what's what?

[vosnack]

Can anyone explain or point to a proper thread as to how to deal with plastered finished walls, bonding thistle straightened walls etc. Because I just read about something called ettringite failure and it really worries me not to make any mistakes. As it happened few times i tiled over bonding with cement based adhesive, no primer. Also backsplash with ceramic tiles using tub adhesive over skimmed wall. Also if i tile over concrete screed do i always need ditra? I know for you guys these are basics, but i heard and read so many different opinions (sometimes ridiculous) that i don't know what's right. Thanks

[Dave]

Did you know you should not tile to bonding coat either... not your day..

Ettringite.. is a reaction between a cement based product and a gypsum based substrate.. as in tiling with cement based adhesive onto un-primed skimmed walls..

[Dave]

This might help as well..


P.V.A. Versus Primers

[doug boardley]

I suggest you read through the forum vosnack especially the "adhesive grout and substrate prep" section, there's a mine of info on here.

[vosnack]

i've read this 'PVA versus Primers' before posting this thread.that's how i foubd out about ettringite and tried to google more information but found not much. something about reaction which creates expansion and debonding.
I take it on board that it wasn't good to tile onto bonding surface (i was told once that it's ok on bonding but not ok on browning which now i know was total rubbish) although what is my option when the wall has bonding on it?Will proper primer do the job?
Fortunately about PVA I know from the begining. Of not using it obviously.
What about tube adhesive to do the backsplash? are these ok onto plaster skim?

[whitebeam]

The bonding needs a finish but depends what the tile weights are

[aph257]

Tub addy is normally on ok on skim, read the instructions though first. i only use tubbed on splashies.

[vosnack]

but i never had to tile a fully bonded wall. it was patch here and there maybe 2-3 tiles over the whole wall. So my question is why skim if plaster do react with cement based adhesive?
also if i need to tile uneven wall how do i make up these differences? with tile adhesive? it may take bags and bags sometimes.

[vosnack]

Tub addy is normally on ok on skim, read the instructions though first. i only use tubbed on splashies.

thanks. i meant the spalshbacks.

[whitebeam]

With the old type bonding very small patches maybe ok but still prime...

The new type bonding is a lot finer and feels like browning and bonding mixed together.

[davebates]

so can this be avoided by using the right primer ???

[whitebeam]

An acrylic primer, Mapei G, bal apd or sbr