Tile failure

[Spud]

Today I went to a job my team and I completed. 3 years ago, 4 bathrooms , 90 m Jura limestone floor,
the home owners main family bathroom was tiled in 30x 30 slate there was a section of tiles about 3 m2 on the external wall which had failed ,I stripped the tiles off the tiles pulled cleanLy away from the wall leaving what looked like an unprimed plastered wall, it really stumped me as all my work is primed with Tilemaster prime plus
We re primed the wall with more SBR and retiled it with new tiles
does anyone have any idea / theories on why after 3 years the wall failed?
The backs of the tiles seems to have a weak dust dusty layer of plaster on them solid bed of adhesive about 6-8mm thick no cracking on the external wall at all

 

[White Room]

Is the wall a cavity or solid wall...

 

[Spud]

Not sure mark it's a 1912 built house

 

[White Room]

That would be a good chance of a solid wall with lime mortar joints, had the wall been re-plastered or did it have remains of lime plaster on the wall.

 

[Spud]

It had been replastered the wall is really solid and the plaster is in good condition

 

[Colour Republic]

Any idea of the timescale between the wall getting skimmed and t then being tiled?

 

[Spud]

Any idea of the timescale between the wall getting skimmed and t then being tiled?

I can't remember to be honest Rob, one of my guys tiled the bathroom while I did the the limestone floor , it was dry though not damp

 

[White Room]

Sometimes over wetting the plaster (when plastering) and bringing to much fat to the surface can cause a powdery surface.

 

[Chalker]

Could it be the same problem that decorators have on over polished finish?

 

[Colour Republic]

I can't remember to be honest Rob, one of my guys tiled the bathroom while I did the the limestone floor , it was dry though not damp

Sorry Gary wasn't implying the plaster was still wet, I wouldn't think you would fall foul of that one. In fact the opposite and the plaster was applied months before and was maybe too dry.

It seems from your description that the failure has happened at the primer suggesting that the primer didn't penetrate far enough in to the surface and just sat on the top.

This can happen for a number of reasons, with any coating, one of which is that the plaster is so dry that it draws the moisture out too quick (one of the reasons for applying a primer in the first place!) I suppose you just get a feeling of how dry it is as you apply a coating and then it's best to stop and water the primer down so more, a 6-1 ratio instead of 3-1 let’s say, then apply a further coat of primer at the recommended ratio after the first one is dry, or nearly dry. If you've ever seen paint flake off a wall, you often see a dusty finish on the back of the paint if the first primer coat dried out too quickly and didn't do its job..

Another is as Whitebeam say, too much fat has been brought to the surface and your primer has stuck to the fat and not the plaster. Although you can normally tell just by looking at the wall when that’s happened as it's much lighter in colour than it should be and most of the time very patchy. Again you can see dust on the back in this case too.

Also as Chalker says, if a walls been over polished it can close up the surface to such an extent that it rejects any coating and it just sits on the surface not bonding at all. Although in this case you don't normally see a dusty surface on the back of the coating and the wall can visibly look shinny still.

It's worth noting that British Gypsum state that when plastering walls to receive tiles that it's better not to polish the walls at all and to leave the surface rougher than you would do if you were painting it. Although we all know that isn't always up to the tiler in how the wall plastered.

Of course there could be 10 other reason why it's failed but from what you describe I think the problem has to be either the primer or the plaster

 

[Dougs Third Go]

I rang Tilemaster up a couple of years ago (first time I used Tilemaster) as I was concerned about the dilution ratios. I felt that a neat undiluted coat as stated on the bottle wouldn't penetrate the plaster and just sit on the surface, I was told that 2 coats of 1:3 ratio would suffice, which is what I've always done since. Did your mate dilute the primer Gary?

 

[Spud]

I think Rob and Mark has described it really well Doug the plaster was very patchy in colour we always dilute 3:1thanks for the help on this I retiled it yesterday but was scratching my head as to what may have caused it to fail

 

[Ajax123]

One of the things that can happen with acrylic primers when in alkaline conditions is that they go through a chemical process which I know as alkali burn. This happens in the presence of small amounts of moisture. Perhaps warm damp bathroom meeting cold solid wall has caused condensation to form at the interface between the tiles and the wall...