Primer needed for tile adhesive on waterbased painted walls?

[Melissa4]

Hi guys,

Appreciate all the help on here. Another one please - have mosaic natural stone (travertine) pieces attached to plastic mats in 300 mm x300mm format tiles. Am going to repurpose them into a laundry splashback (adhere to wall, grout, seal etc). The wall is brick, with concrete render with multiple paint layers (latest layer is fresh, water based dulux). My question is whether dunlop mastic is the right tile adhesive and if so, is there a primer needed or should I just rough up the wall a little by sanding? Thanks so much!

https://www.kmart.com.au/product/4-pack-light-stone-decking-tiles-43101696/

[MitchellMc]

Hi @Melissa4,

Some types of paints can be tiled over; however, DUNLOP recommends that the best approach is to remove the paint from the substrate and apply the tile adhesive to the cleaned surface. Clean and properly prepared substrates always provide the optimal surface for the application of tile adhesives. The most reliable results will be obtained with DUNLOP TILE ALL adhesive. 

The other option would be to install a fresh cement sheet over the area instead of removing the paint.

Are you able to remove the plastic backing from the tiles? The product you linked is originally designed for use as decking tiles on the ground, and the plastic backing provides support in that context. However, for wall applications, most mosaic tiles are mounted on a mesh sheet, which allows tile adhesive to pass through and grip both the backing and the tile itself.

If you’re able to remove the plastic backing, then yes, wall tile adhesive would likely be suitable for adhering them directly to the wall.

However, if you leave the plastic backing in place, there’s a chance the adhesive won’t bond effectively. Plastic is typically smooth and non-porous, so there’s not much for the adhesive to grip. That makes success a bit uncertain. An alternative approach could involve physically fixing the tiles through the backing (e.g. using screws or anchors in combination with adhesive), but that’s a bit unorthodox for splashback applications and might affect the final appearance.

Given the uncertainties, it would be worth purchasing similar-looking mosaic tiles on a mesh backing, such as the Decor8 Tiles 300 x 300 x 10mm Beige Java Marble Tile Mosaic.

Please let me know if you have any questions.

Mitchell

[Melissa4]

Thanks Mitchell, I can remove the backing, was only keeping as hoping to reduce time in the tiling process, but should be fine. Not keen on stripping the paint (we're talking apartment built in the 70s so there is layer on layer) - are there no primer/adhesive combos suitable? I have seen ones ok for oil based painted surfaces, just not sure on water based. If not then sounds like I need to use cement sheet/villaboard as you suggest .

[EricL]

Hello @Melissa4 

I was in the same situation when I was renovating my kitchen. Remove my entire wall or put in a cement sheet. Since only part of my wall was going to be seen I decided to go with cement sheeting - Durasheet 2700 x 1200 x 4.5mm Fibre Cement Cladding. My best advice is to place a good amount of adhesive along with the fixing screws to prevent it from curving or lifting up. It is a much better surface to tile.

If you need further assistance, please let us know.

Eric