I have an existing bathroom and am looking to build a hob around the bath. To do that I'm looking at building from hebel over the existing tiles. What is the best adhesive to use?
Welcome to the Bunnings Workshop community @Geoffh. It's great to have you join us and many thanks for your question.
I'll have to defer my answer until I can speak with CSR on Monday to get the correct information for you. After reading through many technical installation spec sheets on AAC/Hebel blocks I can't find a definitive answer to your question.
Hebel blocks are bedded and glued together with what is essentially a thin bed cement product. My concern with just advising you to use Hebel adhesive to attach the blocks to pre-existing tiles is that cement products have a notoriously hard time adhering to glazed or gloss surfaces. I would imagine laying a thicker bedding layer and placing the blocks on top would be perfectly fine, however, there would be little to no adhesion going on there. That might not be an issue, but I would like to double-check with CSR's technical assistants before giving an answer.
Let me mention @Brad to see if he has come across bedding blocks onto pre-existing tiles before.
I'll update this discussion as soon as I have some relevant information for you.
I've now been able to have some discussions with both CSR and Dunlop about your situation and how you can adhere the AAC Hebel blocks to tiles. Both companies have suggested you'll have the best results from removing the tiles. Alternatively, there will be some prep work prior to glueing the blocks down.
You'll need to remove any gloss or glazed surface on the tiles. This can be achieved with an angle grinder and a grinding disk. Once the gloss layer has been removed you can then add a 1mm thick skim coat of Dunlop 2kg Tile-all Tile Adhesive Kit over the area and wait 24 hours for it to cure. After the Tile-all has cured you can use Dunlop 20kg Dry Mix AAC Concrete Block Adhesive to start adhering your blocks to the surface and building your hob.
Please let me know if need further advice or have any questions.