Damp and mould behind bookcases and wardrobes

[d000hg]

We've discovered quite damp patches, with mould, behind two units which were moved after a few months in position, both on exterior walls in our ~1870 Victorian house. There is no air-gap between brick courses.

My guess is that these walls are prone to condensation similar to single glazing, but it is only causing problems behind units due to lack of air movement. Is that likely? If so are there standard tricks to prevent this somehow... I don't want to have to move units periodically to preserve my walls, OR to have mouldy wardrobes in case this permeates into the inside.

Traditionally, our house would have surely always had this problem - would furniture be built so that it just DID get damp on the back but it didn't transfer through?

 

[JohnD]

yes, this is a typical spot for condensation.

What do you do to minimise humidity in the house?

In 1870 people had draughty houses, draughty windows and open fireplaces, which gave lots of ventilation. They seldom had hot baths, never had hot showers, and did their washing once a week, using washing lines to dry it.

 

[d000hg]

What can we do, easily? I don't really want to try and dry all the air in the house but could I put something behind cupboards?

 

[jj4091]

Leave a 6 inch gap between them & the wall.

 

[JohnD]

do you drape wet washing in the house? Do you use effective extractors in bathroom and kitchen? Do you air bedrooms daily?

Is there a cellar? Are the airbricks to ventilate the floor unblocked and free of dirt and cobwebs? These are points that help a lot. There is also a possibility in older houses of leaking drains and pipes in, under, and beside the house, and raised external levels of soil and paving.

 

[endecotp]

How do you dry washing? Do you have extractor fans in kitchen and bathroom?

 

[d000hg]

How do you dry washing? Do you have extractor fans in kitchen and bathroom?

We dry it in a room that has
a dehumidifier. We have fans... though we also have humidity meters and they show it being ~60% right now which is not bad (as compared to 85% in our pantry!)

 

[JohnD]

is the damp patch in a bedroom?

 

[endecotp]

Right now the most humid room in my house is 42% - and that's a bathroom where I am (unusually) drying clothes!
You need to get the humidity right down.

 

[foxhole]

We dry it in a room that has
a dehumidifier. We have fans... though we also have humidity meters and they show it being ~60% right now which is not bad (as compared to 85% in our pantry!)

You can’t dry clothing indoors without causing problems, so remedy is easy as you created the problem.

 

[d000hg]

Right now the most humid room in my house is 42% - and that's a bathroom where I am (unusually) drying clothes!
You need to get the humidity right down.

How warm is your house and what's the weather?

 

[endecotp]

How warm is your house and what's the weather?

Indoor, 18 C, 42 % RH
Outside, about 7C, not currently raining but ground is damp.
(Edinburgh.)