Campbell Optiker — established in Hamburg in 1816 — fitted out its retail premises at Neuer Wall 72, occupying the ground floor and basement of the Paulsenhaus on Hamburg's premier shopping street. The fit-out required connecting the two levels operationally: the basement holds the back-of-house functions (office, workshop, storage), while the ground floor carries the retail sales floor and refractive testing rooms. The connection was made via a new Dolle Calgary prefabricated spiral staircase, installed through a new circular opening cut into the historic reinforced concrete slab between the two floors.

That single opening triggered a full structural re-verification of the entire slab — not just the area around the cut. The RC slab bears on two structurally different supports: a masonry wall on its north side and an existing steel beam on its south side. Both bearing conditions had to be checked independently under the redistributed load that results from removing part of the slab. The stability of the external wall was also re-verified as part of the scope.

CN Europlan delivered LP1–4 structural design together with consulting services. Opening a historic slab redistributes load across the entire bearing system — treating the cut as an isolated change would have missed the full structural consequence of modifying a slab with two independent and fundamentally different bearing conditions.

Key Takeaways

• One spiral staircase opening triggered a full-slab re-verification: Installing the Dolle Calgary spiral staircase required a circular cut through the historic RC slab. Load redistribution across the full slab area — not just the cut zone — made a complete structural re-check necessary.
• Two structurally independent bearing conditions on one slab: The north side bears on masonry, the south side on an existing steel beam — two systems with different stiffness and load-transfer behaviour, each requiring its own independent structural check under the modified load state.
• External wall stability re-verified, not assumed: The scope extended to confirming the external wall's structural integrity, ensuring that the slab opening had no consequences for the load-bearing elements beyond the slab itself.