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  1.  
    Asked by a relative for advice on this but not sure if there's really much useful to suggest.

    It's a sandstone walled outhouse, once upon a time a stables. Stone floor straight on the ground. The roof seems sound, I don't think leaks are the problem.

    It's perennially damp inside especially in the winter. Put a bicycle in there and it starts to go risty. Maybe some of this comes from the ground. But they report often seeing condensation on the inside of the walls. It's not heated or normally occupied.

    Some of the sandstone walls have been partially rendered with cement. Obvious advice might be to get this off so that they can at least dry off towards the outside. But I'm not sure whether it's likely that would make enough difference.

    Not much point suggesting extra ventilation, I don't think. The air inside is effectively 'outside' air; there's a big leaky stable door. My impression is that the condensation occurs even when there are not any moisture-generating humans in there.

    So the question really is whether there's anything to suggest to improve things - or is it simply that an unheated outhouse in this location is always going to be damp.
  2.  
    The most effective ventilation is cross flow - so whilst there is a leaky door is there another vent hole somewhere to provide cross flow?

    Are stored items put in there wet?

    I would be surprised if removing the partial render would make any difference.
  3.  
    Hack off all render inside and outside then rake out and repoint the walls with lime mortar and the damp will disappear. Stable blocks where designed to breath and remain dry even with sweaty horses in them.
    • CommentAuthortony
    • CommentTime3 days ago
     
    +1
    • CommentAuthorIan1961
    • CommentTime3 days ago
     
    It's possible that the condensation is caused by salt damp. Salts (from animal urine) are hygroscopic and can be the cause of damp problems in barns & stables.
  4.  
    My garage was damp until I sealed under the bottom of the doors with a rubber strip. Seems that most of the dampness was coming from rain running down the doors and then blown in by the wind. It was not from rising damp as I had suspected. I did not seal round the top of the doors and that's enough ventilation to keep it dry.
  5.  
    Posted By: renewablejohnHack off all render inside and outside then rake out and repoint the walls with lime mortar and the damp will disappear. Stable blocks where designed to breath and remain dry even with sweaty horses in them.


    The wall's not rendered on the inside as far as I recall.

    It seems to me that if damp on the inner part of the wall can move out sufficiently fast by migrating through thick sandstone/lime mortar walls - then surely it ought also to be able to dissipate simply by evaporation from the internal surface, which is essentially connected to the outside air via the large, leaky door.

    Of course if the real cause is rainwater getting into the body of the wall then I can see that removing the outside render/repointing could make a difference.

    Regarding cross-ventilation; they tell me that they hear the wind whistling through the tiles/sarking boards which led me to assume that there was effectively ventilation through a non-airtight roof. But I wonder if I should suggest introducing a couple of deliberate vents on the opposite side from the door.
  6.  
    Your relatives mentioned condensation on the inside of the walls. That means water in the air is being transferred to the wall, not the other way around. IE the 'ventilation' air is too damp and is part of the cause of the problem, not the solution.

    Sounds like something is making the interior air damp, either a water leak in through the roof walls or floor, or rain/mist/snow blowing in through the doors.

    Can you go stand inside it during heavy rain and see what's going on?

    Maybe obvious but all 'ventilation' openings need to be rain-screened with a louvre or similar, a big open gap will just let in rain. If the wind can blow in between the tiles it will blow rain in with it.
  7.  
    Posted By: WillInAberdeenYour relatives mentioned condensation on the inside of the walls. That means water in the air is being transferred to the wall, not the other way around. IE the 'ventilation' air is too damp and is part of the cause of the problem, not the solution.

    Sounds like something is making the interior air damp, either a water leak in through the roof walls or floor, or rain/mist/snow blowing in through the doors.

    Can you go stand inside it during heavy rain and see what's going on?

    Maybe obvious but all 'ventilation' openings need to be rain-screened with a louvre or similar, a big open gap will just let in rain. If the wind can blow in between the tiles it will blow rain in with it.


    Yes it's the condensation on the inside of the walls that seems significant to me. My thinking was that it's the same kind of condensation that you might get outside, ie. dew, in certain conditions, but it wasn't able to dry out quickly enough. But you're right that it does seem to suggest that something additionally is making the internal air damp.

    It's not something I can look at in person for a couple of months. But might ask them a couple more questions based on the comments on this thread.
    • CommentAuthorSilky
    • CommentTime2 days ago
     
    don't forget that even an unheated building will warm up from the sun, significantly if there is not insulation (what type of roof covering)? Therefore maybe this warmer air holds more water which then condenses due to night cooling and seasonal changes. I've visited a similar property (sandstone with the exterior 'protected from the weather' ) and seen sandstone on the inside that was almost dripping with water, stones falling apart and the walls collapsing.. and that was a building that had stood for 700 years until it was modernised in the 20th century (my presumption). So I think you really have to get the render off the outside, it's a well known problem. In the meantime just leave some windows open, cold is not always the problem, the older part of my house has not been heated for 8 years and is totally dry, it has very old lime render or bare stones on the outside.
  8.  
    Posted By: lineweight
    Posted By: renewablejohnHack off all render inside and outside then rake out and repoint the walls with lime mortar and the damp will disappear. Stable blocks where designed to breath and remain dry even with sweaty horses in them.


    The wall's not rendered on the inside as far as I recall.

    It seems to me that if damp on the inner part of the wall can move out sufficiently fast by migrating through thick sandstone/lime mortar walls - then surely it ought also to be able to dissipate simply by evaporation from the internal surface, which is essentially connected to the outside air via the large, leaky door.

    Of course if the real cause is rainwater getting into the body of the wall then I can see that removing the outside render/repointing could make a difference.

    Regarding cross-ventilation; they tell me that they hear the wind whistling through the tiles/sarking boards which led me to assume that there was effectively ventilation through a non-airtight roof. But I wonder if I should suggest introducing a couple of deliberate vents on the opposite side from the door.


    Your first comment said it was cement rendered.
  9.  
    Posted By: lineweightSome of the sandstone walls have been partially rendered with cement.

    From the first post, by this I had assumed that there was not much render
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