mould problem on walls

trixyben

my neighbours house which is an old house its stone walls with no cavity, they live there now 2 years and are having a problem with mould on the walls, the mould is even getting onto cloths in the wardrobes and just today they seen mould over the end of the mattress which is against the wall!!

now i knew the previous owners very well and they never had any issues with the mould, the heating system hasnt been changed, the house gets well aired and heated...

whats triggering the problem does anyone know? what would you do to tackle the mould?

BryanF

trixyben wrote: »

my neighbours house which is an old house its stone walls with no cavity, they live there now 2 years and are having a problem with mould on the walls, the mould is even getting onto cloths in the wardrobes and just today they seen mould over the end of the mattress which is against the wall!!

now i knew the previous owners very well and they never had any issues with the mould, the heating system hasnt been changed, the house gets well aired and heated...

whats triggering the problem does anyone know? what would you do to tackle the mould?

has anything changed internally? - insulation, draft proofing, windows, painting and so on... are you sure the house is being 'aired' or a better phrase vented properly?
start with cleaning mould, I generally use a damp meter to check wall/floor moisture levels and RH sensor to check humidity levels. often a visual inspection will indicate what's potentially causing the problem (or problems)

lack of ventilation
sources of moisture (drying clothes, cooking, breathing etc)
lack of heat
a leak, damp infiltration or rising damp

externally has anything changed? -landscaping, painting, cracks, gutters, chimney/ window reveals, ground level. carefully inspect and eliminate the possibilities one by one

isaos

Hello,
I don't have the knowledge to give a pertinent and technical answer to the thread, and I would refer anyone to BryanF posts on the matter. This is personal observation if it can help as it might apply to your case, and also a question.

In the house we just bought, 2 to 3 ft stone walls, house built around 1905, one south facing gable wall shows a lot of dampness and mould, some parts of the inside wall are very crumbly, and we haven't yet checked all the damage on the outside which has been painted with weathershield at some stage.
The north facing gable wall has been left unpainted, and is in excellent condition.

This leads to a question: Does weathershield paint (or whatever new outdoor paint) stop the stone wall from breathing and keeps dampness in? and if this is the case, how get rid of it, and at what cost?


Isaos

beyondpassive

When the house is rapidly heated it raises the temperature of the air and increases the capacity of the air to carry moisture, lets say 18 degrees at 86% RH.

However due to the high rate of heat loss in some rooms like bedrooms with a large enclosure area, the surface temperatures temps in some corners cannot get above dew point (<12 degrees) and as the air temp drops, the water vapour condenses on the coldest surfaces. Add the presence of spores or ineffective ventilation and you get mould. Lime based materials are generally anti fungal, but most modern finishes arn't. You can get paints for clean rooms but this isn't dealing with the problem that the house cannot tolerate intermittant heating and cool down.

This is now a problem in semi occupied celtic-tiger estates, where the heat loss through party walls and floors to an unnoccupied neighbour is causing mouldy walls, one solution is extra insulation (not dry lining though) and use of decentarlised hole-in-the wall mechanical vents with heat recovery from the big fan companies (sounds like vent-axe and expel-air)

So they need to insulate and ventilate. Alternativly they could look at a heating system that keeps all surface temps above dew point, but you'd want a cheap fuel source for that to be effective.

isaos

We just discovered today that the main reason for the state of dampness of this big gable wall (actually 4ft!) was.. a leak from an (old) pipe going to the attic tank through this huge wall.
Thankfully it hadn't been raining for a good while, so we were able to identify the leak as it was the only logic explanation to the wall becoming so damp.
Attic tanks should be banned- in my opinion!