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Damp patch underneath window sill (pics inside)

Discussion in 'Building' started by martin645, 30 Nov 2012.

  1. martin645

    martin645

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    Hi all,

    I'm looking for thoughts on a damp patch that has recently appeared underneath the window sill in my bedroom.

    Wide shot of the whole window bay:
    [​IMG]

    Shot of the corner of the window showing the weather seals:
    [​IMG]

    Looking down the outer bit of the open window - inside on the left, outside on the right:
    [​IMG]

    The window is a modern-ish double glazed affair, the outer wall is old stone. The damp patch is entirely confined to the underneath of the interior window sill, and has a weird, "patchy" distribution - some bits are very damp and some bits not at all. The damp bits show up as darker patches on the photos.

    The patch has been very slightly damp for a while now, but has suddenly got much worse in the last two days. We haven't had any rain at all in the last couple of days, but we have had two very cold nights, which makes me wonder if the dampness could be due to condensation on the inside of the window, dripping down somehow and emerging underneath the sill. There is a fair amount of condensation on the glass on the inside of the window, especially near the edges (you can easily see it on the full-sized version of the first photo). Two humans and four dogs sleep in this (quite small) bedroom overnight, plus we often have washing drying on the radiator, so there is plenty of scope for there to be a lot of moisture in the air.

    Other potentially relevant information: the weather seals on the window are not in great condition, and there is a hole (around 1/2 inch diameter) drilled through from the outside at just above ground level that used to be filled by a cable from a satellite TV dish.

    I will go out tomorrow during the day and get some more pictures from the outside - please say if there's anything you want to see. I have uploaded full-resolution pictures, so you should be able to zoom in for more detail. Please excuse the dirty condition of the window and sill! I am pretty inexperienced with this kind of thing so if there's any important information I've missed out, please ask.

    Thanks in advance for any advice,

    Martin
     
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  3. Aqua

    Aqua

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    Is the window sill wet? Does moisture drip off it and onto the lower wall?

    Is the effected area wall papered?

    If you dont have damp getting onto the wall in a way you can trace i'd suspect cold bridging, especially as you say it has got worse in cold but not wet weather. Woody will probably have a better idea then me if he looks in here.

    You probably need to ventilate the room better, the amount of condensation on the window tells a tale. You say two humans and 4 dogs sleep in the room, could the dogs sleep elsewhere? Do you have the bedroom door closed at night? Maybe think about a dehumidifier to bring the condensation under control.
     
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  4. martin645

    martin645

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    Aqua,

    thanks for the reply. The (inside) window sill is dry everywhere that I can touch it, which makes me think that if the dampness is due to condensation, then it must be running down the window and somehow getting underneath the sill. The affected area is papered.

    Good idea re. ventilation and dehumidifier - I might run out and see if I can pick one up this weekend and see if that helps matters.

    cheers,
    Martin
     
  5. Aqua

    Aqua

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    If condensation was dripping off the window and down i suspect you would be able to follow the course of it past the bottom of the window and onto the window edge of the sill.

    I don't think that's the problem. As the wall is papered i suspect if the issue is cold bridging, condensation forms behind the wall paper causing the damp areas which show in the photos.

    Is the wallpaper lifting in those areas, does it feel/look like it would come away easily?
     
  6. joe-90

    joe-90

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    Looks more like a leak down the cavity to me.
     
  7. noseall

    noseall

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    Looks to me like there is no cavity.

    Reading the op's post points towards cold bridge condensation damp - i.e. zero rain, cold temperatures outside etc.

    Also, if this is an occupied bedroom then the possibility that someone has been breathing out moist air for 8 hours would compound the issue.
     
  8. joe-90

    joe-90

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    How thick is that wall? Looks way too thick to be a cold issue, and why does it seem to be only at the sides of the window? It looks like there is a section in the middle that has been removed in the past? If not, what is that line? Is it a solid wall below? Or lath and plaster?
     
  9. martin645

    martin645

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    Thanks for all the replies,

    The paper is not exactly lifting away, but it is a little bit flaky - i.e. I can pull it away without too much effort.

    Some additional info: I left the door open overnight for ventilation and most of the moisture has cleared - the wallpaper still feels a little bit damp but there are no drips running down the wall like there were last night. Also, I measured the temperature of the walls with an IR thermometer: the other walls at the same height are 16 degrees but the bits where the damp has gathered is around 11/12 degrees. So I could well believe that overnight those bits of the walls easily get cold enough to cause condensation out of the air.

    joe-90: It's a bay window; the thickness between the interior and exterior wall is about 13 inches in the bay where the window is, and about double that elsewhere. The damp does seem to be worse at the sides; I have no idea why this is! The horizontal line near the floor is just a join in the wallpaper. I think it's a hollow wall - it sounds hollow when I tap it.

    Thanks for putting up with my inexpert descriptions!
     
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  11. HERTS P&D

    HERTS P&D

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    Does the external stone cill have a drip underneath? If not you can cut one with an angle grinder.

    Andy
     
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  12. martin645

    martin645

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    Andy,

    By a drip, you mean a groove running underneath the cill that stops water running along the underside of the cill to get to the wall, right?
     
  13. joe-90

    joe-90

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    Yes, a capillary groove - and a good call from Andy.
     
  14. Aqua

    Aqua

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    Still sounds like cold bridging to me (sorry joe-90).

    I know there are still quite a few who dispute the existance of cold bridging being the cause of mould and damp on internal walls but just two days ago i removed external bricks to reveal a cavity bridge, the other side of which was damp/mouldy yet the cavity and bridge where snuff dry..

    The OP says he has changed a few life style habits and results are instant.

    Remove the sleeping dogs from the room, leave the bedroom door open at night, ventilate as well as possible (cold weather i know), dehumidify if necessary and things should get better.
     
  15. noseall

    noseall

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    They would have to be idiots then!

    Funny how this materialises when the weather is BONE DRY and VERY COLD outside.

    Cold bridging has never been in doubt. Its signature tell tale signs are revealed whenever the weather turns cold, in spotting and shadowing etc.

    The problem is people look for everything but cold bridging, when damp manifests itself and scratch their heads wondering how it can be happening when it is dry outside.

    That's because the moisture is coming from INSIDE!
     
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  16. joe-90

    joe-90

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    That's not cold bridging - that is condensation.
     
  17. noseall

    noseall

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    What is?

    Or isn't?
     
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