Visible cracking or splitting
Lead that's cracked, particularly along fold lines, has likely fatigued from years of thermal movement and won't reliably keep water out much longer.
Lifting or displaced sections
Flashing that's visibly lifted away from the surface it should be sealed against has already lost its effectiveness at that point, whatever the rest of it looks like.
Repeated leaks in the same area
If a junction has needed repeated repairs, the underlying leadwork is probably due a proper replacement rather than another patch.
Age, even without obvious damage
Very old leadwork can be nearing the end of its practical life even without visible faults yet, particularly on properties where the rest of the roof has already been replaced once.
If you're not sure whether your leadwork needs attention, our team can assess it as part of a routine inspection.