Antonelli and Herry Architectes Stack a Planted Concrete Car Park to Replace Surface Parking in Strasbourg

Car parks rarely make the case for architecture. They are usually the building a client wants least and spends least on. The Silo Parking House in Strasbourg, designed by Antonelli and Herry Architectes for the Caisse fédérale du Crédit Mutuel, starts from a different premise. It replaces an existing surface lot on the bank's Wacken headquarters grounds. Stacking the cars into a compact, ground-plus-four volume 14.75 m tall frees the land for planting and removes paved surfaces across the site.

What interests us is where the project sits in a longer sequence. The bank's Campus Vert transformation began by reworking individual buildings. The Silo is the first move that works on the site itself, and it treats parking as a tool for landscape repair. It also plans openly for a shift in how people arrive: electric vehicles, e-bikes and scooters, and a growing Eurométropole cycling network. At 12,000 m², it is a large building that is trying hard to look like less.

A Car Park That Steps Back

Seen from the lawn and the street, the building reads as a stack of terraces rather than a block. Each level carries its own band of planting, and the volume sets back as it rises. That keeps the mass legible as a series of horizontal lines instead of a sheer wall of parking.

The cars remain visible, and that is the right call. The project does not disguise its function. It accepts the parked car as part of the image and wraps it in enough green that the street edge feels inhabited rather than serviced.

Slab Edges Built to Carry Planting

The defining detail is the slab edge. Rounded concrete floor plates cantilever past slim columns, and vines and grasses trail over every lip. From below, the stacked curves read almost like contour lines, softened further each season as the planting grows in.

This is where the green ambition either works or fails. A planted car park only convinces if the planting looks like it belongs to the structure rather than being bolted on. Here the planters sit inside the slab profile, so the greenery is part of the building's outline.

Screens, Stairs and the Evening Lantern

Vertical timber slats and concrete slat screens filter views into the decks and give the facade a finer grain between the heavy slab lines. At dusk, the open stair tower glows through these screens and becomes a small lantern at the campus edge.

The stair deserves credit. Open, lit and visible from the street, it invites people to walk between levels rather than hide in a lift core. For a building type known for grim stairwells, that is a quiet gain for pedestrians.

Bicycles Get the Good Floor

The bicycle halls are the clearest sign of where the client thinks mobility is heading. Green steel hoops, a pale green floor and painted lettering give cycle storage its own identity. The halls are laid out with a central path leading to a doorway, so arriving by bike feels designed rather than tolerated.

We would like to see this standard everywhere. Too many corporate campuses tuck bikes into leftover corners. Here the cycle program shares the same structural quality as the car decks: tapered columns, coffered slabs and warm light.

Structure as Ceiling

On the lower levels, the waffle and ribbed concrete slabs do the work that finishes would do elsewhere. Tapered columns gather the load and strip lights run between the coffers. The result is a ceiling with rhythm, which matters in a space people move through slowly and repeatedly.

The framed view through a deep wall opening shows how much the designers rely on that structure for character. There is no applied decoration, and none is needed.

Painted Floors and Lit Aisles

The parking decks use a restrained graphic system. Black-painted bays with white stall lines sit against raw concrete aisles, and painted arrows handle wayfinding. Board-marked ceilings and a single black cable tray keep the services orderly.

The best moments come at the ends of the aisles, where daylight and foliage appear through the open edge. That glimpse of green at the end of a drive lane does more to orient a driver than another sign would.

Decks Open to the Trees

The open decks keep their edges low, so treetops and vines spill into the parking floors. An angled soffit frames the neighbouring office block across a planted ledge, tying the Silo back to the headquarters it serves.

Natural light and cross views also make the building easier to use. You always know roughly where you are relative to the campus, which is more than most multi-storey car parks can claim.

A Rooftop Garden and Ground Returned to Planting

The roof is the payoff. A timber boardwalk winds through shrubs, tall grasses and young trees, turning the top of the car park into a garden rather than another parking deck. At ground level, a curving granite sett path meets the boardwalk and runs through planting where asphalt used to be.

Landscape architect Acte 2 Paysage gives the de-paving claim physical form here. The parking did not disappear, but the open lot did, and the land around the Silo now reads as a garden with a building in it.

Plans and Drawings

The site plan shows how compact the footprint is next to the road and the surrounding blocks. The floor plan sets stall rows and a single drive aisle between stair cores and service rooms. The roof plan lays out the planted deck around a central grid and a small stair tower.

The section and elevation confirm the low, stepped profile beside the taller glazed headquarters, with trees planted along the roof edge. The detail section of the rooftop pavilion, drawn at human scale with a raised deck and planting bed, shows that the roof was designed for people as well as plants.

Why This Project Matters

Most campuses treat parking as a sunk cost: as much asphalt as needed, as cheaply as possible. The Silo argues that consolidating cars into a well-built structure is one of the most effective landscape moves a large landowner can make. Stack the cars and you get the ground back. Give bikes a proper hall and you signal which way you expect commuting to go.

The open question is adaptability. A building planned around changing mobility should ideally be able to change its own use as car numbers fall. The generous spans, open decks and cycle program suggest the designers were thinking along those lines. Either way, Antonelli and Herry Architectes have shown that a car park can serve a campus landscape rather than consume it.

The Silo Parking House by Antonelli and Herry Architectes (lead architects Thierry Herry and Roland Antonelli), Strasbourg, France. Area: 12,000 m². Completed 2024. Engineering: OTE. Environmental consultant: Otelio. Landscape: Acte 2 Paysage. Photography by Valérie Trégan.

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