mould puzzle

[sawdust1]

Have been asked to look at a property that has some mould about 6 inches wide along the bedroom walls where the internal side of the wall meets the ceiling on the external walls in all 3 bedrooms.
On inspection of the loft space i was expecting to see damp running down the tarred roofing felt and wetting the loft insulation and ceiling plasterboard, but everything in the loft was bone dry.
The property is in a row of 8 and has wide plastic soffits. The mould is on both sides of the property so its not from a leak.
Just can't see what is causing this to happen any suggestions ?

 

[Phil Pascoe]

Bearing in mind that it's abutting an external wall in all cases it sounds like a cold interface causing condensation rather than any leak.

 

[Wuffles]

You probably already suspect condensation.

Edit: posts crossed, that was to the OP.

 

[mind_the_goat]

Have a similar issue in a flat I look after. I have put it down to the tenants air drying clothes, and probably having pots on high boil in the kitchen with the windows closed all the time. There is also mould on the uninsulated loft hatch.
I wonder if your property has foam or loose wall insulation which has settled leaving a cold strip along the top, combined with high humidity.

 

[RobinBHM]

I guess the house hasnt always had this problem? Has something changed to have caused it?

Maybe the house had cavity wall insulation fitted? -may be the top of the walls have no insulation allowing that section of wall to be too cold. Or maybe the top of the inside skin of the cavity wall is getting very cold from the loft or draughts through the soffit / fascia.

 

[Wuffles]

If it's any consolation, I've seen this before, it appeared magically in a property that was fine for years. Cause? Change of tenants.

The new tenants preferred to dry clothes on radiators. Explained to them that the condensation they were complaining about was caused by them and the problem went away after some education about the vents in the windows they'd put tape over.

 

[porker]

as above. Sounds like a cold patch. I get the same in my daughters bedroom. Not mould but condensation in a strip. We got a drimaster positive pressure system and its really helped. 100+ year old house with solid walls

 

[sawdust1]

Thanks chaps for the replies a lot to mull over.
Actually the mould is on the ceiling where it meets the wall, would cold bridging on the wall still cause this ?
The occupier is a tenant, i will ask her some questions regards the idea's put forward.

 

[Fatboy]

my day job is a consultant to letting agencies, I seem to spend half my working day advising tenants about ventilation and heating and how to live comfortably in a modern centrally heated home without turning it into a swimming pool.

 

[Jacob]

Condensation.
We have fitted simplified "Passivent" extraction to two bathrooms and it works really well - better then expected as I thought it sounded too good to be true.
If anyone has a shower or a bath it opens wide very quickly and all steam is gone in 20 minutes or so. If the heating is on and humidity is low, it closes right down to just a small gap.
The idea is that air is drawn from the most humid parts of the building and replaced by air drawn through the other (drier) rooms
Fairly cheap to fit, costs nothing to run, requires no intervention or adjustment.

 

[acewoodturner]

Hi Jacob
Just been on their website and was quite impressed. Cant find out where to buy one and what the price is. Can you give me the details please.

 

[Jacob]

Hi Jacob
Just been on their website and was quite impressed. Cant find out where to buy one and what the price is. Can you give me the details please.

Buy from them direct. There are other brands. Most of the installation you could knock up from other sources - the key thing is the ceiling open/close vent. Their actual roof vents were poor quality (but we got them in) - you could probably do better from Screwfix.

google passive ventilation systems

The main thing is to keep it simple - the basic idea of taking humid air from bathroom and/or kitchens and having it replaced via normal leakage from the rest of the building, is actually very sensible.