Finding the Leak on a Bay Window

Newsletter ▶ https://skill-builder.uk/signup ◀

Roger is looking at a leaky roof for Chris.

Here’s the message:

Moved into a new Taylor Wimpey build in November, approximately 13 years old.

Notice staining above the bay window on the plasterboard. Blockwork saturated behind the lead flashing, dripping down (where I’ve ripped off the plasterboard) and onto the internal wall.

It seems worse with wind-driven rain; it doesn’t occur with just rain.
is it the brickwork? Cavity trays? Flashing? The roofer thinks nothing wrong with flashing.

Thanks to @andyglasgow4033 for suggesting the Macchu Pichu location.