Is this Lime based or Cement based render?

Discussion in 'Plastering and Rendering' started by emzd, 22 Mar 2017.

  1. emzd

    emzd

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    Hi everyone,

    I would really appreciate some help in trying to figure out what type of render is currently on my house. . It's white and bumpy but very smooth. I'm struggling to work out if its a cement based or lime based render (with aggregate causing the bumps)? I have one patch of damp coming through behind the downpipe, and really need to know what type of render it is to repair it.

    I thought it may be lime as it leaves a white residue when you touch it, but I don't know if it could be cement just covered with a lime or other type of wash? People have suggested it may be tyrolean, but the aggregate seems big for tyrolean?

    I've attached some pics of the front wall, and also of an area of wall behind the downpipe. The area behind the downpipe seems to have eroded due to the water- another reason I thought it may be lime. I don't know if cement would erode in this way?

    Any ideas on what is is, or what to use to repair the damaged area would be greatly appreciated!

    Thanks very much,
     

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  3. chris1982

    chris1982

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    If you break off a little and put in some tap water, does it bubble? If so, it's likely to contain some lime.
     
  4. vinn

    vinn

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    It looks like badly mixed & applied Tyrolean.
    True Tyrolean doesn't have aggregate in it, & usually is a cement mix. There are variations in the mix however.
    Take a little loose render and pulverise it with a hammer - look for stone or chipping.
    The paint should be a masonry paint - true (breathable) masonry paints are a kind of limewash. Your paint is so smooth its perhaps a plastic paint
     
  5. emzd

    emzd

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    Hi Chris- thanks I'll try some in water tonight and see what happens.

    Vinn- Thanks for the advice. I chipped some of the white layer away and the bumps appear to be small stones, maybe with some kind of wash over the top.
     
  6. Nige F

    Nige F

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    Pebbledash ?
     
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  8. vinn

    vinn

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    OP,
    There seems to be more than "some kind of wash over the top" - I suspect that the background has had more than one remedial layer of materials over the top so to speak.
    Given the unevenness of the surface I'd also suspect the background?

    To repair behind the down pipe you will have to remove (replace?) the pipe, and hack off the old material to expose the background, and then start a vertical patch from there. There are a number of posts on here about patching dash/render.
    Whether you have cement or lime in the existing render mix its best practice to use a sand and lime mix for any patching.

    Before doing anything else, it would be worth your time to carefully examine all similar surfaces for cracks or hollowness or bulging.

    Is the house stone or brick?
    Perhaps post a pic showing the penetrating damp signs on interior walls?
     
  9. clive12345

    clive12345

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    It looks like "wet dash " also known as "roughcast" .
     
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  10. vinn

    vinn

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    Good call. Thats probably what it is.
     
  11. emzd

    emzd

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    Thanks Vinn for the advice about repairing the damage behind the water pipe- thats really helpful!

    Its an old stone house built around 1850, and the walls are approx 18 inches thick. Local builder today said it looks like a cement roughcast with riverstones and paint on top.

    As soon as I have a picture of the damage inside I'll post it. The joints of the house are all filled with earth, and the plaster on the inside has many layers. Looks like lime and then multiple layers of pink gypsum over the top. Thinking about taking all the plaster off downstairs and replacing it. Would it be awful to put a sand and cement mix back on the inside means as there's what looks like cement already on the outside? I know old buildings are supposed to breath, but if cement is on the exterior, would having internal lime plaster just encourage more moisture to enter the walls and not escape outside?

    Thanks everyone
     
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