Damp

[LP07]

I live in a first floor flat that is 35yrs old. I keep it warm (it had new gas central heating 5 years ago) and well ventilated but I've recently developed a patch of what I think is damp in a corner of a bedroom. Its just above the skirting board and in the far corner of the flat where two exterior walls meet. The paintwork has cracked badly and there are black marks visible through the cracks. I've peeled some of the paint off and can see black marks on the pink plaster.

This is the coldest corner of the flat and is on the opposite side of the room to the radiator. I also have a really large window, almost floor to ceiling in height which is always cold in the winter and is very close to the damp patch.

I've recently found out that the tenants in the flat below have moved out because that property suffers badly from damp including black and green spores growing on walls and furniture.

I'm unsure whether my damp problem may be caused by rising damp from the flat below, is there a simple way to assess this without accessing the property below?

The loft insulation above my flat is way below standard and I'm concerned that if I renew this and bring it up to modern standards, it may trap more moisture in the flat and make the damp problem worse.

Any help or suggestions would be gratefully appreciated.

 

[foxhole]

Damp can't rise, insulation can't trap moisture.
You said it is well ventilated but if that were the case you would not have the condensation causing your damp.
You need better insulation and ventilation.
Do you have mechanical ventilation in kitchen and bathroom?
Do you dry clothes indoors?

 

[Johnmelad]

Have a look here...

http://www.diydata.com/problem/condensation/condensation.php

 

[misterhelpful]

It sounds like a typical condensation case, as foxhole has alluded to. You could try using a small dehumidifier, if you can't improve the ventilation any more, and see if that solves the problem.
If there is a piece of furniture placed in the problem corner it will be restricting the airflow significantly so it may need to be move or pulled away from the wall/s a bit.