Can you waterproof when tiling over existing tiles?

[suetang]

We have shower area is leaking. We are going to retile the whole area. However,  the shower base tiles are very hard to be removed. So we are thinking of tiling on top of them.  Can it bedone? Can we apply waterproof over these tiles before we put on new tiles? Thanks

[PlumbMaster-Zee]

Hi suetang,

Yes, you can waterproof when tiling over existing tiles, but it requires proper preparation to ensure a durable and effective result.

Here are the steps you should follow:

1. Clean the Existing Tiles: Thoroughly clean the existing tiles to remove any soap scum, mold, or grime. Use a strong tile cleaner or a mixture of water and vinegar.

2. Check for Soundness: Ensure the existing tiles are sound and securely bonded to the substrate. If any tiles are loose or damaged, they need to be repaired or replaced.

3. Roughen the Surface: Use a sander or grinder to roughen the surface of the existing tiles. This will help the new waterproofing membrane and adhesive bond properly.

4. Apply a Primer: Depending on the type of waterproofing membrane you use, you may need to apply a primer to the existing tiles. Follow the manufacturer's instructions.

5. Waterproofing Membrane: Apply a waterproofing membrane over the existing tiles. Make sure to cover all joints and gaps. There are different types of membranes, such as liquid-applied membranes or sheet membranes. Choose one that is compatible with your tiles and adhesive.

6. Tile Adhesive: Use a high-quality tile adhesive suitable for use over waterproof membranes. Apply the adhesive with a notched trowel to ensure a strong bond.

7. Install New Tiles: Install the new tiles over the adhesive, ensuring they are properly aligned and spaced.

8. Grout and Seal: Once the adhesive has set, grout the new tiles and seal the grout lines to prevent water infiltration.

By following these steps, you can effectively waterproof and retile your shower area. If you're unsure or need more specific advice, consider consulting with a professional tiler.

Good luck with your project!

Zee

[MitchellMc]

Welcome to the Bunnings Workshop community @suetang. It's brilliant to have you join us, and many thanks for your question about tiling over tiling.

To follow up on @PlumbMaster-Zee's advice, you can use Crommelin 1L Tile On Tile Primer over your existing tiles. Before applying it, ensure no gaps exist between the existing floor tiles and the walls. If there are, they can be filled with Crommelin 300ml Hybrid MS Polyurethane Sealant. The membrane will go over the tiles and primer then up the walls in one continuous layer. 

Once the membrane is established, you can follow this guide: How to tile a shower base and How to tile a bathroom wall.

Before you start work, ensure that you don't require a qualified waterproofer to conduct this work.

 
Please let me know if you have any questions.

Mitchell
 

[suetang]

Thank you so much. Mitchell

This is very helpful.