I had this problem last winter, cleaned off using strong bleach solution around March time, came back around end of November.
The damp problem seems to be limited to the bell cast area of ceiling, you can see damp free areas where wooden joists attach to inner ceiling. I have been told I have insulation in my loft but have not looked as the loft hatch is tiny, and I am not lol.
I am not sure if the bell casts are insulated though, as I have been told by a builder that came to price up a floor said that they would not be as the house is old (thick stone outer walls)
I have double glazed windows, although they do not have any trickle vents. they can lock slightly ajar.
any ideas as cause to damp/mould and any remidies I could try.
Could the shower be to blame? window is opened most time it is used, cant see this though as small bedroom directly opposite has no damp issues only rooms to left of bathroom and hall roof outside to right.
I think there is no insulation in that area,hot air is rising and condensating on the ceiling causing mould. Removal of the contaminated plasterboard is needed.And replace with new or use T&G pine for a better finish.Call your insurance assessor they may foot the bill.
You do not need to remove the plasterboard or insulate the area. Increase the internal ventilation to decrease relative humidity within the property. Once this has been carried out, use a fungicidal spray (available from most DIY shops, but normal house bleach does pretty much the same thing.) and spray affected area. Once all is done, repaint as necessary.
Internal relative humidity levels should not be allowed to raise above 60%, if this is the case, condensation will occur causing the mould growth as experienced. If you cannot afford to increase the ventilation by way of installing air bricks or extractor fans, open a window when you are at home and get some fresh air in there.
During the winter months, I get around 20 calls per week asking me to diagnose this kind of problem when the quickest, cheapest and easiest remedy is to open a window ;)
Steve, I understand your point but Mycotoxins are a problem in large mould growths and rarely in areas such as these, also as you know the species of mould dictates the type and amount of Mycotoxins excreted. There is a lot of conflicting information available about this subject and one has to be unbiased in their approach. You could have a mouldy sandwich that produces mycotoxins but that doesn't mean that it will produce anywhere near the amounts needed to cause any ill effects to health unless there was already a serious underlying health condition such as respiratory or allergic.
You state that relative humidity levels of 50% can cause condensation on cold surfaces. I totally agree, you could even have a 35-40% RH and cause condensation dependant on the temperature of the condensing surface. It all comes down to dew points and the temperature of the surface. I say 60% as a general rule of thumb unless of course you are living in the arctic with external temperatures reaching -20 where it would obviously have different variables.
You will find a lot of companies actively selling a product to combat mould that will hype the detrimental health effects of "Toxic moulds" but the truth is, there is not enough evidence to give a concise answer to many of the myths.
The majority of DIY mould killers contain chlorine as an active ingredient and it is chlorine (bleach) that I recommend my customers to use to remove the fungal growths due to condensation. Spraying the mould will bleach will not cause it to release its mycotoxins as they are (if evident) released as part of the cycle of that particular fungus.
The substrate that the mould is growing onto as well as local environmental conditions hugely dictate the methods and products used to contain or kill fungal growths but within the scope of the original question, I do believe and can prove that chlorine based products eradicate these surface moulds and that increasing ventilation within the property reduces the re-occurrence.
I would also like to point out that the spraying of these chemicals should be carried in accordance with manufacturers instructions and it would be extremely fool hardy to be spraying any form of chemical in the presence of an adult let alone a baby. The re-housing of the baby would only be carried out into the affected area once the area has been fully dried out and ventilated. If you wanted to deep clean a room before putting a baby in there, I would use bleach every time to disinfect that area and take exactly the same steps before introducing a baby into that environment.
I do understand your points and they are taken with thanks but there is a lot more to it that isn't fully understood with a lot of hype and scaremongering. In instances such as described and shown by the original poster, I would continue to use my conventional methods until such a time where more evidence is available.