Damp spot in fresh plaster - update

edited 8 December 2022 at 5:38PM in In my home (includes DIY) MoneySaving
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NoisyGiraffeNoisyGiraffe Forumite
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We had our front room skimmed 6 weeks ago, most of the room dried nice and quickly but there's one patch that still hasn't dried out. It's on one side of the bay window at the top, only covering the two windows on the left.





When we moved in 2 years ago there was damp around the bottom of the bay. We had the cavity cleared and the plaster was knocked off, bonded and then left like that until the room was just skimmed. The wallpaper in the upstairs bay is peeling and I'm suspecting the cavity between the windows may also be blocked. I might be way off here so please let me know if you have any pointers! The windows have all been re-siliconed, the gutters replaced and fascias capped, the whole house has been repointed, so I can't think of any other sources of damp there except the cavity.

The radiator is still off the wall in this room because we didn't want to faff putting it back on to take it off again to paint. But the door to the rest of the house is kept open and when it isn't damp and rainy outside I open the window to get some ventilation.

I'm not sure if this is the right plan but I'd like to try and dry it out, and if we can get it dry, wait to see if any dampness reappears to confirm there is a problem. Does that seem right? What would we use to dry it - a normal cold fan? A heated fan? 

If the cavity is blocked, can be fixed from the room above rather than hacking this plaster off and redoing it?

Thanks in advance! 
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  • twelvegoldbarstwelvegoldbars Forumite
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    builder here..,you say the walls were bonded before plastering?,if carlite bonding has been used then this should not be used on an external interior wall,as its hydroscopic and contains vermiculite and will seek out moisture much like a sponge,have you had the felt ends checked on your roof? as these can rot and cause water to ingress,regaurdless if you have had new fasia and guttering
  • NoisyGiraffeNoisyGiraffe Forumite
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    Thanks @twelvegoldbars

    Not sure what was used! But there hasn't been any more problems at the bottom where that work was done, it all seems to have dried out fully.

    We haven't had any work done to the roof on the bay. The roofer that did the fascias and gutters did say that it looked fairly new and in good condition, but I'll bear this in mind. 

    Would you know whether it'd be possible to clear the cavity from the room above? And the best way to dry out the plaster in the meantime to see if the damp returns?
  • twelvegoldbarstwelvegoldbars Forumite
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    carlite bonding does take an age too dry, especially if it has been reskimmed the same day  and also depends on the thickness of the bonding,get some heat in the room and see how it gets on if it comes back wet again after drying ,then something is amiss ,any form of blown in  cavity insulation is a NO NO ,the cavity is there for a reason..,insulation should be applied INTERNALLY and not externally with 75mm celotex and plasterboard ,avoid external insulation, or spray foam in the roof structure,to clear the cavity of blown insulation would need too be vaccumed out,there are companies that do this..also check your drip vents on any pvc windows for debris as water can find its way into the walls, especially if they have fixings through the pvc cills 
  • diystarter7diystarter7 Forumite
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    Hi OP

    Silly question. But did it dry out completely and if not, my guess is that its cooler there and weather is dampy and the plaster may be thicker so taking longer to dry?

    I'm sure the helpful builder will put me straight

    Good luck
     ..

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  • NoisyGiraffeNoisyGiraffe Forumite
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    Hi OP

    Silly question. But did it dry out completely and if not, my guess is that its cooler there and weather is dampy and the plaster may be thicker so taking longer to dry?

    I'm sure the helpful builder will put me straight

    Good luck
    Not a silly question! No, it's never dried out there. Some days it looks like it's dried a bit more, others I think it looks darker again. There was no bonding behind this bit, just skimmed onto the original plaster so shouldn't be too thick. But that side of the bay does get more weather so it probably is naturally colder and get more wet. 
  • FreeBearFreeBear Forumite
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    Got a photo of the outside of the bay where this patch of damp plaster is ?
    Preferably, one that provides context rather than a tight close up shot.
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  • NoisyGiraffeNoisyGiraffe Forumite
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    @twelvegoldbarsThanks, going to get some heat in there today and see how it goes. 

    Not a fan of cavity wall insulation but it had already been put in years ago before we bought the house. It's the wool type. Full removal would have to be a future job, but fortunately no signs of any problems anywhere else in the house, just under these bay windows and I think this could be caused by sand from the sandstone mullions (which are still standing but quite a bit of deterioration in some places - some will need replacing in future when we have the money). 

    I haven't checked the drip vents on the upstairs windows yet so I'll do that today - thank you! 
  • diystarter7diystarter7 Forumite
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    Hi OP

    Silly question. But did it dry out completely and if not, my guess is that its cooler there and weather is dampy and the plaster may be thicker so taking longer to dry?

    I'm sure the helpful builder will put me straight

    Good luck
    Not a silly question! No, it's never dried out there. Some days it looks like it's dried a bit more, others I think it looks darker again. There was no bonding behind this bit, just skimmed onto the original plaster so shouldn't be too thick. But that side of the bay does get more weather so it probably is naturally colder and get more wet. 
    Thanks. Then I'm hoping its still wet but as another said, check the outside frame, sides and top. If you have flashing there check that as well and a bit of water could be coming through the tiles on the bay if you have them

    If there is no sign of  leaks it may just be drying but if it looks drying and next day there appears to be more, then in my DiY expereince there may be a seepage outside

    Was there any evidence whatsoever, even a tiny doubt before the replaster re any dampt patch?

    BTW - where the windows recently installed ie 12 months or so ago?
     ..

    Before you spend, remember the 
    MSE Money Mantras. Ask yourself, do I need it? Can I afford it? If the answer is NO to any of those questions, DON’T buy it.  (Quote from MSE  15/11/22)


    Politeness & courtesy are some of the few things in life that are free. Please remember that when posting, I may ignore permanently the unpolite, tedious, unconstructive and deliberately obtuse comments. Many thanks.
  • NoisyGiraffeNoisyGiraffe Forumite
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    Hi OP

    Silly question. But did it dry out completely and if not, my guess is that its cooler there and weather is dampy and the plaster may be thicker so taking longer to dry?

    I'm sure the helpful builder will put me straight

    Good luck
    Not a silly question! No, it's never dried out there. Some days it looks like it's dried a bit more, others I think it looks darker again. There was no bonding behind this bit, just skimmed onto the original plaster so shouldn't be too thick. But that side of the bay does get more weather so it probably is naturally colder and get more wet. 
    Thanks. Then I'm hoping its still wet but as another said, check the outside frame, sides and top. If you have flashing there check that as well and a bit of water could be coming through the tiles on the bay if you have them

    If there is no sign of  leaks it may just be drying but if it looks drying and next day there appears to be more, then in my DiY expereince there may be a seepage outside

    Was there any evidence whatsoever, even a tiny doubt before the replaster re any dampt patch?

    BTW - where the windows recently installed ie 12 months or so ago?
    No we didn't think we had any problems above the window before the plastering was done, but you've got me thinking now! The room has been stripped for 2.5 years, that's when we had the bottom cavity cleared, so it's just been bare plaster all this time and no evidence of there being a problem. But I just went back to look at photos from when we viewed the house and can see that the wallpaper above the window was also peeling away. I guess we didn't know enough at that point to consider whether there was a damp problem there aswell. Being a first time home owner is a steep learning curve!! 

    We're just about to put some heat in there so hopefully we can dry it out, and see if any damp comes back when it rains and if it does then hopefully we'll be able to pinpoint where the issue is. Thanks for all the pointers.

    Windows at the front were installed quite a while ago - I think around 2005.
  • diystarter7diystarter7 Forumite
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    Hi OP

    IMO, if it keeps on coming back then I do feel you may have a problem as posted earlier.



    These type of windows often attract minor  movement/cracks at corners it could be that or flashing/sealant needs looking at.

    Re windows, ok but the sealant can and does degrade and it also happens to poorly finished newer windows - see how it goes and possbily take a couple of pics inside or mark the patch see if it decreases and if it then reappears.

    Hopefully, its drying out but as you said in op if its coming back, then possible leak that you guys should be able to resolve.

    Good luck
     ..

    Before you spend, remember the 
    MSE Money Mantras. Ask yourself, do I need it? Can I afford it? If the answer is NO to any of those questions, DON’T buy it.  (Quote from MSE  15/11/22)


    Politeness & courtesy are some of the few things in life that are free. Please remember that when posting, I may ignore permanently the unpolite, tedious, unconstructive and deliberately obtuse comments. Many thanks.
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