Salle Sportive Pierre Chevet / lemoal lemoal
Address
Allée du Bois, 77183 Croissy Beaubourg
Program
Hall for physical exercise and changing rooms
Client
City of Croissy-Beaubourg
Status
Complete
Cost / Floor area
€ 1,100,000 excl VAT (with external works) / € 139,000 excl. VAT (structural works)
380 m²
Calendar
Construction works 11 months
Delivered in January 2021
Team
lemoal lemoal architecture paysage • architect
Axoé • All trade works
Apave • building control office
ARC 77 • H&S coordinator
Cabinet BEC • outdoor facilities
Construction companies
Baticible • Structural works
Cruard Charpente SAS • Frameworks
Collin étanchéité • Roofing, waterproofing, facade
ECNR • Outdoor joinery
Ageco Agencement • Interior joinery
MS BAT • Partitions
Sarl CBT • Hard surface flooring
Sarl Bernier • Painting, cleaning
Magny électricité générale • General electricity
Seveste • HVAC, plumbing
Photos & copyright
Elodie Dupuis, Bertrand Fompeyrine, Vieille matériaux • Libre de droits
Prizes
Gestes d’Or, catégorie Innovation • 2020
Bilan de l’Architecture Locale, CAUE 77 • 2020
Text description provided by the architects.
Lemoal Lemoal architecture and landscaping office has delivered the first new public building constructed with hempcrete blocks in France, the Pierre Chevet sports hall for the town of Croissy-Beaubourg (77). The fruitful collaboration between manufacturers, architects, and construction companies was the opportunity to experiment with an innovative and sustainable implementation.
Context and design brief
Croissy-Beaubourg is a suburban commune of Seine-et-Marne on the outskirt of the metropolitan area of Paris. The characteristic of this typical urban fabric is with a strong dominant residential. As an echo to a city center, the project is a new multipurpose sports hall located in the center of a set of public facilities – school, gymnasium, multipurpose room and leisure center.
In addition to this particular context, it is important to clarify the procedure of the project which is not the result of a traditional architectural competition. In order to help the small cities, we develop in France what we call ‘’une procedure adaptée’’ which could be translated as ‘’adapted process’’. The word ‘’adapted’’ is here very important since it will illustrate the aim of adapting a project to a budget beyond any architectural considerations. In the way, the scheme is presented as a proposal mainly based on a methodology and the capacity of the office to propose a solution which will be able to found the good scale for the municipality.
It means that when we start the contract, we had to design the building, find the right implementation in the context and define all the characteristics of the future building.
The use of hemp
In response a constrained budget - it was estimated in the design brief around six hundred and fifty thousand euros which could be converted almost five hundred and fifty British pounds - the structural principle of the project was guided by the desire to use sustainable and multi-performing materials.
The engineering office all trades proposed me to use hemp block during a meeting. We never heard about of hemp block before. Of course, I had seen operations done based on concrete hemp cast in place, but I was not aware of this type of hemp made product. He described me all the benefits to use that specific type of material for our project: versatility, thermal/ acoustic/ structural and fire-resistant performance.
Also, and that was a good point: grown in France, the fibers are assembled within 500km of the project site. Hemp block participate in valuing short-term sectors.
Pierre Chevet Sports Hall is the first public equipment built with hemp block. This constructive process has been possible to respond two requirements.
On the one hand, it participates in engaging the actors in the building sector toward an ecological transition. The project provided an opportunity to a masonry company to this technique.
On the other hand, this constructive technique does not require specific certifications or qualifications. For example, on small-scale projects such as ours, small local businesses were not excluded and could therefore respond to the call for tenders.
The technical implementation
Similar to traditional cinder blocks, these are products based on CHENEVOTTE. It comes from the inner part of the stem (also called straw) which is then cut mechanically to obtain hemp shavings. This an agricultural material until then without outlet. This base is made very compact thanks to a quick natural cement binder developed by Vicat, a French cement group based in my natal region Rhone Alpes. These elements are initially designed for a high speed of implementation – compared to a technique by projection – because they provide delays and drying conditions. Measuring sixty by thirty-by-thirty centimeters, the weight is almost eighteen kilos, they are easy to cut. The blocks are not glued, they are just nested.
The funny fact is, the construction operator– a former stonecutter – found the same assembly techniques as in stereotomy.
Structure
Our will was to free up as much space as possible for this small project without a floor.
The axonometry reveals the structural principle of semi-porticoes and wooden joists supporting each other on a hemp block wall on a reinforced concrete post-beam frame. The peripheric walls forms a U from 3 meters high and rising up to 5 meters for the central wall. The 42 m3 of walls were mounted for ten days. The lower part houses the elements attached to the dance hall (hall, changing rooms, storage and technical rooms). The main room, open to the outside, is the large sports practice room.
These half wooden porticoes allow to free the maximum of space.
Finishes
Because we wanted to offer durability to the facades, we decided to use full height fiber cement panels (Equitone panels). Keeping the standard format of the panel has been the starting point for the pattern layout of all the facades.
But how to attach a 10 mm thick and heavy cladding panel of 16.8 kg/m2 to a hemp wall? Throughout the project, we were able to discuss with the head of Vicat who had developed the technical requirements for hemp block. I must say that this project was a collective work between each partner, the design office, us and the manufacturer.
Pierrick Serres from VICAT intervened on that question because it was the first time that a facade panel was fixed to a wall like this. We had to review the hook systems, as it was impossible to create intermediate points. The structure therefore starts from the low point on the ground – the cellular concrete tab. Then we came to fix the holder of the large omega in the head of the pole filled with concrete, which offers the panel a resistance to pullout and wind. The waterproofing was made by a simple primer/coating applied to the hemp blocks prior to panel installation.
It helps to reduce the number of different materials used. Due to its multiple qualities, the hemp block makes it possible not to use dubbing and to reduce the thickness of the walls to the essential.
The inner surfaces were treated with hemp coating, in low parts.
Free of insulation and gypsum board, hemp block also offers sound absorption properties of the order of 43 dB. That’s why in high parts of the dancing room, the blocks are left visible, in order to preserve the acoustic qualities.
We have estimated an additional cost of about 30 to 40% on the supplied-posed price, which, out of the total amount of the operation represents 2% on the construction global cost.
So, the main challenge was to convince the client that hemp is a good alternative to concrete, because since the beginning, the municipality had no specific requirement about the employment of bio sourced product. They were not implicated at the time of what was being prescribed and stopped at the word “cinder block”. We had to explain that this material allows substantial savings in long-term approach. It can represent, according to some studies, up to 70% of heating savings in the case of a building with high thermal performance. According to the modeling done by our engineer, primary energy consumption is estimated at 167 kWhep / m2 per year (Class C), with a gas consumption reduced to 42.7 kWhep.
This modest project was commissioned by the city without performance requirements, label or certification. We carried this willpower to use hemp without any obligation. The figures provided today are therefore not the result of a regulatory requirements, but just show our individual desire to go further with the support to all our partners.
As a adapted process we tried to find a solution that could prove to the client that the ambition of a project is lead by its scale or budget. In the case of this project, we wanted to show that even in a very small city…. sustainability could always be used as a flag.
