Planning Permission - Bay Window

[NomadicTurbo]

Trying to get my head round what is required from Building Regs & Planning Permission to replace a leaking bay window flat roof.

We currently have a lead flat roof on our ground floor bay window, which is now split and taking in water. Speaking to a few different roofing companies, they've all suggested changing it from lead to Firestone Rubber.

Does this fall under Permitted Development as it will not alter the size of the roof?

My thinking is that Building Regs are required as the material of the roof will be changed. I'm awaiting a response from the local Building Regs office.

[Quhet]

Unless the appearance of the roof is changed significantly (or a listed building), you shouldn't require PP for this