Drylining stone walls

L1011

I have a ~200 year old, non-listed, rubble stone house; which has lime whitewash on the external facing but does have cement plaster on the walls in most rooms - bar one, which is dry lined.

I don't appear to have any specific issues with damp from that; but do have a Dimplex 20L/day drained dehumidifier running 24/7; and a thermostat set to 13C with twice weekly kicks to 19C so the place is being heated and dried even when I'm not there.

Now, I know dry lining inside rubble stone is seen as a Bad Thing, but so is cement plaster… Would I be mad to dryline the bathroom? It's much colder than any other room in the house, partially due to poor or no attic insulation - I can't check this as there's no hatch to the attic on this section, the walls reach the roof trusses.

I need to replace the toilet and want to replace the sink anyway so they'll be off the wall, and the existing plaster is in appalling condition - salt efflorescence breaking up the surface because someone made it with beach sand, plus two years of no heat/use over the pandemic; looks like it was applied in the dark by someone who didn't know what a level surface was etc etc.

The shower cabinet is already built up about 60mm off the outer wall which I suspect is some form of dry lining too, as it was replaced in the past 15 years.

Would look to hack the ruined plaster surface back a bit, batten and insulated board on the two external walls and leave the two internal as is; have to figure out what to do about finishing the edges around the window; install new toilet/sink.

Merrion

Maybe a breatheable surface - for a bathroom I would use a lime plaster and cork mix like Diasen Diathonite ?

L1011

Should probably add that I'm absolutely appalling at plastering (and tiling), even skim coating the plasterboard would be a push. So using a heavy insulated plaster may be beyond me.

Forgot there is a second reason for the comparatively cold - the house is slightly dug in to a hill, and the other stone section rooms either have a block extension behind them, or a larger area before the retaining wall so there isn't much sun/heat hitting this one.

Merrion

Maybe you need to get someone in to do the lime plastering?

(It's not that hard really - you can always sand out any imperfections after it dries)

The thing is that moisture will get through the stone wall and push off anything impermeable you put on that wall eventually so you will be best off doing it once well?

L1011

Further thing to add - its on an island. Trades are impossible. But it may be something I need to just do.

The external lime whitewashing is a hideous job that needs re-doing particularly as one section got very wet due to a bad gutter (since replaced entirely); but I was forced to learn how to mix and apply that as a teenager so can probably dig the repressed memories up!