We're tiling a new ensuite shower area which was plastered 2 months ago, using ceramic tiles with waterproof adhesive. The adhesive sticks well to the tiles, but our problem is very poor adhesion to wall. After 2 days, can easily be lifted off by hand, with no adhesive left on the wall.
The plaster finish is pink and very smooth, but not dusty. The wall has not been sized.
Is it possible that wrong finish plaster has been used, or maybe an additve put in the plaster mix to cause the problem?
I've tried roughing up the surface with course glasspaper and cleaning off, but then still same poor adhesion.
[quote="plumbbob"]This is not a problem I have ever come across before. Is your wall adhesive correct or poor quality?
Try sealing a test area of wall first with a solution of PVA then see how the tile stick.[/quote]
The tech helpline at Bal stoke-on-Trent (adhesive mnfr) said specifically not to size the new plaster, including not to use PVA. But as an experiment, it will be interesting to try. Thanks for suggestion.
I too have never had a problem before, so I just wonder if a plaster manufacturer has changed the spec slightly to create this situation? If so, could effect whole industry? So meanwhile, we're trying to identify the plaster materials used.
Bal is a favorite brand of adhesives and grouts that we use on a regular basis, and have always found them to be excellent in all aspects.
Although non (as far as I know) of the adhesives recommend the use of PVA as a primer, and indeed I have heard comments about PVA peeling off, we often, if the wall is powdery, use a dilute solution to stabilise the wall prior to tiling. The instructions for PVA actually recommend it's use for such purposes.
Just a thought, has the wall been previously sealed with a silicone water repellent coat such as Thompsons Water Seal which may explain the poor adhesion?
I am not aware of any significant change in plaster composition but I am not a plasterer by trade, and we rarely tile on new plaster.
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