spots/mould on the solid wall!

stuart45

It's best the check the temperature and relative humidity of the room first.
Also worth getting a surface thermometer to check the temperature of the external wall. This will point out any surface where condensation is forming.

Section62

sujsuj said:

stuart45 said:

You would expect a 20 year old extension to be a cavity wall, although you can never be sure, especially in rural areas. It's quite common where I live for people to build extensions without permission, and farmers building bungalows for their kids.

This is what I can see from inside under sink. This is just inside big bush you see in the photo (you can see waste pipe). So I suppose this is part of cavity insulation done previously.

More likely to just be expanding foam someone has used to seal round the pipes having made holes in the wall/floor for them to come through.

One if the issues when extending is that a previously external wall can become an internal one.  In some situations this provides a cold/damp bridge from the remaining external wall(s) into what is now an internal wall.  This is a detail the architect/builder ought to take into account to minimise the risk of problems.

In your case with solid walls it is slightly less critical, but might explain why two walls in the same room are showing signs of damp/mould.  I.e. the wholly external wall, and another wall which is connected/integral to the external wall, but now functions as in internal one.

stuart45

Section62 said:

sujsuj said:

stuart45 said:

You would expect a 20 year old extension to be a cavity wall, although you can never be sure, especially in rural areas. It's quite common where I live for people to build extensions without permission, and farmers building bungalows for their kids.

This is what I can see from inside under sink. This is just inside big bush you see in the photo (you can see waste pipe). So I suppose this is part of cavity insulation done previously.

One if the issues when extending is that a previously external wall can become an internal one.  In some situations this provides a cold/damp bridge from the remaining external wall(s) into what is now an internal wall.  This is a detail the architect/builder ought to take into account to minimise the risk of problems.

That's a good.point. When a cavity wall is built against a solid wall there is a slight weakness at the join because moisture can get through a 4 inch skin relatively quickly.

Section62

stuart45 said:

Section62 said:

sujsuj said:

stuart45 said:

You would expect a 20 year old extension to be a cavity wall, although you can never be sure, especially in rural areas. It's quite common where I live for people to build extensions without permission, and farmers building bungalows for their kids.

This is what I can see from inside under sink. This is just inside big bush you see in the photo (you can see waste pipe). So I suppose this is part of cavity insulation done previously.

One if the issues when extending is that a previously external wall can become an internal one.  In some situations this provides a cold/damp bridge from the remaining external wall(s) into what is now an internal wall.  This is a detail the architect/builder ought to take into account to minimise the risk of problems.

That's a good.point. When a cavity wall is built against a solid wall there is a slight weakness at the join because moisture can get through a 4 inch skin relatively quickly.

And if the junction is slap bang where a leaking gutter is pouring water out then some moisture penetration shouldn't be a surprise.

ThisIsWeird

sujsuj said:

I am seriously considering dehumidifier..I  wasn't sure it it will cause any health issues..?

Don't panic - these spots are mild by any mouldy standard. Once you've sorted the cause - and let's hope you have - it won't get any worse. And it looks as tho' you've got rid of the actual spots anyway.

Yes, mould can be a health issue, but unless you are very vulnerable, it would need to be pretty bad, and you'd have to be living in that room for a good part of the time.

What's that room used for? If it's a current bedroom, then just ventilate it during the day - flinging the windows wide open on dry sunny days - and heat it in the eve as and when required. It'll soon get back to normal, with no long term issues.

Imo, dehumidifiers are only required when walls and floor are soaked and need real help drying out - this is not the case here.

The below is daughter's wee room when I collected her from Uni. Now, that's mould! And she's in the peak of health. And ironically just qualified as a theatre practitioner...

sujsuj

ThisIsWeird said:

sujsuj said:

I am seriously considering dehumidifier..I  wasn't sure it it will cause any health issues..?

Don't panic - these spots are mild by any mouldy standard. Once you've sorted the cause - and let's hope you have - it won't get any worse. And it looks as tho' you've got rid of the actual spots anyway.

Yes, mould can be a health issue, but unless you are very vulnerable, it would need to be pretty bad, and you'd have to be living in that room for a good part of the time.

What's that room used for? If it's a current bedroom, then just ventilate it during the day - flinging the windows wide open on dry sunny days - and heat it in the eve as and when required. It'll soon get back to normal, with no long term issues.

Imo, dehumidifiers are only required when walls and floor are soaked and need real help drying out - this is not the case here.

The below is daughter's wee room when I collected her from Uni. Now, that's mould! And she's in the peak of health. And ironically just qualified as a theatre practitioner...

its bed room and started ventilation now.Thanks.

sujsuj

stuart45 said:

Section62 said:

sujsuj said:

stuart45 said:

You would expect a 20 year old extension to be a cavity wall, although you can never be sure, especially in rural areas. It's quite common where I live for people to build extensions without permission, and farmers building bungalows for their kids.

This is what I can see from inside under sink. This is just inside big bush you see in the photo (you can see waste pipe). So I suppose this is part of cavity insulation done previously.

One if the issues when extending is that a previously external wall can become an internal one.  In some situations this provides a cold/damp bridge from the remaining external wall(s) into what is now an internal wall.  This is a detail the architect/builder ought to take into account to minimise the risk of problems.

That's a good.point. When a cavity wall is built against a solid wall there is a slight weakness at the join because moisture can get through a 4 inch skin relatively quickly.

I can see that now. Thanks for the detailed explanation.

Jellynailer

SujSuj as well as checking the extension damp proofing, can I urge you to check under any flooring in the bedroom where the mould spots have been remove.  Your photos of mould on the skirting boards + information that you did not notice the problem because it was behind the chest of drawers points to the mould emanating from below.

Grenage

Jellynailer said:

SujSuj as well as checking the extension damp proofing, can I urge you to check under any flooring in the bedroom where the mould spots have been remove.  Your photos of mould on the skirting boards + information that you did not notice the problem because it was behind the chest of drawers points to the mould emanating from below.

It points to mould forming due to a lack of ventilation behind furniture, and a moist wall. 

Stop being ridiculous.

ThisIsWeird

sujsuj said:

its bed room and started ventilation now.Thanks.

Cool.
There have been repeated threads on here about how to tackle windows running with condensation in the morning, and mould spots appearing on walls as winter approaches. If there's a simplistic, one-word answer that can be given, it's 'ventilation'.
A solid wall construction like yours won't help, as the surfaces will be colder than on a modern build, and the colder the surface, the bigger the attraction for cond.
If you can add insulation at some point, that should be transformative, but until then there is a routine you can follow which I believe will make a huge difference, and cost nothing. Yup, ventilate :-)
The routine in essence is - when you are not using the room, have the windows at least cracked open to ventilation setting, and open further if you can, say on dry or sunny days. Yes, it'll be cold in there - but dry. Heating off (a waste) and internal door closed (so as not to attract moist air from the rest of the house).
Come bedtime, by all means close the windows and turn on the rad a while before to make it welcoming (Smart TRVs are nice for this). Then - ideally - rad off and window back on vent before the occupant jumps under the sheets. 
A lot of moisture is produced overnight, and temps tend to fall, so if you do not ventilate that away as it occurs, you'll wake to wet windows.
Cold? Pah. Just use a good duvet. Still cold? Add an overnight leccy blanket - pennies to run. No-one should be cold.
Towards getting up time, rad on again to make the bedroom welcoming, close the window as soon as out of bed, get up & get ready for the day. Then, when existing room, rad off, crack open window for the day, and close the door (unless it's a really nice day and you want a good drying air flow through the whole house).
I can almost guarantee that this will stop any condensation and mould issues. At the very least, it'll reduce them dramatically.
No need for excessive heating, no need for dehumidifiers.