How to install tile backsplash on top of old adhesive?

johnnym

Project is tiling a new splash back in the kitchen. Have removed the old tiles and scraped off old adhesive as much as possible using a rotary hammer drill.

Glue is incredibly strong more so than the render it is attached to. Next steps is to prepare the surface for the new tiles.

Does this require primer to be painted on then some sort of mud or joining compound to get the surface level again? Not sure on the exact products to use. part of the project is on new cement board, does that need to be primed before applying tile adhesive? Would appreciate a little guidance.

JacobZ

Hi @johnnym,

Welcome to the Bunnings Workshop community, it is wonderful to have you with us.

You've done a great job so far, and I know from experience how tricky it can be removing old tile adhesive. As the tile adhesive is extremely well bonded to the substrate, you don't need to get every last bit of tile adhesive off, but you do need a solid, flat surface to work with. Tile adhesives work best when they can suction to a flat surface, so with the uneven notched nature of the surface at present, the adhesive will not suction to the surface as well as it should.

To get a flat surface, you’ve really got two options. You can build the wall back up with render or continue removing as much of the existing adhesive as possible. Removing it tends to be more labour intensive, but it is usually the simpler and more cost-effective approach than rendering.

Rendering over the top also adds weight and a bit more complexity, as you are creating multiple layers for your tiles to bond to, which can introduce additional potential failure points if not done correctly.

It doesn't need to be perfectly flat, but you would be best to remove as much of the tile adhesive as possible. At this point, I would suggest using a wire wheel attachment for either an angle grinder or drill to remove as much of the adhesive as possible. In doing this, it is essential that you wear a mask, eye protection, hearing protection and protective clothing to keep yourself safe.

If there are any deep gouges or major height differences, then you can fill them with a render patching compound like this https://www.bunnings.com.au/dunlop-4l-premix-render-joint-and-patch_p0760324 ensuring you follow the instructions on the packaging closely.

Once you have removed the bulk of the adhesive, have rendered any gouges and have a relatively flat, stable surface, you would prime the wall with a product such as https://www.bunnings.com.au/davco-1l-ultraprime-surface-primer_p6658116 . A primer will help the adhesive grip better, especially if the surface is a bit dusty. It also stops the wall from soaking things in unevenly which makes the whole job a bit more reliable.

After this, you can get stuck into your tiling. https://www.bunnings.com.au/diy-advice/diy-skills/tiling/how-to-tile-a-splashback is a great resource you can use to guide you with the tiling.

Let me know what you think and if you have further questions, please don't hesitate to ask.

Jacob