Have you read the thread? the stack has been removed under roof level already.Because if the stack is removed below the roof line then the stack above the roof line is no longer supported rom underneath.Why would I need scaffold if the stack has been removed below roof level and the roof made good?
So the scaffolding will be needed for safe access to the stack to ensure that either 1/ it is securely attached to the wall and the wall is strong enough to support it or 2/ the now un-stable stack above the roof can be removed before it falls
Read the thread its pretty self-explanatory.