Bay Window leaking somewhere

[Diamond40]

Hi
I’m new to this site but was looking for some help, I have a bay window and we noticed a yellow Mark a few weeks ago, well now it has gone really big so I’m thinking water is getting onto the bay window roof some how I’m not sure if it’s the lead flashing or the tiles or the bricks as the mortar is loose in parts.
I’ve tried to post a pic to show anyone who can advise.
Thanks

 

[^woody^]

How long ago was the cavity insulated?

Someone will need to investigate the tiles and felt and flashing above that area. If no problems, it's the wall or window above, then the main roof eaves felt to be checked.

 

[Diamond40]

The cavity was insulated about 6 years this has happened in the last year but really bad now not sure if it’s with all the snow we have had

 

[Wayners]

No cavity trays above bay I guess and water getting in cavity causing the stain

 

[Diamond40]

Sorry to sound stupid but what does that mean

 

[JohnD]

edit

my mistake, not a flat-roofed bay.

 

[^woody^]

Sorry to sound stupid but what does that mean

All cavity walls should have a cavity tray in them above any opening, to stop any water running down the cavity from coming out the bottom. Many old walls don's but are OK. The problems arise when other defects in the wall or roof above let water into the cavity.

 

[datarebal]

check window