Worried about insulating an old house

[oldbilly]

Hi All.

I recently bought a three-storey, mid-Victorian house on the coast with solid brick walls finished with lath and plaster. It needs a bit of doing up (including an injected damp course) and the builder is keen on adding internal insulation. His plan is:

Remove lath and plaster.
Clean up internal brickwork and add PVA.
Dot and dab 80mm insulated plasterboard.
Treat external brickwork with weatherproofer.

I'm in favour of insulation in principle, and the builder is certainly knowledgeable about local houses and conditions and has done this to other properties. OTOH a lot of heritage/traditional house sites tell you not to do this sort of thing, because you're turning a breathable wall into a non-breathable one and you may get all sorts of issues down the line.

Frankly it's hard to know who to listen to. Does anyone have thoughts on the matter?

Cheers!

 

[JohnD]

It needs … an injected damp course...

that's improbable. What makes you think so?

 

[foxhole]

that's improbable. What makes you think so?

Probably been told by dodgy builder or damp proof company.
I would never use weatherproofer on brickwork , big cause of damp , moisture still gets thru cracks and mortar but then can’t escape.
Walls don’t have to be pva’d you can foam fix , way quicker and cheaper than dot and dab.

 

[Gerrydelasel]

because you're turning a breathable wall into a non-breathable one and you may get all sorts of issues down the line.

That's more of an issue when you put gypsum plaster straight onto brick (where lime plaster used to be). Plasterboard will have an air gap behind it, so the walls shouldn't mind the change.
Don't even think about an injected DPC (what is this, 1990?), instead make sure your underfloor ventillation and external ground levels are good. Do not paint anything onto the outside of the brick, no matter what wonder-material they claim it is. Make sure they use lime mortar for any repointing.

 

[Deleted member 174758]

I you have the space for dot and dab you may well have the space for Gyplyner which, because the boards have very little connection to the walls (unlike dot and dab), has better heat and sound insulation properties