Priming a plastered brick wall

[Sabiya]

Hi all, hoping for some advice. We purchased some splitface slate tiles from tilegiant and had them put on a brick wall that had been plastered with bonding and multifinish. 6 months on they have all come off, the adhesive is on the back of the tile but not the wall, it hasnt taken to the wall at all. He tiler said he used pva which i have since learnt is wrong. We are having it redone. Tile giant have advised to use primer g on the wall. My questions are do we need to score the plastered wall before applying primer g? Is primer g ok or bal apd? And what is the best adhesive, i was looking at a c2t adhesive. Thanks all! We cant afford a new tiler and the one has said he will redo for free.

 

[Grazza]

Did you not ever get a response for this?

Im in the same boat except Im considering tiling on the same as yours.
I got some Primer G from Tile Giant and am testing it with heavy scoring. with 40Grit and cant see why it would fail.

Howver, everything says not to do it if its over 20kg/m,.

So was the PVA the weak point where it separated? Not surprised.

 

[Grazza]

British Gypsum pretty much say the bonding agent is why its limited, from my interpretation.

See page 3:

https://www.british-gypsum.com/documents/product-data-sheet-pds/british-gypsum-pds-thistle-multifinish.pdf

 

[Sabiyanasima]

I didnt get a reply, tiler hadnt used pva at all, he’d tiled direct onto the plaster and it had soaked up all the moisture from adhesive which caused separation. I put a wet finger on the plaster and it soaked it up. I think he just forgot to pva as he did all the other house fine. Anyway he came back, we used bal apd to prime the walls and the bal adhesive. We didnt score. Seems to be ok so far. Been three months.

Did you not ever get a response for this?

Im in the same boat except Im considering tiling on the same as yours.
I got some Primer G from Tile Giant and am testing it with heavy scoring. with 40Grit and cant see why it would fail.

Howver, everything says not to do it if its over 20kg/m,.

So was the PVA the weak point where it separated? Not surprised.

 

[Sabiya]

British Gypsum pretty much say the bonding agent is why its limited, from my interpretation.

See page 3:

https://www.british-gypsum.com/documents/product-data-sheet-pds/british-gypsum-pds-thistle-multifinish.pdf

Hi sorry for late reply, he hadnt used pva, he probably thought he had but hadnt. U could tell as plaster was bone dry, powdery and sucked up a wet finger mark where the tiles came off. He redid it using bal apd primer and so far so good. Been a few months seems ok.

 

[Sabiya]

Also he didnt do any scoring either time

 

[Grazza]

I thinks its a bit of a minefield - loads of people have an opinion and like many things they are probably all valid for the particular. And then some poepl maybe got lucky.
Im gonna score mine.

I did my ensuite 2 years ago - with BAL sbr on smooth unscratched plaster with porcelain tiles and they are very much stuck on!

This time however Im gonna foam-board one of the walls as the plaster sounds a bit hollow near the ceiling. If that tile were to fall ....