
Afterwards I'll be doing a rough coat and finishing coat (or 2).
The bottom half of the walls will be tiled and the top painted.

What type of plaster do I need?
I'm thinking of going to B&Q and getting "Thistle Undercoat Plaster" and "Thistle Finishing Plaster" is this right for a bathroom or should I get some other type?
(in case you can't tell, I don't really know what I'm doing).

Thanks,
Brad.

 

[Richard C]

If the existing base coats are at all suspect, they will need to come off weather your plastering or tiling, neither will stick to an unsound base. If your tiling it’s best not to plaster as it affects maximum tile weight which can be a problem if your planning large format tiles & you will have to wait for the plaster to fully dry before tiling; this will be 10 days for a skim coat but up to 4 weeks for a base & skim & if you’ve not plastered before it’ll moist likely be terrible & not very flat which is the worst thing possible for tiling. If the existing base is sound with just holes where the tiles were & you’re going to re-tile, you can fill & level using cement based (Rapidset) powder adhesive which will allow you to tile the next day, otherwise use a quickset render. Where you’re re-plastering, it will obviously need re-skimming but I would advise you get someone in to do it or it’ll most likely end in tears if you’ve no plastering experience. Another alternative is to dot & dab Moisture resistant plasterboard in dry areas & fix waterproof tile backer board in wet areas (plasterboard is not suitable unless you tank it) & tile straight onto that. For ½ tiled areas, mark the line of your tiles & get the area plastered just below the line, wasting it in; MR PB must be primed before skimming.

I would advise you do a lot more research; read the Tiling Forum Sticky & Forum archive posts before you do any further work or buy any materials. As you admit you don’t really know what you’re doing it will prevent you making potentially disastrous & expensive mistakes; come back with specific questions when you need to.

Use only trade quality tiling materials not cheapo DIY shed stuff, it’s generally crap. PVA is the plasters friend but can be an inexperienced tiler’s worst enemy, don’t let it anywhere near surfaces you’re going to be tiling.

 

[Brad77]

Thanks for the quick reply Richard C.

I'm glad I asked, it looks like I would have got it all wrong.
So now the main wall along the side of the bath has had all the top coat of plaster removed but the base seems fine, so I'll skim the top half of the wall and tile straight onto the bottom half.
Two other walls look like the plaster is pretty good but the paint is flaking off in some places so that'll need scrapping off.
The other wall with the loose plaster, looks like I need to chip all of it off, luckily this is the wall with the door and end of the bath, so its not too big.

I'm not expecting anywhere near a pro finish on my plastering, I did half a wall in our kitchen when we moved in last year and it was fairly flat but cracked quite a lot, I've since read up more and i think i mixed the plaster too dry and definately put in on way too thick.
Our bathroom has been a mess since we moved in, previous owner had removed tiles. We've lived with it looking horrible for a year hoping to save up a little before decorating it, now we still have no money but decided that a bad job by me is better than it currently is, so we bought some cheap tiles and I started chipping off the old adhesive and loose plaster.

Thanks for the advice, instead of starting to plaster this weekend, I'll do a lot more reading up and remove the crap plaster from the wall.

 

[Richard C]

I'm glad I asked, it looks like I would have got it all wrong.

Many do & is why I like to get in early if I can. For me, it’s far better to advise the right way to do it than tell folks where they’ve gone wrong; sometimes personal pride gets in the way of admitting mistakes.

Advice on this forum is some of the best you will get & there are many regulars in various trades prepared to help.

So now the main wall along the side of the bath has had all the top coat of plaster removed but the base seems fine, so I'll skim the top half of the wall and tile straight onto the bottom half.

That’s fine but you may need to use a primer; Is it a Gypsum plaster base sand/cement? What type/size are the tiles?

Two other walls look like the plaster is pretty good but the paint is flaking off in some places so that'll need scrapping off.

You must remove all the flaking paint & seal/bond the surface as that’s all that will be holding the tiles or new plaster skim in place. For plaster use PVA or a PVA slurry if it’s bad but for tiles use an acrylic bonding primer or SBR slurry; do not use PVA.

The other wall with the loose plaster, looks like I need to chip all of it off, luckily this is the wall with the door and end of the bath, so its not too big.

If your taking it off back to brick, it will be far better to fix a 12.5mm waterproof tile backer board & tile onto that. If you need to skim a 1/2 tiled wall, make sure the backer board will accept plaster; despite what the manufacturer says, most will if you know what you’re doing.

I'm not expecting anywhere near a pro finish on my plastering, I did half a wall in our kitchen when we moved in last year and it was fairly flat but cracked quite a lot, I've since read up more and i think i mixed the plaster too dry and definitely put in on way too thick.

Mmm, the finished look is everything IMO. If your base/skim cracked up, you made some fundamental mistakes; probably the biggest mistake was not controlling the background suction enough but the mix could have been too dry, or taking far too long; applying it too thick usually works in your favour if you got the others right, although anything over 4mm will give you other problems if you don’t know how to handle it.

instead of starting to plaster this weekend, I'll do a lot more reading up and remove the crap plaster from the wall.

Wise move, take your time; a little more spent understanding what you’re about to do can make all the difference & come back if you need more advice.