Repairing lime plaster...anyone in the know?

[phil24_7]

I am currently renovating 2 of the bedrooms in my house. It is a double fronted, semi detached Victorian house and I have knocked down the lath and plaster dividing wall between the two rear bedrooms. It has obviously been repaired several times in the past as there are several types of gypsum based plaster in various places around the room.

It is obvious that the two large windows must have rotted out many years ago as both the sections under the windows have been built up using a cement based plaster, the plaster between the two windows has some evidence of minor dampness, some old, some current and some that has been patched with cement.

The party wall side (left side of the house) is in good condition apart from a few poor repairs using cement, these include one of the wooden edgings being redone in plaster whilst leaving the other!

The opposite chimney breast had been re-done with modern gypsum as had both of the alcoves.

The alcove to the right of this chimney breast more or less disintegrated when I started to remove the gypsum as it had blown due to moisture in the wall, the alcove on the other side has been completely repaired with cement, this goes around the corner and up to the window and is so hard, even a percussion drill, set to hammer only and fitted with a chisel wont break through it very easily.

I know the plaster on the outside of the walls must have some damage or cracks in it (although I can't see them as they're pebble dashed) to allow the moisture into the walls and I was originally planning on redoing all walls except for the chimney breasts in lime plaster to allow the walls to breathe. I'm not sure whether I will be able to remove all of the cement based plaster to allow this to happen, even if I can, I'm not sure whether it will damage the stone walls or not.

This leaves me in a bit of a pickle. Do I:

1. Try to remove the cement render and then get all the walls lime plastered and then paint with breathable paints

2. Leave the cement plaster and lime plaster the remaining walls, then paint with breathable paint

3. Do all the walls with a cement based render and skim with gypsum plaster then paint with whatever the hell I want.

Option 3 would almost certainly mean that I need to re-render some of the outside of the house to stop moisture getting in. This wouldn't be the end of the world as I am having a side extension done this year so could do the side of the house at the same time (would also externally insulate at the same time) and then do the rear of the house when finances allow.

So those in the know...what do ya think?

Thanks in advance

[phil24_7]

Nobody?

[MisterTommyH]

The only thing I know about Lime products is when we've had to look at Lime mortar for specialist projects. I know it's a pain in the ****, I don't understand it but do know that the curing periods are stupidly long and very dependent on temperature over a long period of time. Personally I'd avoid it like the plague.

[tinpants]

If it was me I'd probably stud the walls and put moisture proof (coloured green) plasterboard then skim over it. You may get away with dotting and dabbing the boards on to save time and space but whatever you do you need to get all the gypsum off the wall to allow it to breathe and dry out. I would only put lime plaster back on if there was a planning issue. As has been said before, it's a reet pita and has ridiculously long curing times. If you want any more advice give me a ring. You have my number I believe?

[phil24_7]

I really don't want to plasterboard the room so that is out. Not too bothered about the length of time the plaster will take to dry so it's really between the 3 choices in the OP. Not sure I can get all the cement of safely so it somehow seems foolish to lime plaster the rest of the room if I can't do all the external walls but I also don't really want to cement render over a stone wall. I think this may be the easiest thing to do, just as long as I render the outside of the house reasonable smartish. Why do old houses have to be so awkward!

[Tom_the_great]

From a paint point of view i would say 3, why?

1. Many of the 'Big' Brands do not make paint suitable paint for this so you will pay more or be falsly sold paint that willl fail.

2. Breathable paints are very chalky and mark very easily, Thus meaning more work in the long haul.

3. you cant use many paint finishes such as solvent based or acrylics so any form of tough finish is also out. so if you wanted it for a bathroom or kids room lots of maintenace is going to be a killer!

Hope this helps

[phil24_7]

Don't care about the paint really as I have found some decent looking breathable paints but I'm leaning towards option 3 myself at the minute, even though my heart says option 1!!!

[Nobbylad]

If I understand correctly, you're assuming you're getting moisture into the walls and interior finish due to issues with the external rendering?

Isn't it the case that any moisture absorbed by the external rendering would evaporate the same way and shouldn't get through to the internal walls? Is it a cavity wall property? If so, the issue is almost certainly nothing to do with the outer skin, regardless of finish, but more likely damp from another source i.e. bridged cavity, leaking windows, poorly ventilated chimney stack.

Apologies if I've misunderstood.

[phil24_7]

Aye, right script, wrong page!

It's a Victorian house with no cavity walls. The walls will naturally hold moisture, it's what they're designed to do. In the summer, this moisture should work it's way out. The problems start when people start coating the outside in cement based, unbreathable renders. If there are any cracks or other damage to the external render, water can get in but can't get out. This means it migrates to the inside of the house.

There are a few moisture (not quite damp) problems in the house due to the poor quality and upkeep of the external pebble dashing so I'm just trying to sympathetically upgrade my house. This has become more difficult due to some internal walls being repaired with a very strong mix of cement render/plaster meaning any traditional/sympathetic work I do will not cover all the walls as I don't think I can safely remove this cement.

Hope that clears that up?!

[Nobbylad]

Yes it does. Thanks for that. ..every day is a learning day!