Is moss causing problem?

[bathtub tom]

I've got a damp patch (about 1m x 300mm) above this window in the ceiling of a shower room. I suspect it's caused by the moss. Would spraying with glyphosate remove the moss? It's a bungalow built around 1960.

 

[Wayners]

Wet and forget.
Buy some and test yourself.

Cheap wet and dry vac and some waste pipe. Make a gutter vac...

Yeah it's a problem many ignore

 

[aveatry]

The moss will end up in the gutter and block it but I am not sure the moss is causing your damp patch. It could be that lead flashing on the end of the pitch during heavy rain shooting down and being directed under the tile
Also that lead flashing cut into the bricks doesn’t seem to be doing anything, it should be sitting on top of the tiles. Is water getting down there.

 

[StephenStephen]

Glyphosate doesn't kill moss

I very much doubt that the moss is causing the problem

You've got some odd looking flashing there that a professional might be able to suggest a correction to

I suspect the damp patch is caused by a combination of lack of ventilation, and poor insulation above the shower room ceiling

 

[chriskernow]

I would get someone reputable in to check that flashing.

 

[bathtub tom]

Update.

Had a roofer look at it and in their opinion, there's nothing wrong with the roof. They spent some time in the loft and reported the plasterboard was dry up there and only soggy on the underside, suggesting it's a condensation problem. When we bought the place, I uprated the fan to 90 m3/hr from the original (the timer keeps it running for around 20 min after switching off). The room's about 10m3.
I guess I need to consult an HVAC expert.

 

[^woody^]

The type of stain is normally a good indicator of the cause, if you have a clear photo to upload

Moss in itself is possible but least likely

 

[HERTS P&D]

Close the window and use the fan every time the bathroom is being used.

Andy