Once the cavity wall insulation is removed from the walls we are looking to replace the render on the house for a uniform finish. I was disconcerted by information I discovered regarding thermal requirements imposed during rendering. https://www.planningportal.co.uk/info/200130/common_projects/18/external_walls/2 Where 25 per cent or more of an external wall is re-rendered, re-clad, re-plastered or re-lined internally or where 25 per cent or more of the external leaf of a wall is rebuilt, the regulations would normally apply and the thermal insulation would normally have to be improved. Does this really mean that I would have to consider installing more insulation before I am allowed to render the house? The planning portal says 'have to be improved' - which is what we are doing by removing the wet insulation.

This does not look good. I'm not a materials expert but it looks like this is a poor match for the rough cast render. My basic understanding is that if you stick two materials together of very different composition then they expand and contract at different rates. Add to this different moisture and vapour permeability and there will inevitably be problems. It does look like the rendering on our house started to deteriorate after the CWI was installed. To the layman, it seems quite obvious that drilling random holes into your house is a terrible idea.