Tiling over Cornerstone Insulating Render

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I’m interested in your Cornerstone insulating render, I have a query. My application is a 1930s red brick house, I wish to use it in the bathroom to insulate internally. I have the room stripped back to the brick. It is lime mortar and uninsulated cavity, I do not plan to insulate the cavity. I need to tile the bathroom, some walls full height (shower enclosure) and others half height.

I’m trying not to use modern materials but I’ve been told that if I tile onto the Cornerstone render that I may encounter issues with the adhesive failing to adhere or perhaps failing in the future due to moisture penetration.

Do you have any thoughts?

Is it a workable option to use Cornerstone render, maybe 40/50mm then apply shower tanking paste over it and then tile onto the tanking paste? I know this will mean the render becomes non-breathable into the room, but the cavity will not be insulated and moisture could breathe into the cavity?

The bathroom is on the first floor so no damp issues, unless I create them!

Thanks in advance.

andy_s_kerr Unselected an answer May 6, 2022

Thanks for getting in touch.

We wouldn’t advise using tiles over tanking for 2 main reasons –

  1. Vapour permeability – any moisture from the render or wall will be pulled through the render and this could build up behind the slurry/tile and cause failure (we appreciate this isn’t as relevant for this project as its cavity).
  2. Weight – the Insulating Render is a lightweight material and is not designed to take the weight of things such as tiles, there is a chance the weight of the tiles causes the render to de-bond from the wall.

If you would like to discuss in further detail please don’t hesitate to give us a call on 01208 79779.

andy_s_kerr Unselected an answer May 6, 2022
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