'Problem' cupboard...

Only to check if the top is closed, you can't get your head close enough to look down the cavity, but you should get an idea if the inside of the eaves over the cavity is full of rubbish brought in by nesting birds, which would probably be Starlings if there's a big enough gap somewhere.

 

Bless

 

In the meantime, you can ask Mrs. FC to clean the mold off and put a bag of cheap cat litter on the floor. Slash a hole in the bag to expose the contents. It will soak up humidity and give you time to cope.

 

The louvre doors suggest to me that the cupboard was used for linen and housed a cylinder for hot water. The era of the house also suggests that. With the cylinder in there it would have kept mould at bay. With that cylinder gone and the house now having cavity wall insulation any damp within the cavity has a bridge to cross into the cupboard. Cavity walls in earlier eras were built as that - cavities - to stop damp penetrating to the inner walls.

Has the roof felt and joists been checked in that area?

You could change the doors for a curtain which will allow more circulation.

 

@Fat Controller I've had those SRO moments and am amazed at how I cannot have noticed something so obvious

 

Off topic... when we lived in Southern Europe we moved into a freshly renovated flat. I was delighted to find so many sockets and even a phone socket in every room. That was a nod to the modern world in that time and region.

We took a phone contract and the engineer came to do his bits. After some furious testing he took the phone sockets off one by one- they were just screwed on the wall for show, there wasn't even space for any wires.

Thankfully most of the electricity sockets were real and I just didn't bother with the ones that weren't.

 

Looks as though you've found the cause and the solution Sell the unused 'stuff', fit proper louvre doors and Robert est ton oncle Oh, and you might want to invest in a woolly blanket for your knees when working at the desk

 

I meant the stuff stored in the cupboard As for the doors.....would the landlord really nitpick over their replacement? After all, the damp problem could have long-term effects on the house!

 

In most cases. Mould inside houses is down to poor ventilation. Especially during the autumn and winter periods, when on goes the heating, shut that door and keep those windows closed. It is obvious that your cupboard is the catchpoint, the corner trap. Removal of the door might help, but during the day when most folk are moving about. Go ahead and ope a window of two, get some fresh air in. On the otherhand, sometimes damp can enter from outside. The cavity walls used to cut damp and mould down. Then someone came up with the idea of cavity insulation. Damp can be caused by lack of ventilation, then on the other hand. I know of an estate built in the late 70's early 80's at Selsdon in South Croydon. Damp and internal mould became such, that the authorities actually painted some kind of waterproofing to the outside walls. You can get a polystyrene wall covering. It comes in rolls as per wallpaper dimensions. It's applied like wallpaper. It does offer some protection against damp and also cold. At the end of the day. My advice is. Ventilate.