I have used unibond tile adhesive before with no problems, I know it doesn’t get much love on here but I've never had any problems.
The powder stuff is better than the tub mix but conditions have to be spot on. I wouldn’t push my luck with either & a search on any of the tiling forums will throw up plenty of folks who subsequently wished they hadn’t & posting for advice from the pro’s.
So ultimately I probably don't need to prime if I use the pre-mixed adhesive,
Not always & it depends on the adhesive manufacturer but sometimes it is necessary & each case is different. Yes when using powder adhesive over gypsum & you need a bonding primer if the plaster has been over polished.
although I need to decide if I want to go ahead with the pre-mixed on the basis my tiles are boderline too heavy.
The size limit on using pre-mix is not primarily about the tile weight although this is a factor. Pre-mix cures by evaporation & the only way moisture can evaporate is through the grout lines, with large format tiles, the adhesive in the centre of the tile won’t set & this is what causes the problem. Powder adhesive is chemical cure so the problem doesn’t exist but it’s no more difficult to use that tub mix. The weight limit I gave is for plaster skim so if the tiles exceed this you should either pick smaller tiles or change the tile base for one more suitable.
My mum had tiling done in her new shower about a year ago, early on you could see the tiles were changing colour after the shower was being used and now the tiles are patchy under the surface. What would make this happen? it all seems to happen below the border mosaics, has the builder not used waterproof grout or something?
Water was obviously getting behind the tiles, does it still happen? How quickly after tiling did she use the shower, new tiles in a wet area should be left for 2 weeks before using! It could be water getting through cracks in the grout or permeating the grout itself; most adhesive & grout is waterproof but, apart from expensive epoxy products, it’s only “waterproof” in the sense it won’t (shouldn’t) disintegrate when wet, it’s not impervious to water. This is why it’s important the tile base is truly waterproof if regular wetting of the tiles is going to occur. If she has a concealed mixer valve or pipe work, it could a leak from either of those, difficult to say without seeing it or knowing what materials were used. This is why quality tiling materials are so important if you want it to last; you generally only get what you pay for with this stuff.
I have offered to pull the offending tiles out and re-do those arease for her but not sure what caused it in the first place.
If your going to do that (& I’ve done plenty), be prepared for the worst with what you may find behind. If it’s standard plasterboard behind & it wasn’t tanked, it’s probably going to be in one hell of a mess & need replacing. If you leave “as is”, it will most likely fail eventually but at least be usable in the meantime; however, depending on the wall construction, this may cause even more damage.
Sorry but you didn’t answer my question about how you stripped the paint off or if the walls are plaster board stud or plaster over block work.
