Ask a tall-building engineer what shapes a slender tower and the answer is rarely gravity. Past a certain slenderness, wind and earthquake set the budget: the lateral system decides where the concrete goes, what it costs and how free the plan stays. In Switzerland those actions are written into SIA 261. A tower’s economics follow from how well its structure answers them with material it already needs for something else.

That is the essence of the ABZ tower rising in Zürich-Albisrieden’s Koch-Quartier. It is 85 m tall. The client is the Allgemeine Baugenossenschaft Zürich, the architects are Enzmann Fischer Partner AG and the landscape is by Skala Landschaft Stadt Raum. Espazium editor-in-chief Marc Frochaux reported on 24 September that the competition ran in 2018, the scheme holds 204 flats and targets Minergie-P-eco, and occupancy is planned for spring 2027. It is still under construction, and no topping-out date has been published.

Read it from the feet

A building knows itself from the ground up, so start there. Schnetzer Puskas Ingenieure AG’s project page describes piles 25 m long and 120 cm in diameter under the tower, inside a braced sheet-pile pit. The 25 m-high mid-rise block next door, 16 x 48 m in plan, stands on smaller bored piles and a raft. Schnetzer Puskas also engineered the TITLIS retrofit PAZ covered on 3 October. That was wind at 3,020 m and this is wind over Albisrieden, but it is the same discipline.

Above the piles stands a skeleton. Prefabricated concrete columns arrive finished and the flat slabs between them are cast in place, with in-situ upstands along the slab edges for fire protection. The footprint starts at 21 x 47 m and steps back to 19 m at level 8 and 17 m at level 16. Each setback slims the silhouette and reduces the area the wind can push against.

The quiet idea sits between the flats. The engineers describe the dividing walls as load-bearing concrete members. They give neighbours sound insulation, and they also brace the tower against wind and earthquake. A concrete inner shell in the end façades and the central access cores complete the bracing. Han Solo bragged that the Falcon had it where it counts. This tower keeps it where the neighbours meet.

The trade-off is simple. A wall that braces a tower cannot simply be removed later, so merging two flats in 2060 becomes a structural project rather than a weekend with a saw.

Building-sense: A building running this frame would feel a gust on its west face travel into the walls its occupants share, and be glad of them twice over. The walls that keep a neighbour’s piano quiet are the same walls that keep the structure from swaying.

Clusters, a roof, and the people who pour it

According to Frochaux, every three floors form a cluster of 21 flats around a shared laundry and common rooms, linked by an open stair. The roof carries a 1,700 m² shared terrace, and a reused greenhouse up there serves the integrated daycare. HRS, the general contractor, has worked the 13,354 m² plot since the foundation stone was laid on 25 October 2023. Its formwork carpenters cast slab after slab between columns that arrive by truck. Their work turns a structural concept into finished floors.

←TODAY: An 85 m cooperative tower in Zürich, unsubsidised, with its bracing in the party walls. →3012: Towers judged by how many jobs each tonne of concrete does. Fulcrum: Rent is a structural output, and the walls you build once are the walls you pay for once.

The rents bear this out. Espazium reports net rents without subsidy of CHF 1,230–1,410 for 2.5 rooms (60–68 m²), CHF 1,660–1,855 for 3.5 rooms (83–89 m²), CHF 1,930–2,265 for 4.5 rooms (97–110 m²) and CHF 2,405 for a 129 m² 5.5-room flat. That comes to roughly CHF 19–21 per m² per month across every type. It is close to the cost-rent logic PAZ traced at Kalkbreite, where Metropolis reported about CHF 2,000 for 100 m². Espazium’s 23 September survey of Swiss towers of 60 m or more made the wider point: the cooperative tower “n’est pas forcément un objet spéculatif”.

Atelier: Most offices model a tower’s structure only after the plan is settled, which leaves each wall doing one job. AI massing generators won’t raise this question, so a team that uses them has to ask it. Monday move: in your next Rhino massing model, create a layer called DUAL and put on it only the walls that both carry load and separate tenancies.

Hack: Turn the published rents into a cost-per-area check, so you can see whether a structural choice reaches the tenant. Run this in Rhino’s Python editor or any terminal. A flat line across flat types is the signature of a cost-rent cooperative, and a steep curve points to market pricing.

flats = {"2.5": (1230, 60), "3.5": (1660, 83), "4.5": (1930, 97), "5.5": (2405, 129)}
for k, (chf, m2) in flats.items():
    print(k, round(chf / m2, 1), "CHF/m2/month")

Open your current tower or slab-block study today, mark every wall that does two jobs, and count them before anyone draws a façade.