Flame Zone Renovations - Joining New to Old

Hi,
been searching through BCA, AS3959, and lots of internet searching, interested to see what people have done where a new renovation that has to be done to BAL-FZ (Flame Zone) is joining onto a 1970's project home?

The original house has a lot of wood cladding, window frame etc... almost all framing is oregon and windows are cedar, but it will have a Flame zone spec roof fascias and eves.

(Picture is not my house - but similar enough to show the issues where the windows meet the roof and there is a large gap that the builders say they wil just bridge with Fibre Cement)

The builder says they can just butt joint the flame zone eve (eg 15mm plywood, 16mm fyrechek plaster, 4.5mm fibre cement) up against a 50yr old piece of western red cedar and it's ok - doesn't make sense.

This can't be a new problem, what did the building consent conditions and the building certifiers say about this?

Was it just passed or did they make the new renovation section continue on until it joined with a more compliance material eg Brick, etc..

My main issues is the windows - the window frame run floor through to the roof without a break.

Interested to hear peoples experiences.
Thanks

in victoria only new work needs to be bal level
unless you renovate more than 50%, then you must bring whole home up to bal requirement
so the way i interpret that is the same as your builder

Aussieta is correct, AS3959 and the NCC-BCA relate to "NEW WORK" so if you're renovating only the new works are required to meet the standards. If they take the cladding OFF, then it's new work and needs to comply if they butt up against, the joint must comply.
Craig