Mystery water ingress

Grenage

We pulled up the carpet to decorate the room and discovered this joy.  It's slightly damp and went unnoticed due to the carpet backing.

The far wall is external and I think the water has been tracking from there towards the bedroom chimney.  There is a small amount of powdery mildew on the boards but they seem sound, to I'll pull some up tomorrow.  This had likely been a problem for at least 4 years when we moved in.

There is a large bay window outside that wall and the flashing looks suspiciously crap.  The drop is too shallow and there are multiple joins with leadmate or such.  It also seems to bend back into the wall for a cm or two.

Before I redo the flashing, how would the water get across the cavity?  There's no insulation.

TELLIT01

Although the cavity should be clear it isn't always the case.  My neighbour had a similar problem and when the builder investigated he found it was full of rubble.  Once the rubble was removed the problem also disappeared.

Grenage

But isn't that unlikely on the first floor?  I can't work out why none of the skirting is rotten or that there isn't more damage beyond the grippers rusting away.  There was a little mould on the wall behind the bedside table, so I wonder if most of the water is in the wall.

Martin_the_Unjust

Are you sure that it's not coming down the chimney? It appears to track from the chimney towards the wall, that may be due to lighting in the photo or a small slope in the floor though.

Grenage

I guess it's possible, but it's hard to know.  I'll put a spirit level down tomorrow and see which direction it slopes.

FreeBear

Looks like some numpty in the past has hacked back the flashing for some  half baked reason. There is a faint outline of where the flashing was originally that lines up with the strip towards the top of the image.

Replacing that strip of flashing is certainly a job worth doing, but I wouldn't like to say that it would fix the damp issue.

Grenage

Oh yes, I see what you mean on the tiles.   It could also do with stepping up another course, so I'll replace the lot.