Old stone house made with granite blocks...protruding stones in attic and water coming in WWYD

[merrychristmastoall]

Our house was originally pointed up with lime mortar, and currently is partly pointed with cement (previous owner) and partly old lime mortar. The granite and the lime mortar breathes and so damp can come in and go back out.

On the top floor, some of the granite blocks protrude into the room and we decided to keep them as a feature, and so rendered and put up plasterboard with some foam backing for insulation on the walls, with the stones sticking out inside the room. Bad idea - the damp came through and discoloured the paint work around it, it looks awful.

As a solution which is cheap and quick, I want to put up a new plasterboard wall in front of what is there, ie put up a wooden frame to create new wall in front with a gap between protruding stone and the new wall, with a silver membrane thing which keeps moisture away from plasterboard (and provides some additional insulation)

My husband wants to take down everything which is there, and then do the same thing - membrane and new plasterboard wall on a frame in front of protruding stone

WWYD?

Neither of us want to remove protruding stone as we are concerned about structural impact, by the way

it's no good trying to block the water on the inside of the house

you have to prevent it penetrating from the outside

I suspect water running down the wall from gutter, downpipe or roof defects. the pointing may be contributory.

you say water, and you say damp. Which is it? Penetrating rain? Or condensation on cold stonework?

some photos would help.

piglet thank you for your reply - granite and lime mortar is very different from bricks and mortar - both granite and lime mortar are porous, and let through water, though not vast amounts. Inevitably there will be water coming in, and unless we cover up the stone with tiles on the outside or render, which we don't want to do, water will come in and leave too via the wall. It makes it hard to know how best to insulate. You asked about damp or water coming in, I am not sure, I think I meant water coming in re the stone - we also have damp I think because there was no damp course put in on the ground ... different issue? My knowledge of all this isn't extensive.

When I say water comes in through the granite is feels damp to touch and changes colour, but water doesn't flow into the house.

Water/damp doesn’t damage the stone, but will damage timber, felt, insulation, plaster etc. We were told similar re: our fireplace, it’s not a “problem to be fixed” so much as something to protect damageable things from.

Check the damp is only from porous stone - Is the pointing in good repair, also gutters, roof etc? Sort out rising damp if needed.

Do you have membrane between stone and any timbers (including structural ones?). If not surely your timber will develop wet rot (followed by dry rot)?

Decor wise : could you leave the whole wall clear of plaster?