How to retrofit an old solid walled building with breathable internal wall insulation + lime plaster

Corkboard Internal Wall Insulation + Lime Plaster Retrofit Upgrade

Hi everyone,

After working on a partial retro fit to an old stone building in a Sheffield conservation area thought I’d share a bit about how the internal wall insulation and lime plastering came together.

So, I completed some specialist training a few years ago, the SPAB Old House Eco Course, and learnt a lot about the key issues with old solid walled buildings, how they behave differently and how they need to breathe to deal with moisture.

We initially looked at a thicker insulation build up to get a decent thermal performance upgrade but this would have been a heavily insulated timber frame wall. This was too thick and too much floor space would have been lost. We therefore decided to go for a thinner build up, with slightly reduced thermal performance.

The final build up used was 10mm thick lime plaster levelling coat + 10mm thick Isovit mortar + 50mm thick expanded cork board + 9mm thick lime plaster basecoats / mesh + superfine topcoat. Overall thickness of about 80mm less 25mm thick average thickness of old plaster = about 55mm loss of room space to external walls.

We could have gone for a thicker cork board to improve thermal performance but the condensation risks were too great.

The paints also need to be breathable so we’ve gone for Beecks mineral paint.

As can be seen the totally finished project isn’t complete but we are nearly there. We will be posting updates in the near future so please keep watching.

Hope this is useful and helps, thank you and bye.

[nickmorgan]

Thanks for sharing that, I'm considering something similar for my house. How did you calculate the condensation risk?

[gerigame]

i need to find somone around the Newcastle area that would do this. can you advice what to look for in a plasterer that woudl understand this? TIA

[jasonmorris]

Hi, very good video. Im just interested as to what method you would go with if doing stud wall ? Im struggling to find a plasterboard finish that would allow the wall to breath . Many thanks