Lining old 1920s plaster (and lathe) walls

[MrMark]

Doing up a 1925 end terraced house. Brick dual block with cavity. External wall covered with pebble dash render.  It’s had no heating in for two years. Not a cold or damp house and is well ventilated. Ceiling/floor timbers in good nick. Only point of rot on a couple of timbers including wood lintel on external (non adjoining wall).

 

We’ve batoned over the old plaster/lathe walls with 25mm batons to be lined with a mix of standard and soundbloc plasterboard. For the outer walls we have conflicting advice:

 

- As it’s a ‘dry’ and not damp house, and there’s render on external wall faces, we don’t need insulation behind the batons. Don’t need to worry about condensation as dew point will remain in the well ventilated cavity. 

- Rockwool or similar behind the batons. Provides a some extra warmth. It’s breathable and permeable so condensation shouldn’t be a problem and will be in the cavity wall anyway. 

 

- Rockwool with something like intello plus behind plasterboard. Expensive option for a 1920s house but negates and concerns of dew points ingressing closer to inner wall. 
 

I’m aware of overkill and don’t want to be living in a sweat box or feel like we’ve created a home in a polythene bag! We’re after some middle ground.

 

The internal walls are much easier. 
 

Would appreciate any words of wisdom or advice as we havent dry lined outer walls before.