Tiling over old walls...

taffyapple

I hope someone will be able to give me some advice on the following please.

I am in the process of taking the existing tiles off my bathroom wall in order to replace them with new ones. The house was built around 1930 and has the horrible "black dusty" plaster! Some of the walls were re-skimmed 3 years ago before being tiled. Now,whilst removing the old tiles, some of the plaster has come away in various places which is leaving the black dusty plaster exposed. Also there are 2 whole walls which were not previously re-skimmed (still have the black dusty plaster) but are still solid since removing the old tiles. My questions are..

1. Do I tile straight over the 2 "black dusty" plaster walls - if so shall I pva them first?
2. Shall I just "make good" the other walls which have chunks of plaster missing from them, then tile over them - if so do I need to pva over the plaster first?
3. If I wanted to, could I dot and dab plasterboard over the whole lot (so that the surface was smooth & flat) then tile straight over the plasterboard?

Any help or advice will be greatly appreciated!

EasilyAggravated

the answe is yes to all 3.
however with the plasterboard, ordinary plasterboard wouldnt do because of the moisture in the bathroom so you would need to spend more money on the plasterboard needed.
if you were to fill in the holes, obviously make sure none of the plaster around is loose. you dont want to be filling in the holes for larger ones to appear.
all you would then need do is stick your tiles to the wall. you wouldnt need to pva.
an alternative might be to have someone come in and skim the walls that havent been skimmed and repair the bits where plaster has come off. you wouldnt need to pva the walls first. just make sure you fill in the grout lines so no moisture can get behind the tiles

p4u1_2

Hi

Take a look at http://www.ultimatehandyman.co.uk/tiling/index.htm. There is an article at the bottom of the page which states why you should not use PVA as a primer before tiling.

I would use something like Carlite Browning to make good, not bothering with a finishing coat as your going to be tiling over the top. Some people swear by patching plaster but I have yet to try this. Use PVA to seal the wall before applying the plaster, I believe the instructions tell you to apply the plaster whilst the PVA is still tacky.

Good luck!

taffyapple

Many thanks to both of you for your helpful replies. I will let you know how it goes (or doesn't go!!!):)

cargo

Pva walls before plastering to seal surface and kill the dust.
Do not use browning as a surface to tile upon this deffo needs skimming,you may be confused with carlite bonding as this can be tiled upon.
Browning is very dusty and powdery when dry.
Personaly I would allways skim before tiling but I am well aware you can tile on bonding coat.

I am a Plasterer and not a Tiler but have seen many a tile fixed to browning and bonding and I know which ones fall off easiest.

nelly_2

cargo is correct and also to add, for an amature if you make c0ck ups with the bonding it scapes down easily, so you dont have to be a dab hand although it helps alot

taffyapple

Well...I've skimmed over the wall using multifinish plaster which looked fine at first, however after approx 20 mins the plaster started to crack and after leaving it overnight to dry out completely there are cracks almost everywhere!!! The plaster itself does not peel away from the wall and feels very secure. Is it safe to tile over?
Many thanks.

nelly_2

Its cracked because it dried too quick did you pva it first?

Pva not only makes the plaster stick to the wall it acts as a barrier stopping the wall suck the water out of the plaster like what has happened.

I always pva it then wait half an hour then do it again the 1st coat doesnt seal it very well the second one does though.

cargo

Eye Nelly is spot on,after the 20 mins you should have kept applying water to the wall and trowelling it up.
That said if it had started to crack you would would still have ended up with a crazed finish to the wall.

taffyapple

Many thanks to you both (Nelly & Cargo).
I did pva first - 2 coats but it cracked. I ended up hacking it all off the wall and starting again. Applied 5 coats of pva, re-skimmed and voila! no cracks:j
Many thanks to everyone who has helped