Preserving a listed façade while rebuilding the interior to a modern standard.
A listed façade fixes the rules before you draw a single room. The windows can't move, the rhythm of the elevation is protected, and the structure often has to be preserved alongside it — so the interior gets rebuilt around constraints that are already set.
That's why no two layouts in the building are the same. Each apartment is drawn to the openings it inherits, which makes the restoration slower and more expensive — and the result far harder to replicate anywhere else.