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External insulation or not on sandstone house with modern extension

Discussion in 'Plastering and Rendering' started by Kaymo, 24 Nov 2017.

  1. Kaymo

    Kaymo

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    Hi,
    Sorry for the long post, but "it's complicated", well it's complicated for me anyway! :)

    I have recently moved into a sandstone house built in the 1800's, which has a modern extension on the back circa 1980's at which time a cement render was also added to 3 sides leaving just the front wall showing the original sandstone. The render is cracked and boss in numerous places and at some point will need to be redone - although i understand that it should be lime render on the sandstone. I am trying to make a longer term plan, considering other things that need to be done such as insulation etc and as planning won't allow me to cover the front sandstone wall I think that I would have 3 options:

    1. Remove the render on the sandstone parts of the wall and return to original (presuming stonework underneath is ok), re-render the modern parts
    2. Re-render all the walls, presumably with lime based render
    3. Fit external insulation, and then re-render

    If '2', and presuming that I am correct to say that it should be lime based render on the sandstone, my question is whether its ok to use the same lime based render on the modern brick built part, or whether this part should be cement based render with some kind of join between the two?

    If '3', then this is where I think it gets complicated. Firstly, would it look really odd having the rendered/insulated walls edged off near the front of the house, presumably protruding around 100mm or so, has anyone seen this done?

    Secondly, this would leave the front wall of the house uninsulated, or insulated from the inside. Are there any likely problems with this?

    Thirdly, there are some problem areas, such as one side of the extension that faces into next door's garden, that has quite an uneven surface and limited space to work - as per the pic below. I don't know if it would even be possible to insulate here.

    Basically I am just trying to figure out whether I should be considering external insulation, or with the combination of the fact that the front wall can't be insulated from the outside, and the other issues, whether I should just get someone in to render the outside normally and separately look at insulating from the inside?

    Thanks for reading war and peace and for any comments?


    2017-11-17 11.29.37.jpg


    Where the render is edged off at the front of the house below:
    2016-06-17 13.59.20.jpg


    Back of the house showing the 1980's single storey extension:

    2016-06-17 13.40.57.jpg
     
  2. endecotp

    endecotp

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    Is the building listed?

    It doesn't look very promising for external insulation to me, but you never know what some clever person might be able to design.
     
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  4. Kaymo

    Kaymo

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    The building is not listed. It is in a conservation area though, which means that approval to change the front of the house would be highly unlikely. However, as the rest of the house has already been rendered there shouldn't be a problem getting it rendered again. I believe that there is such a thing as insulated render (Bauwer) but doubt that this would be as effective as exterior insulation boards.
     
  5. Notch7

    Notch7

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    External insulation also means extending window and doors cills as well any issues caused by reducing roof overhang.
     
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  7. Kaymo

    Kaymo

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    There is no roof overhang or protruding cills on either gable, and I think the overhang should be ok at the back but there could be an issue with the guttering downpipe and the cills on the extension. This has made me think though about how insulation would be handled at the windows because there would still be a significant area of sandstone on the inside of the window recess that would presumably not be insulated. Hmmm not simple.
     
  8. DIYnot Local

    DIYnot Local

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