Olympic freestyle: how Paris’ Aquatics Centre works for everything

Paris 2024 is intended to be the most sustainable Olympic Games yet. That is because most of the infrastructure needed for the games already exists, including the Stade de France, which has been repurposed to serve as the Olympics’ main arena.

The one major exception is the Games’ Aquatics Centre. Designed by architects VenhoevenCS and Ateliers 2/3/4, the purpose-built venue that will host Olympic swimming and diving events is spectacular, innovative and low-carbon.

More importantly, when the games are over, the centre will become a legacy community multi-sports facility for suburban Seine-Saint-Denis, which, north of Paris’ Périphérique, has few neighbourhood facilities.

The Aquatics Centre sits west of the giant Stade de France and alongside the A1 autoroute. How did you strike a balance between a building with civic presence and one that will be welcoming as a community facility?

Laure Mériaud, partner, Ateliers 2/3/4: We wanted the Aquatics Centre to be dynamic and neighbourhood-friendly. To create an appropriate scale, we placed the largest tribunes [spectator galleries] to the south and the diving boards on the east, in front of the Stade de France and motorway. The building’s massive elevations front these while the smaller scale facades face the neighbourhood. We are small but we have a ‘forme au fort’ to give us a presence in the neighbourhood.

After the games, the south tribunes will be dismantled to create the space for paddle courts for legacy use.

Cécilia Gross, architect partner – director, VenhoevenCS: If you designed a pool for the Olympics you would design a black box. We decided to design a sports centre for the legacy phase. The east and west elevations are fully glazed along with the first 3m of the north and south facades because you want the public to see inside and those inside to see out. It is magic what daylight brings to this building especially when it’s sunny. 

For the duration of the Olympics they will cover the glazing with blackout blinds to control the light for TV. 

Outside we’ve created a layered, louvred colonnade to help with solar shading, protect the public and give the building a human scale. 

What is the significance of this roof form and the use of timber?

CG: The asymmetrical 5000m² sculpted roof is supported by a catenary structure of 91 concave glulam timber beams. Its design is efficiency-driven, dispensing with volume where it is not needed. The roof is highest above the diving tower and swoops down over the 50m pool, towards the neighbourhood. This is logical as you need less height above the pool. 

The concave shape of the roof allows for a significant reduction of the hall’s volume and thus energy expended to heat it. Had we designed a box it would have been twice the volume.

We wanted to use timber from the start. For us it was the best material: it is bio-sourced, and by combining structure and aesthetics you don’t need finishes – it is everything in one. The challenge is in its design because it’s the structure that makes the space. We used parametric modelling tools to develop the roof form.

LM: We also wanted the roof to appear thin and light. We did not want big beams with wasted space between them because that would also require energy to heat, so we worked with our engineers to design it to be like a leaf covering the space.

We did not put grass on the roof but decided to make a it work as a solar farm, which supplies 20% of the energy to heat the pool. The roof is also used for harvesting rainwater for irrigation.

CG: The timber beams are 90m long but with only a 550mm x 200mm cross-section, spaced 1m apart.An extra layer of timber plank purlins running at right-angles to the beams adds stability and is a finishing layer so we didn’t need a false ceiling. You can see all the lights and ducts, which become part of the design. However, there are some larger ducts on top of the roof to keep continuity of the internal form.

Is the final scheme very different to your competition entry?

LM: The project was procured on a design build finance maintain and operate basis. The first and final designs are not different because decisions were made with the whole team – builder and future operator included.

CG: There were three rounds of the competition phase. Our concept and ambition never changed, but in every round we managed to make the building more compact, efficient and smarter, to reduce costs. The third round was the most painful. Our client La Métropole du Grand Paris said the scheme was still too expensive and we had to make it even more affordable. 

We had already removed what we could, so we had to make the building smaller. We wanted to cut 10m length from the building while ensuring it continued to work. That was when we embraced the concept of a flexible swimming pool.

How does the flexible pool work?

CG: We looked very carefully at the swimming event programme. There was never a concurrence of the swimming competition in the 50m pool and the diving competition in the 20m pool, but there was water polo, artistic swimming and diving. For water polo and artistic swimming disciplines you only need a 33m pool. That’s when it occurred to us that perhaps the pool could be made flexible. 

We worked with the pool designer to combine two movable walls and a movable floor to enable the multiple configurations. The move has been done before, but never for any of the Olympic Games.

LM: The pool does not have a constant depth. We adopted the same approach to designing the floor of the swimming pool as we did to designing the building’s roof. We did the same analytic work on the minimum depth that each event needed, and sculpted the bottom of the pool to minimise the volume of water required . 

CG: Admittedly, it costs a bit more money to build, but it does mean that you need 25% less water than you would have done if you’d taken the obvious approach, which will save money over the whole life of the building.

What is genius about it is that not only have we saved money – we’ve actually designed a pool that creates far more possibilities than before. We’ve also improved the experience for the public because they are closer to the pool and we’ve reduced the centre’s energy demand because we have made the building volume smaller.

The Aquatics Centre has been handed over and is being made ready to host the Olympic swimming and diving events in July 2024. However, for Cécilia Gross and Laure Mériaud their involvement with the Olympic Games is not yet over; it is appropriate that their final act of collaboration will be to run together holding the Olympic torch when it passes close to the Aquatics Centre on its journey to the Stade de France for the opening ceremony – probably the only architects to have held the flame in the history of the Games.