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Small damp patches in plaster

Discussion in 'Plastering and Rendering' started by Coniferman, 3 Jan 2016.

  1. Hi,

    I have recently been scrapping off the paint in a downstairs room. The paint wasn't particularly bad but there was a little bit of flaking and crazy-paving affect and a small number of hairline cracks so I decided rather than paint over to go back to plaster. (The paint was no worse on external or internal walls)

    Last night was very wet and windy and now I have noticed 4 small circles in the plaster that are clearly damp due to a dark colour. They are between about 1.5 and 2 meters off the floor and between 4 and 8 cm in diameter. They are all on the wind facing side of the house, external wall.

    The room is not heated much - about 16C and 60% relative humidity.

    Obviously the damp patches will soon dry but can I assume this is something that needs immediate attention? The wall is 1980's Brick and Block and the cavity filled a few years ago. The external wall (just on that side) the mortar has taken the affect of the weather although I'm not sure if it requires repointing just yet. It is a gable end so there is no gutter. The roof verge (correct term?) is just concrete. (not wood like some houses) I have noticed what looks like there might be a small crack in the plaster near the very top of the roof.

    Any thoughts on likely cause? I assume it is more than just needing the heating on higher?

    Thanks.
     
  2. roy c

    roy c

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    Pics !!!
     
  3. [​IMG]

    The line around the top, isn't a crack or anything. The plaster isn't blown. Just where it is drying, I guess. The plaster is more brown colour than it looks in photo.
     
  4. roy c

    roy c

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    It looks like you have "dot and dabbed " plaster board on your walls. This is plaster board that is stuck on with "Dabs" of adhesive . If the dots are showing through then you must check your outside wall for cracks or any where that water could be getting thru. A cavity wall is supposed to keep water from tracking from outside to inside that what the cavity does. But it seems as though the cavity is being "bridged " and damp is showing through on the dabs. I personally don't like filled cavities but there may be another way the water is bridging. On a dry day (I know!!!) if we get one, get an hose pipe and start at your dpc line and spray water on the wall and get your missus to stay inside by the wall and give you a shout if she notices if any damp marks appear. Now don't rush it ,take it easy and work up the wall slowly and see what happens. The damp may not appear and if it doesn't then it may be coming from the roof or some where else. Just take it easy and methodical and you might get your answer.
     
  5. Thanks for reply. Sorry- should have mentioned it is NOT plasterboard. It is brick, block and plaster. At least I think it is some sort of plaster?? It is VERY thin covering (not even 1mm !!) over what looks like grey block. Isn't plaster thicker than this?? Don't know what else it could be?

    Anyway it is NOT plasterboard. I just checked the external brick and found one hole that I could get a 4mm diameter tool in, at least 4 inches and a couple of other areas where a medium cable tie would go in. These have now been filled. I'll get the ladders out during the week to check higher up. Could this have caused it?????? Just seems odd that they are such small round patches.

    P.S. looking at the garden, the weather must have been exceptionally bad overnight.

    Noted the suggestion with the hosepipe.
     
  6. Ignore what I am saying about less than 1mm of plaster on block. I'm not sure what it is. It is a course brown/grey brick type substance with a very thin hard finish to it. Different to what I am used to with filling plaster. Certainly not plasterboard anyway.
     
  7. joe-90

    joe-90

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    My personal view is that due to the very clear definition of the spots, I'd suspect water getting down the cavity from above and hitting wall ties and running into and through the wall.
     
  8. Thanks for the replies. I'll check the roof and external wall again in the daytime. Local news reporting mayhem this morning due to torrential flash downpours. Maybe I was just lucky/unlucky to have gone back to plaster at this time. In the meantime, it has more or less dried out encouraged by some gentle heating from a hairdryer. Won't rush to repaint, so I can monitor it. A couple of other houses in the road have had the one wall facing the weather, re-pointed recently, so maybe bring that forward.
     
  9. Looks like there are probably more small holes in the pointing, higher up than I want to go with a ladder so looking at getting the whole wall re-pointed. Presumably this could well be the cause of the damp? Particularly with driving rain. Whilst I'm at it, anyone know if this crack in the roof verge is a major problem? The picture isn't actually of the roof but the roof has a similar crack just a bit further down from the top. Maybe they can re-point that whilst they are at it??

    [​IMG]
     
  10. chris_o

    chris_o

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    I wouldn't get the whole re pointed straight away. You've said the pointing isn't that bad, and it could be a complete waste of money getting it re pointed at this stage. If you've got similar cracking to the roof mortar above, get that sorted first and go from there
     
  11. Just spoke to neighbour who turns out had the same problem and had the roof mortar replaced and the pointing fixed as necessary. As you said, not a complete re-point. Thanks.
     
  12. joe-90

    joe-90

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    I've been in the business for 35 years and never seen a house that leaks from the side due to the weather. It's always the top.
     
    • Thanks Thanks x 1
  13. Had a quote to remove the first two sets of tiles, fit new felt, replace soffit strip mortar, replace tiles and repoint the top section of brick and paint water seal the brick. One gable end only. £4000. Does that sound about right?
     
    Last edited by a moderator: 7 Jan 2016
  14. joe-90

    joe-90

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    Only if you called a caravan dweller. £500 tops. Maybe if it's difficult to reach a bit more for access.
     
  15. :D I am down $outh though!

    First quote included scaffolding. Had someone else out who can just fill the cracks straight away and fill any brick mortar holes and spray seal (porous brick) from a ladder. Needless to say this costs considerably less.
     
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