Internal Plastering very old stone wall

[GaryD007]

HI all

I am gonna be a father come June and am planning to re-do the back bedroom as a nursey. As I suspected the wall with the window has extremely crumbly old plaster (its a 140 year old Terrace) . This wall is made up of extremely thick and really un-even stone (I know 'cos I redid the bathroom a few years ago).
I was thinking the best (and quickest) approach would be to strip the plaster off right back to the stone and PVA the surface. I was then going to glue up 12.5mm plasterboard and skim coat it.
Is this the best method ? I am on a budget and am going to do the work myself. Should I use foil-backed plasterboard or just normal stuff? (The room is North facing so gets no direct sun) I am planning on getting a good smooth finish ready for painting over after it has been skimmed.

Thanks in advance for any advice offered. - Gaz

 

[thatbloke]

what is on the other side of the wall? some of these old houses dont benefit from being 'sealed' as they are designed to breath.

this is a good place to look for advice on older property's.

http://www.periodproperty.co.uk/forum/viewforum.php?f=1

 

[GaryD007]

thanks Thatbloke

the other side of the wall is exposed to the outside world. Would it best to not PVA the stone and just glue the plasterboard directly to it ?

 

[Richard C]

I am gonna be a father come June and am planning to re-do the back bedroom as a nursey.

Congratulations Gary.

As I suspected the wall with the window has extremely crumbly old plaster (its a 140 year old Terrace) . This wall is made up of extremely thick and really un-even stone (I know 'cos I redid the bathroom a few years ago).

Solid walls don’t like modern Gypsum plaster as it doesn't like the slightest damp & doesn't breath. Your existing walls are probably lime plastered, you can re-plaster & this came up very recently in these two topics;
//www.diynot.com/forums/viewtopic.php?t=210788
//www.diynot.com/forums/viewtopic.php?t=212273
It is a bit specialist & I’ve never personally done any so don’t really know if it’s any more difficult to use than Gypsum plaster; others will advise I’m sure.

I was thinking the best (and quickest) approach would be to strip the plaster off right back to the stone and PVA the surface. I was then going to glue up 12.5mm plasterboard and skim coat it. Is this the best method ? I am on a budget and am going to do the work myself.

Don’t fix PB to solid external walls without first researching correct methods & insulation possibilities if you need any; going about it the wrong way could end in damp disaster. Start by reading the archive posts on this forum as there isn’t much that’s not been previously covered.

Should I use foil-backed plasterboard or just normal stuff? (The room is North facing so gets no direct sun)

Foil back can be used as a solution but you can’t dot & dab it, battens only unless you mechanically fix (screws) but research as above.

 

[thatbloke]

have a look through the articles section here , its a good place to start.

http://www.buildingconservation.com/

lime plastering need not be specialised , you just need to figure out what is best under different circumstances , if you are doing it your self you will be a specialist in these particular circumstances , in other words you dont need to be a professional, you just need how to find out how to do it properly.

that forum link would be a good place to start as would the above link. you old house is a totally different ball game from newer buildings.

 

[GaryD007]

Thanks guys

Lime plastering seems like a lot of heartache. The info in the links also mention that you can't paint on lime plaster (can only limewash it). This is a bit concerning seeing as it is going to be a nursery.

I think I will research into fixing battens and screwing up foil-backed PB with a skim coat. This way the wall should still be able to breathe without the PB getting damp.

The way I did the adjacent bathroom (same external wall) was to batten the wall and fix marine ply which was then PVA'd and tiled.

Can marine ply be finished with a fine skim coat?

BTW the wall used to be damp due to a leaking gutter which was dripping down behind crumbling external render. This was all removed and the guttering replaced (about 5 years ago) and now that wall seems bone dry.

 

[Richard C]

Lime plastering seems like a lot of heartache. The info in the links also mention that you can't paint on lime plaster (can only limewash it). This is a bit concerning seeing as it is going to be a nursery.

That’s what allows the wall to breath.

The way I did the adjacent bathroom (same external wall) was to batten the wall and fix marine ply which was then PVA'd and tiled.

You don’t need to use marine ply, it’s too expensive; WBP is made using the same waterproof adhesive to bond the veneers but doesn’t have the expensive finish veneers. But I wouldn’t use ply to line walls, particularly in a bathroom. Ply is timber which is not dimensionally stable when it becomes damp; WBP/marine ply won’t delaminate but it can still warp. Also, never use standard PVA under tiles; it can cause adhesion problems, remains water soluble & could result in your tiles falling off the wall in wet areas; if you need to prime before tiling use a waterproof SBR based primer but always follow the tile adhesive manufacturer’s recomendations.

Can marine ply be finished with a fine skim coat?

No, you can’t plaster over wood, it’ll fall off. I would never use ply over walls, particularly solid walls where damp could penetrate; there are other far more suitable solutions. Solid walls must be allowed to breath but if damp is a problem, you can fix boards, either Duplex or Thermaline, in front of but not on it.

 

[GaryD007]

hhmm thanks for your advice Richard

found some more food for thought on this link

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=241

 

[thatbloke]

you can use clay paint on lime plaster , among others.
lime wash can be a very nice finish as well.

have a look here.

http://www.mikewye.co.uk/

putting on a coat of lime plaster will be less ache than having to sort out damp problems in a nursery or having to rebuild a wall that has blown apart by frost due to water ingress.
at the moment i am having to rebuild a kitchen extension that has disintegrated due to walls and floors that were designed to breath and evaporate moisture being sealed up with cement plaster and cement screed.
its expensive , time consuming and a real pain in the arse.

 

[sjwood0]

Hi All

For the benefit of people googling this here's how I did this. They'll be better advice than this from more experienced people than myself but here's some advice from a DIYer who had only done a bit of gypsum plastering previously which is closer to the stage that most people will start at.

Method.

• 
  1. Remove the old plaster from the wall using a bolster chisel and lump hammer.
  2. Repair and replace old stone work that was missing or got damaged by taking the old plaster off. In my case this was a mix of lime and gypsum plaster. Use lime mortar for this not cement based mortar as it is breathable. Taking off the cement plaster was more difficult and was on the areas that were damp.. hence the reason gypsum plaster is bad news in old stone built houses.
  3. Where (and if) you will be reattaching a skirting board to the wall and if not there already add some thick blocks of wood at roughly 2ft intervals at floor level within the stone wall. Mark on the floor where you have positioned these for when the blocks are covered over with plaster. These are needed for screwing or nailing the skirting boards back to the wall as the vibration doing this could loosen plaster on the finished wall.
  4. Apply some plastering metal mesh (the sort you can get at wickes etc) to any bits of the wall that are very smooth e.g. a large oak lintel above a window frame. This provides a better key for the plaster to stick to.
  5.Wet the wall with a spray water bottle just before you plaster. Porous bricks will require this to be done several times in the hours before as you need to limit the speed at which the wall sucks the moisture from the plaster.
  6. Apply the first coat of 'coarse stuff' plaster. I brought this ready mixed from the supplier near me in the link at the bottom but other specialist builders merchants will sell it. It contains small bits of grit and horse hair to increase the strength of the mix. You can either apply this by harling (throwing it on) by a (gloved) hand or using a special trowel. I did this a bit in the places I found hard to reach or where there was more of an indentation. This method is meant to provide a better cover as more air pockets are eliminated but for areas where you are able to press on firmly using a standard plasterers trowel then newbies may find it quicker. Even at this stage you should be attempting to even out undulations in the wall but note that if you put on the plaster too thick (e.g. an inch) then it will crack as it drys.
  7. Once that's on and it's started to set a little scratch crossed lines in the plaster, this provides a key to the next coat. Use something a little wider than a knife blade that will be produce lines that are too fine to provide a proper key.
  8. Next is to apply another coat of coarse stuff this time applying with a trowel and playing far more attention to the undulations in the wall. Again before you do this spray the wall with water to control the suction of moisture from the new plaster. If the first coat was the 'dubbing out' coat the second the 'scratch coat' then some people refer to this as the 'float coat'. I used a long plank of wood and frequently held it against the wall to see where the dips and bumps in the plaster really were. Doing this method gives you a reasonable/rustic finish suitable for an old 1600's house. If you are after flat walls however then you need to apply screeds (long thins vertical strips of wood) at regular intervals and skim the plaster between them, removing them afterwards. You may also need to pad out the screeds in some places and check out there straightness with a plumb level. when the coat is done scratch crosses in the plaster once it's started to set but make sure they're much finer lines. If this coat does not give you the flat wall you desire repeat this step with another coat.
  9. Wet the wall again and you're now applying the 'fine stuff' plaster to the wall. This has a creamy texture and is very satisfying to work with as it's similar to gypsum plaster only it gives you more time to work with it (like the coarse stuff plaster too). Use all your reach to do long skims with your trowel and make sure that you leave the wall with no imperfections that you would not be happy to paint over - you don't have the option of sanding lime plaster so it is less forgiving in this way.
  10. As far as drying times goes leave approx 2-3 days between coats depending on the room conditions. You should be trying to create a moderate-cool temperature so the plaster sets slowly. You should not lime wash or apply clay paint to your wall for around 5-6 weeks after the final coat. Note the types of paint specified, you've gone to the effort of lime plastering your wall so it is breathable so use paint or wallpaper that is also breathable for a more healthy damp free environment!

Here are the products for Coarse stuff, fine stuff and the paint, other suppliers are available..

http://www.womersleys.co.uk/acatalog/Building_Products_2_6.html

I hope this proves useful to someone.

Steve

 

[roughcaster]

What a great post,, very very useful, thanks for that.

 

[johnsennac]

I have the same problem with a 300 year old sandstone lime mortared walls 90 cm thick on my French barn.
I usually clean down the wall, removing all old lime plaster, and flatten any protruding stone using a diamond double row cup disk and/or chisel. Once the wall surface is reasonably flat re doors and window quoin-stones.

I find advice on the techniques of lime plaster


***deleted

are onlline.

 

[Stevieguy]

Hi Steve (SJwood0) ... that was a great concise post. Need to do same on old house I've bought in cheap Spain but needs complete reform Can I just ask what the three different layers were .. The you said was lime mortar and exactly what the other two layers skimming etc?

Steve