If the extension-roof defect is localised
If diagnosis identifies a limited defect and the surrounding roof and deck are otherwise sound, a reinforced local repair may be an appropriate route rather than assuming the whole roof needs replacement.
See the SealForge Kit for the reinforced local repair system. If the source is still uncertain, work through the Flat Roof Leak Help Centre first.
Widespread deterioration, structural movement, a soft or sagging deck or unsafe access should be assessed by a competent roofing professional.