Bathroom tiling over emulsion.

I want to tile the bathroom. It was originally painted with a vynal emulsion of some kind. I notice that it seems a little fragile in some places and comes of without too much sanding. What is the best approach, strip it all?
It is laid directly on the plaster and if as I fear it will have to be completely removed what is the best option?
Regards
HN
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H. Neary wrote:

rip off anything lose where you want to tile and tile.

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wrote:

I wouldnt even think about tiling onto anything thats at risk of coming off. Tiling lasts decades, the substrate has to last decades too.
NT
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Tabby wrote:

I'd have the loose stuff off and dowse the rest with SBR (or an equivalent tile primer) - that generally is pretty good at stabilising the surface and the penetration is better than PVA - and it's waterproof. BAL recommend that approach for new plaster - so it is compatible with tiling.
--
Tim Watts

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Thank you. My only problem is identifying what is "loose". Nothing is obviously lifting. I was planning on using PVA to seal the plaster incidentally but will certainly look into this SBR.
So far I have tried a combination of sanding and scraping using an Aldi palm sander. This removes the paint extreemely slowly. I have tried a chemical paint remover and oddly enough in small quantities it actually improves the paint / plaster bond to a remarkable degree. [I am loath to paint the entire wall with with it though as it probably has drawbacks as a bonding agent]. Used in standard bubble and scrape quantities, it is fine, but far too expensive for an entire room.
I didn't think chemical strippers worked on water based paints, and was a little dubious when I read the label [Some blue gel type stuff]. It works though but in exactly the same way as Nitromoors. i.e very effective, but dashed expensive if you want to keep the physical labour to a minimum.
I think I'll go for a bigger sander. Screwfix advertise an Erbaur or similar that takes 1/3 sheets, and the correct sanding sheets are available, unlike the Aldi device which seems to require some kind of sheet that is not generally available within this solar system.
I suppose this SBR doesn't penetrate through to the plaster/ paint interface? I have assumed anything laid on top of the paint [ Which if it is still on the wall is of an uncertain bond strength] would not penetrate and reinforce the overall bond. Obviously my blue gel paint remover must penetrate to the bond and indeed reinforce it, so would you think that this SBR might do the same?
Regards
HN
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wrote:

Running over with a steel (regular) wire brush will probably show you - also an advantage as it will score the paint and give the adhesive some extra mechanical keying.

I think the wire brush stands more chance - for tiling, a roughed up (even badly) surface is a good thing (TM).

SBR has very good penetrating powers if the surface is not waterproof. IIRC the BAL instructions were to dilute it 1:1 with water which makes it thinner. You need to saturate the surface in one go as it cures fairly quickly and then becomes waterproof limiting the penetration of any further applications.
The one thing it does not do is gap fill - so it won't help paint that is loose with a gap behind (even a tiny gap). But if the paint is stuck on, even if it - or the surface of the plaster underneath - is weak, it should make it most of the way through the skim coat of plaster and it will be noticebly more solid when dried. If any of the surface was fiable, it won't be afterwards. It is unlikely to help if the skim coat os loose though - you should tap the wall and sound it out and deal with any serious bits in the usual way.
One warning though - if spilt on any good finishes, eg floor tiles, bath, etc, wipe up immediately with plenty of water and a cloth - I have still got a layer of SBR on my stainless bowl I use for mixing various liquids and even wire wool won't shift it except in conjunction with white spirit.
It's difficult to guarantee success without seeing your wall, but if you do a test area, leave a day, then take a scraper and a wire brish to it it should be obvious if it has had the desired effect. But based on what you've said and the relative amount of work to try to strip the paint or knock the skim off and replaster, it would be the first thing I'd try.
Cheers
Tim
--
Tim Watts

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Thanks Tim,         Actually this paint seems fairly waterproof. I tried spraying a mist from a Hozelock bottle but it had little effect penetration wise.
I have tried a wire brush ( a cup attatchment for my drill), it seems to effect a slight improvement in some patches. If I turn the drill on I get grooves.
The surface of the paint is quite resillient, the only weak bit is the bond between plaster and paint.
My current plan thanks in part to this NG is a matrix of steel blades to groove the paint, followed by a good scrubbing with a Screwfix sander [if in stock].
Come to think of it I'll pick up a wire brush tomorrow, maybe a wire cup attachment isn't the best for scrubbing walls.
HN
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Tabby wrote:

If you can hold a tile with a couple of dots,. then overall adhesion is not that important
either the paint peels of. so peel it. Or it doesnt. So dont!

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On Sat, 02 Apr 2011 19:43:18 +0100, The Natural Philosopher

Thanks for the reply.
None of the paint shows ay visible sign of lifting, it was only when I sanded away some grout on a sink splashback that I realised there may be a problem.
Using a scraper there are areas where I can easily leave a few square centimeters clean of paint. Other parts of the walls can be difficult to clear. I do not know how much force is needed to remove the paint until it is actually off. There is always the thought that the combination of sanding and scraping that I am using to "test" the adhesion would maybe loosen the bond on a good paint job?
I did try sticking masking tape to the wall and peeling it away, over half a meter a couple of 2cm^2 patches came away. Masking tape is approximately 5cm width.
I was thinking of a bigger sander. I did give a chemical stripper a try but unless used in extreemely liberal amounts it seemed to increase the bonding to the plaster as the paint was no longer as brittle.
As you are probably aware my practical experience of this type of work is virtually zero, so I would welcome any suggestion that would help me avoid spending a week or so trying to remove the paint using my current technique.
Regards
HN
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On 02/04/2011 21:09, H. Neary wrote:

Try a steam cleaner or wallpaper stripper to soften it then use a scraper. It worked for me with some Dulux kitchen emulsion but YMMV depending on the type of paint you have
--
Mike Clarke

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Mike Clarke wrote:

In the end you are simply looking for the least effort way to remove or nullify that which makes tiles fall off.
On reflection,. a damned good scrape of one sort or another would seem to be optimal.
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On 02/04/2011 18:45, H. Neary wrote:

I found, by accident, that brushed-on meths softens emulsion to allow it to be scraped. I've used it to remove old paint for tiling. Not recently so maybe there are chemical changes in emulsion, but perhaps worth an experiment.
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On Sun, 03 Apr 2011 13:12:31 +0100, Peter Scott

Always one to avoid the unpleasantness of physical labour, I have given it a try. There was no discernable effect on the paint layer.
Thank you for the information though, it may be of value in a future project.
HN
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On Sat, 02 Apr 2011 18:45:23 +0100, H. Neary wrote:

I think I'd screw 1/4" cement board onto everything and then tile onto that - it's more expensive to do it that way, but it'll give you a good secure base that'll last even if moisture does ever manage to penetrate between the tiles.

Plasterboard (aka drywall this side of the Pond) is really cheap over here - I'm not sure about in the UK, though. Tearing down what was there and putting up new boards would certainly be a possibility here, anyway.
cheers
Jules
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On 02/04/2011 18:45, H. Neary wrote:

Now listen, I'm gonna tell you a story...
Our last house was bought when it was about 3 years old. One day we heard a loud bang, and a noise like plates breaking. Couldn't track it down. Until the kid's bathtime.
It turned out that the bathroom fitters had taken a shortcut. Worked out where the edge of the tiles was going to be, painted the walls, then tiled over it. The emulsion went over maybe the last foot of the wall under the tiles. (this was of course builder's thin magnolia)
The emulsion made a weak layer in the tiles, and the whole top row had come away. One landed on its corner, and punctured the bath. We called the builders, and they replaced the bath (not without some cursing, as it turned out the taps on the new one were in a slightly different place) and replaced the tiles.
Six months later...
... I noticed that the tiles were coming away. So I carefully (_very_ carefully!) removed the top two rows of tiles, cursed the paint underneath, scored the plaster heavily and refitted the tiles.
AFAIK it's been fine since. We were only there another 5 years or so, and it didn't move.
Andy
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