Help - no bathroom, preparation for tiling

jennynoo

We are currently trying to renovate our bathroom so at the weekend took out all fixtures apart from the toilet and removed the old tiles however when trying to take off the adhesive most of the skim plaster also came off. We are in a victorian property with lath and plaster walls, most of the wall is back to the rough reddish plaster with a few holes and cracks then parts still have a smooth surface with some paint on.

A builder told me I can just cover wall with PVA then tile straight onto wall as it is but wont I end up with wonky tiles?

Please help newbie DIYer.

tanith

I think your builder probably meant for you to fill the holes in first then cover with PVA .... we did this 2yrs ago and thankfully my son-in-law did an ok job of filling in the holes and making a fairly flat surface to tile over, he did also have to even out some of the wall by putting more adhesive under some of the tiles but it came out almost perfect...
Not an easy job for a newbie DIYER though..... maybe you could just get in a plasterer to fill and skim the walls before you tile....

jennynoo

Dear Tanith

Thanks for your quick reply, please can you tell me what your son-in-law used to fill in the holes and also how long we have to wait for the filler and/or PVA to dry before we can tile - want to know how much longer I'm going to have to manage without a shower!

ormus

doing smallish holes is easy. anything larger than a float/trowel size is harder.
but you dont need to be too precise if youre tiling over the top.
24/48 hrs should be ok to tile over.

if plastering frightens you then why not consider using aquapanel instead?

tile_guru

NEVER TILE TO BONDING PLASTER................

NEVER TILE TO PVA.............

NEVER TILE TO AN UNEVEN SURFACE...........

ok shouting over....

Get yourself some plasterboard and plaster board adhesive. Dot and dab the plaster board onto the walls. Tile onto the plasterboard.

This will be the safest and most cost effective way.

Guru

BobProperty

andrew-b wrote: »

I'd be interested to hear why you should not tile to bonding plaster? I have a scientific background so like to understand reasons why.
I spent a fair while researching this at the time and could not find anywhere a reason not to.

Andy

Hmm, now you've asked....

Maybe urban myth combined with use of PVA priming and weightbearing capabilities?
I'll be watching for the answer too.

jennynoo

Thanks for all the information. This seems to be a confusing issue with many different opinions. I bought the PVA last night and it says we can use it for tiling but it looks as though I will have to take it back although I have heard some people say that I still need to use the PVA for the areas where there is still finishing plaster with paint on???

I bought the bonding plaster to fill in a few holes and they are looking good now. Bit disappointed if I can't now tile onto the bonding plaster. We didn't want to put plaster board up as the bathroom is tiny and those millimeters are important leg room for the toilet!

Do you think I should have a go a putting finishing plater on? Surely it wont matter too much if we are going to tile over it. No rush at the moment as the builder doing my kitchen has removed my kitchen sink and the electric shower (on the wall I want to tile) is the only source of water in the flat!

tile_guru

Bonding plaster...

The rate that the moisture is drawn from the adhesive on bonding plaster is rapidly increased compared to a skim or finish coat plaster. When the rate of the disipation of water increases it increases the shrinkage of the adhesive. This can cause cracking in the adhesive and worst case adhesive de bonding from the tile causing the grout to be the only thing holding the tile to the susbstrate..

PVA is water based and will be broken down with water.

Plaster should be primed, which is an advanced polymer. Quite simply the water content takes the advanced polymer into the plaster and evaporates leaving the polymer behind which has by now coated the particle of plaster and protecting it from the cement content in cement based adhesives....

these are not always needed if a dispersion (ready mixed) adheive is being used..

Hope this helps Guru

jennynoo

Thanks a lot Andy! So I will get rid of the PVA and find something to sand down the painted areas. Then unless someone gives me a reason not to tile onto bonding plaster I will do a skim with bonding plaster then tile with waterproof adhesive and separate grout. I reckon it will be fun! (keeping my spirits up even though I'm dirty and tired

BobProperty

tile_guru wrote: »

Bonding plaster...

The rate that the moisture is drawn from the adhesive on bonding plaster is rapidly increased compared to a skim or finish coat plaster. When the rate of the disipation of water increases it increases the shrinkage of the adhesive. This can cause cracking in the adhesive and worst case adhesive de bonding from the tile causing the grout to be the only thing holding the tile to the susbstrate..

I'm surprised that one, the difference is so great and two, that no adhesive manufacturer has an adhesive or primer that would not overcome such a problem.

jennynoo

Thank Tile Guru for the explanation. Do you think if I go buy the tile adhesive it will tell me which primer to use?

Why can't it be simple - the plumbing was easier than this!