Damp, cold bedroom wall with serious condensation problems

Discussion in 'Builders' Talk' started by Alicegal, Aug 9, 2019.

  1. Joe the Plumber

    Joe the Plumber Active Member

    The trouble with the cement is it isn't breathable, so any water getting trapped behind it can only go inwards.

    If you'd like to post a photo of the outside, we may be able to offer more thoughts.

    Please keep us posted. This is all very interesting.
     
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  2. Dam0n

    Dam0n Active Member

    The worst thing he could have done really. If any water gets behind the cement it'll just hold it rather than let it evaporate.

    If it's fairly fresh on id be tempted to remove and repoint with lime. A limewash or two after might help it look nice and hide any rough repointing.

    If you do this don't use hydrated lime from the builders merchants. This isnt the same thing as hydraulic lime. This is an easy mistake to make and there's a BIG difference between the two.

    Good luck and keep us updated.
     
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  3. glob@l

    glob@l Active Member

    He also had a vapour barrier!

    On a seperate note, it's my understanding if you point a stone wall with cement any water trapped within will find it's way out by the easiest route. Since cement is stronger the stone the stone will become the sacrificial part of the structure, lime mix is weaker than stone and so it becomes the sacrificial part.
     
    Last edited: Aug 11, 2019
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  4. Alicegal

    Alicegal Member

    I'll take some photos this afternoon.
     
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  5. Joe the Plumber

    Joe the Plumber Active Member

    Great, thank you. I get lime mortar from here:

    https://www.lime-mortars.co.uk/

    Remember, the only thing you mix it with is water. No cement, whatever anyone tries to tell you!
     
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  6. Alicegal

    Alicegal Member

    Right, grabbed some photos. One shows the front of the house, where you can see the offshoot (housing the bathroom and kitchen). The other three photos show the back and side of the house. Above the offshoot, you can see the cemented wall (my daughter's bedroom). It's difficult to access this wall as you can see. The cement looks in fairly good condition. I've also atrached a photo of my daughter's bedroom wall where you can see the bulging plaster which, upon pulling back the lining paper, reveals crumbing plaster. I really hope leaving it and insulating the internal wall will solve the problem!
     

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    Last edited: Aug 11, 2019
  7. Mr Rusty

    Mr Rusty Well-Known Member

    I think there are two issues here. 1) the concrete render. IMHO a mistake on an old wall. It will be trapping moisture in the wall, however you are where you are. 2) condensation on the cold wall coming from inside. Think about making the structure functionally the same as a timber frame house. The inner structure is a timber insulated frame, then there is an airspace, then a brick/cladding structure. I agree making a stud wall inside is the best option here and create ventilation into the gap from outside by inserting an airbrick. If you use insulated PB on top of the stud, it incorporates a vapour barrier. The external side of the stud just needs a permeable membrane to keep any additional insulation between the studs in place. Remember the vapour barrier MUST be on the warm side, not the cold side of the insulation - on insulated PB it is between the PB and insulation.

    By sealing the room from the void between insulated stud wall and structure, any water vapour created by living won't get to the cold surfaces. You will still need to ventilate your living spaces, particularly where you are creating lots of water vapour.

    My experience is that although I am a DIY builder, I was trained in condensation control methods as part of my studies in the merchant navy. The thing with condensation is that it can be scientifically predicted. If you know the relative humidity of the air and you measure the surface temperature of a structure, you know if condensation is going to occur or not.
     
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  8. Alicegal

    Alicegal Member

    Thank you. I'm taking all your advice on board!
     
  9. Joe the Plumber

    Joe the Plumber Active Member

    Thanks for the photos. That's a genuinely lovely house. Incidentally, the photos are giving away your location. That's fine, but if you want to remove that information as this is a public forum, I wouldn't blame you.

    A quick observation is that the bottom slate on the front right has slipped into the gutter. This has left the top edge of the render
    exposed to potentially allow water to get behind it. It's hard to tell what's happening further up the end of the roof, but it does look a bit
    ragged. And of course we can't see the back elevation.

    With there being various other places the render has been penetrated (the overflow pipe and the cable fittings), those could also
    be allowing rainwater to get in.

    I also wonder if there should be some form of lead flashing at the bottom of the render where it meets the lean-to roof.
     
  10. koolpc

    koolpc Well-Known Member

    I woukd say, looking at your pics, especially the bulging plaster, that it seems like water is penetrating that cemented wall. Either through cracks or from the top edge by the slates.

    You need to sort this out first before you insulate
     
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  11. Alicegal

    Alicegal Member

    Thanks Koolpc and Joe the plumber, that's very helpful indeed. I'm noting everything you've brought up and will try to find a local builder to help us sort things out.
     
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  12. Joe the Plumber

    Joe the Plumber Active Member

    Make sure the builder knows about period buildings. Many of them haven't a clue about using the proper materials on an old house.

    Your local council's conservation officer will probably be able to recommend someone for this.
     
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  13. Alicegal

    Alicegal Member

    Hi, so we have moved on a wee bit from the last post. I have now removed most of the plaster (lime mostly) from the wall that suffered from condensation. In doing so, I discovered a fairly significant crack in the bottom left corner of the wall. Panic!! The wall is solid sandstone and upstairs. Is this crack a serious sign of settlement or subsidence? Should I be running for the hills? I'm stressing out here. The idea was to build an internal stud wall, leaving a small cavity behind it. We will then put celotex insulated plasterboard onto the stud wall to bridge the thermal gap. I'm just very concerned about this crack. It looks as though it has been filled in the past. The crack (if the fillings were to be removed), is fairly wide! See photos. The adjoining lime plastered wall on the left side is an outside wall. Thanks guys!
     

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  14. koolpc

    koolpc Well-Known Member

    Doesnt look dangerous to me. Its an old house? So expect these things. If worried, get a Structural Engineer to take a look or a surveyor.
     
  15. Joe the Plumber

    Joe the Plumber Active Member

    It's hard to be sure, but given your house is old, I agree with Koolpc. The crack's probably ancient and if it's not fallen down by now, it's not going to.
    Does it also appear outside?

    You could get a structural engineer in to have a look to be certain. I wouldn't bother with a surveyor though (they'll simply recommend you get the
    structural engineer in!)
     
  16. Mr Rusty

    Mr Rusty Well-Known Member

    From a non professional perspective, I also don't think this is anything to worry about too much. Old houses often did not have deep foundations, and were built with lime mortar. Inevitably houses moved about slightly as ground gets dry/becomes wet and the soft mortars allow it to move. Subsidence IMHO is when it moves in a way from which it can't recover. Also, over time structural timbers will also move.
     
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  17. Alicegal

    Alicegal Member

    Thanks so much guys. Ok, next panic attack ... (sorry for driving you mad - it's turning out to be a bit of a saga here!). We found thin sheets of what my husband thinks could be asbestos - around the edge of the room, under the skirting, stuck to the wooden laths as you can see in the photos. He thought it was asbestos due to the bumpy pattern on it and tiny hairs inside? Any ideas?
     
  18. Mr Rusty

    Mr Rusty Well-Known Member

    No more pictures?
     
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  19. Alicegal

    Alicegal Member

    Sorry, photos below!
     

    Attached Files:

  20. Mr Rusty

    Mr Rusty Well-Known Member

    Doesn't look like asbestos to me - they used a lot of horsehair in lime plaster, looks like that. Very similar to what I have seen on my project. what do others think?
     
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