Damp patch in wall, just below ceiling. Help!

[Teachmesomethingnew]

I have just noticed some yellow coloured water running down the wall in my bedroom. The bedroom is upstairs and the water is a small number of drips coming from the join between wall and ceiling in the corner of the room. The corner is the outside edge of the house. The plasterwork did have cracks in it before we decorated last, but now feels damp. The ceiling is slightly spongy to the touch in this corner. The loft above the area is dry and well insulated.
There are no visible signs of damp (dark patches) on the outside walls.
The fascias and guttering are all uPVC replacements. The fascia ends near this area as it runs along the front of the house and not the side. The gutter is old and a bit askew but is held away front the house by the fascia (design is a bit like a large box section of about 300mm size so the roof goes well over the affected area. again there are no obvious problems here. I am stumped.

Any suggestions as to what might be causing this?

Thank you

 

[greengrass]

Sounds like a cracked, broken or slipped tile/slate. You say the facia and guttering are forward from the building so I assume it has a soffit board underneath or it's an open soffit.
Look in the attic and see if you can see daylight further up from the damp patch on the ceiling. also feel the rafter for signs of wet. Obviously turning of the attic light or torch will show the direct daylight clearer.

You could try looking in the attic when it's raining and see where it's coming in as it sounds to me like a broken or slipped tile further up the roof if you say the roof in area of damp is ok. Water can run from the ridge on the rafter and not show on the ceiling until it gets to the bottom then drops off. Afraid it's trial and error process unless there are tiles obviously missing. I've repaired many rooves where tiles had slipped or broke 3/4 up the roof opening up the lap joint rain has run down inside and show at the bottom just like yours. Sorry can't be anymore helpful.