Damp/mould spots on living room walls - help!

[Vicky Willimott]

Please see attached pictures. We have now got little damp spots all over one wall in our living room and now noticing it on other walls. They are small little spots about 5mm-10mm across. Room was replastered last year. First noticed spots a few months ago and has got increasingly worse since - anyone got any ideas what it is, what's causing it, any products I could use to "clean" the spots? Probably also worth noting we are extending the house at the moment (spots started before this), currently have no boiler/heating, and getting condensation on windows. Any help much appreciated! Thank you

 

[Doug99]

Open the windows and vent the room, condensation is caused by moist air settling on cold surfaces. Lack of heating will not help the situation so remove the cause ie dont dry wet clothes indoors. A bedroom ceiling can get mouldy purely from the breathing of sleeping occupants if windows are closed.

 

[JP_]

would those be condensation caused though? Are all these on the same external wall? Or all over? I thought condensation mould tended to be more patchy, in corners and lower on the wall?

 

[Vicky Willimott]

They are all over one internal wall (which is the dividing wall of our house and neighbours) and have started on the window wall now too. My first thought was possibly condensation but I really have no clue. It's all over the wall up to about 5 foot ish but has been getting progressively higher since the problem started

 

[JP_]

I am certainly no expert, but i do have my own mould problems from condensation and this looks very different. My guess is that this could be the wall behind is wet and the moisture is getting through by the dot and dab blobs that hold the plasterboard to the wall. But, we need more opinions!

 

[JP_]

https://www.diynot.com/diy/threads/dot-and-dab-cold-spot-damp.475031/

Could it be cold spots from dot and dab?

 

[Vicky Willimott]

I'm really not sure they're very small spots. Have however just looked behind sofa and sofa has blue/green mould spores on? And appears to now be some black mould spores appearing on plastic around windows

 

[JohnD]

getting condensation on windows

is the house excessively humid, for example due to new plaster, leaking roof, or wet washing draped indoors?

When do you open the windows?

Have you got a water meter?

the spots of damp are too numerous to be dot-and-dab bridging.

 

[Vicky Willimott]

Have had some washing indoors at times, as not able to get to garden at the moment due to building work going on. I have windows open during the days I am at home (usually 9am til about 3/4pm at least 5 days a week). We had the living room replastered last year and the hallway/landing was done at the beginning of this year (adjacent to the living room)
We have got a water meter

 

[JP_]

if there is mould growing on the sofa, must be very humid inside, as it's not really started getting cold yet.
Do you have extractor fans in kitchen and shower rooms? What building work is being done? Could this be affecting it in any way? Could some air vents have been blocked up?

 

[Vicky Willimott]

We do have an extractor fan in bathroom but if I'm honest I'm not convinced it works properly. No damp issues upstairs (touch wood) that we've noticed yet.
Currently we have a temporary kitchen rigged up in a hallway (our old kitchen got knocked down and we are currently doing a two storey extension to side of house). No extractor fan in temporary kitchen area but I have been trying to have windows open whilst cooking etc to keep it as ventilated as possible.

 

[IWalkLikeHimaMartian]

... currently have no boiler/heating, and getting condensation on windows. ...

Without heating, even with sufficient ventilation, your internal RH will be exactly the same as outside, or maybe higher due to lifestyle. External air is often over 80% RH. Although today it is low (about 60%) possibly something to do with the high winds or warm air brought by the high winds..

The way to reduce internal RH is to let in cold air with a high RH (you cannot control the RH of the external air coming in). Then heat that air, allowing the RH to fall. The air can then absorb more moisture, raising the RH again. This warm air, with a now high RH, is allowed to ventilate to outside, taking the additional moisture with it. The cycle is repeated ad infinitum, eventually reducing the internal RH. Bearing in mind that while you have a high internal RH, the building fabric will also absorb additional moisture. You will need to maintain a consistently lower RH, for a period of time, for this moisture to be released from the building fabric, absorbed into the air and ventilated to outside.
But without heating, any attempt at ventilation is almost pointless.
In which case a dehumidifier is required. But then ventilation is explicitly not required, otherwise you are trying to dehumidify the rest of the world.

 

[Vicky Willimott]

Ok that makes some sense. Will have a look at a dehumidifier. Thank you

 

[anobium]

Google "dew point" and that will tell where condensation comes from, at the end of the day there are 3 ways to eliminate condensation, insulate,ventilate, or increase the heat.
If the condensation is due to some self induced reason, for example drying clothes inside , wet trades plastering taking place, then the answer is obvious .

 

[JP_]

Venitlate - problem is, if its damp, this won't work will it? If you leave fabrics outseide under cover, it will still get mouldy. We had to leave a dining chair outside under a sehlter for most of September, and it was already showing signs of mould on the cushion. Rain did not get to it. Could not have been more ventilated unless it was in a wind tunnel!