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  1.  
    Hi all

    I'm making a start on removing the thick plaster, etc on the internal walls of the old part of my house. I can't be certain, but I think it would have been applied in the mid-1970s. It's really thick in places - up to 50mm/2 inches. I'm hoping to clean the stonework up afterwards and re-point (with lime) if needed. Prefer the natural look, and love the history of the place. Prefer a cold bedroom too before anyone mentions insulation ;)

    While working the hammer and chisel, questions have been coming up in my head...

    - I'm curious as to why the "scratch coat" (is that the right term?) would have been put on so thick?
    - Can anyone tell whether it is basic sand and cement or something else?
    - Might it have had some kind of damp proofing element?
    - Are there any downsides to removing it (I appreciate something will need to be done where the ceiling meets the wall)?
    - Any tips on how to clean up the front of the stonework easily? At the moment I'm just using a wire brush, but hoping for a less labour intensive and more effective solution!

    Any comments most appreciated.

    Cheers
    • CommentAuthorgreenfinger
    • CommentTimeJul 13th 2021 edited
     
    Photo 1
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    Photo 2
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    Photo 3
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  4.  
    The wall looks like a stone / rubble wall, that is stone on either side with rubble/earth infill.

    Over here the rendering would be a sand/ cement / lime mix but I can' speak for where you are. I would suspect the same or sand / cement with a plasticiser for workability.

    The render has a number of jobs, one is to stabilise the outer surface, that is to stop bits falling off and out from the infill, another is to stop ants and mice coming through the wall and a third is to stop the howling gale that will come through if it is not rendered.

    It is usually thick in places because this type of wall is usually far from straight and the render is a way of making it flatter.

    If it were mine (and I have a couple of houses built like this) I would leave the render if in good condition or re-render if it was in poor condition. Pointing with lime will be a labour of love and I'm not sure how long the pointing would last. When such walls are rendered over here the first part is to throw a cement wash over the wall to provide a key for the render and then the render is thrown on to the wall and then floated as you go. The tools are a "spoon' about 1 ltr. capacity which is used to throw the render with a flick of the wrist and then a plasterers float to smooth of as you go. The render needs to be thrown on otherwise there is insufficient penetration between the stones which will affect the adhesion and stability of the render.
    • CommentAuthorCliff Pope
    • CommentTimeJul 13th 2021
     
    I'd be very cautious about hacking off that rendering. It's not in my view terribly beautiful stonework once exposed, and in my experience a few centuries of gradually built up render/plaster/whitewash etc contribute greatly to the security of the wall. Pull it off and you risk the soil inside the wall trickling out through the gaps between the stones.
    I also found areas where there was no stonework at all, just very fragile long-dried mud, mixed with straw, bits of twig, and a mummified cat.
    •  
      CommentAuthorfostertom
    • CommentTimeJul 13th 2021 edited
     
    I wouldn't be put off, if you're prepared for the work!

    There will be surprises, but if the wall's stability is relying on 'structural plaster' then it's gd to know about it! If there's cement render then it's modern-ish and there was a previous, less brutal finish before that. Still as Cliff says it's not v beautiful, and 'natural rubble' finish can be quite overpowering.

    I'd lime-point but not to visible standard, finish with a thin maybe lime coat that doesn't try to be smooth but results in a surface that follows every irregularity, slightly softened.
    • CommentAuthorgreenfinger
    • CommentTimeJul 13th 2021 edited
     
    Hmm, some slightly scary responses there, with a calmer leveler from fostertom at the end! All the same - thanks for all of the replies and input.

    Posted By: Peter_in_HungaryOver here the rendering would be a sand/ cement / lime mix but I can' speak for where you are. I would suspect the same or sand / cement with a plasticiser for workability.


    That's what I thought but really wasn't sure. I'll post some photos showing a close up of the plaster/ and sand/cement(?). I've done some with the flash on and some with it off.

    Posted By: Peter_in_HungaryThe render has a number of jobs, one is to stabilise the outer surface, that is to stop bits falling off and out from the infill, another is to stop ants and mice coming through the wall and a third is to stop the howling gale that will come through if it is not rendered.


    Would re-pointing not solve all of those things? Also, you mention below that pointing in lime might not last... Why might that be the case?

    Posted By: Peter_in_HungaryIt is usually thick in places because this type of wall is usually far from straight and the render is a way of making it flatter.


    That makes sense and I did wonder... With there being innie and outie stone, I guess you have to render to the outies which means the innies will have a lot more render.

    Posted By: Peter_in_HungaryIf it were mine (and I have a couple of houses built like this) I would leave the render if in good condition or re-render if it was in poor condition.


    The render is in good condition as far as I can tell. However, I prefer the aesthetic of bare stone. And more importantly I thought the idea was to allow the wall to breath? There is a concrete render externally which we are going to remove and is seemed a bit daft to do that but then leave a thick non breathable inner render.


    Posted By: Cliff PopeI'd be very cautious about hacking off that rendering... in my experience a few centuries of gradually built up render/plaster/whitewash etc contribute greatly to the security of the wall. Pull it off and you risk the soil inside the wall trickling out through the gaps between the stones.



    So far it would seem that there is not such a "build up". It seems the render goes right back to the stone. Granted some of the "pointing"/infill is crumbly but would that then not be dealt with by re-pointing (and would that also not stop soil or whatever trickling though?)

    Posted By: Cliff Popemummified cat.


    Yikes! Not sure what the dog would make of that!


    Posted By: fostertomIf there's cement render then it's modern-ish and there was a previous, less brutal finish before that.


    Yes, I think it is cement render and will post some pics. No signs of an underlying render though, so perhaps there never was one or it was removed prior to applying the current render??


    RE: aesthetics, etc. I really like the look; or at least I will when it is done. We did the same to the fireplace wall downstairs and I love how it came out. In the photos above, the stone has only been through phase 1. More phases of cleaning up and it will start to look a lot better. A least to my eye.

    But I don't want to inadvertently cause problems, so I am listening to what's been said and welcome any further thoughts....

    ....I don't want the wall to collapse! And in addition, I should add and ask - the floor joists that go into that wall are already undersized. Could removing the render (will be doing the same in the room below) weaken the joists by removing an inch or two of "support"?

    Thanks for the fantastic help.
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  8.  
    We did something similar in our home. We took down the plaster board on an internal wall that had a damp problem at the base. The gypsum plasterboard was dot and dab fixed onto the stonework and was relatively easy to get off. The main problem was removing the dot and dab plaster. We just got the wall sandblasted and it came up really well. I then lime pointed the wall, which is quite a nice material to use for a novice as you can take your time to get it right because it takes so long to go off. Once it goes off, you just brush off the excess.

    The photo below shows the wall after it had been sandblasted and then lime pointed. The white area at the bottom of the wall is a lime plastered parge coat to make the wall air tight as I fitted a radiator there. The combination of the lime pointing/plaster and the radiator means the damp problem has been eradicated.
      feature wall.jpg
  9.  
    The render on walls such as these is not structural in that it is not load supporting but it is stabilising. Without the render if you wanted to demolish the wall you would start at the top and just pull the wall apart - no tools needed. With the render you would need a hammer to dislodge the outer layers as you go. Your wall is held together by gravity !

    You can see in the last photo you posted the small stones between the larger ones, it is these smaller stones that the render holds in place and they are integral to the stability of the wall. If you haven't found out already you can't make a small hole in such walls. Even putting in say a loo vent will result in a sizeable hole and care has to be take to minimise the amount of rubble infill that will fall out. Further these walls do not like hammer drills, they tend to shake the wall apart especially with the larger diameter bits. Attaching things (shelves) to these walls can be difficult depending upon the type of stone and generally it is the render where you can plug and screw.

    The render on these walls is important and if your outside render is sound I would leave it alone. Hacking off sound render will cause some damage to the wall. Very much - if it ain't broke, don't fix it !! On the inside face of the wall if you want feature stone I would select a few randomly placed large stones and leave them unrendered by steeply feathering in the render around the edges.

    Edit to say cross posted with pile-o-stone. The wall shown by pile-o-stone is a different type of wall to that shown by greenfinger. P-o-S wall is more like a normal brick wall rather than a random stone rubble wall of greenfinger so different options would be available to P-o-S.
    •  
      CommentAuthorfostertom
    • CommentTimeJul 14th 2021
     
    All excellent. Those slabs of cement look disgusting - old stone/brick just loves to get some 'fresh air', usually looks good, or at least is ready for a gentler, more traditional finish.
    • CommentAuthorMike1
    • CommentTimeJul 14th 2021
     
    On the basis of the photos posted so far, I can't see a problem with repointing it. Make sure the joints are raked out to a good depth, so that the new pointing isn't just superficial. Also look out for large joints which may once have had smaller stones wedged in them for solidity, and replace them (they may have been lost at an earlier date - when the wall was first cement-rendered, for example - rather than during your hacking off now).
    • CommentAuthorJonti
    • CommentTimeJul 14th 2021
     
    I too have removed the render of one of my croft rubble stone walls. I repointed it with lime which does take time but the end result is very pleasing. If you like the look I would go for it.
  10.  
    Just to add, don't be afraid to take out and replace some stones if they look a bit crappy. In the wall that I screenshot I replaced a few stones that had cracks down them or that were at an angle that made the wall look hollowed out.

    I got some replacement stone from our stream, where they were black from weathering, but when I split them to shape them into rectangles they looked great.
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