IStructE 2024 Structural Awards winner in Rwanda

Denise Chevin takes a closer look at one of the Institution of Structural Engineers Award winners, the Rwanda Institute for Conservation Agriculture.

In the industry’s push to reduce embodied carbon, it will come as no surprise that the Institution of Structural Engineers (IStructE) chose a project achieving exactly that as a winner of its 2024 Structural Awards. But what makes the Rwanda Institute for Conservation Agriculture (RICA) project so remarkable is that it has managed to embrace all facets of sustainable design and construction despite being built in a seismic zone.

The 3,400-acre teaching campus, located near Kigali, Rwanda, is for training the next generation of agricultural leaders. It focuses on sustainable agriculture, conservation and entrepreneurial approaches to land use and farming in Africa, and the way it is designed and constructed honours that ethos.

As the IStructE judges remark: “Every aspect of the concept was sustainable and tried to align with as many of the UN Sustainable Development Goals as possible. Low-carbon and locally sourced materials were prioritised. There’s a huge solar farm on-site so it provides all of its own energy year-round. It collects the rainwater that lands on the site and on the roofs, reuses as much as possible, and any spare goes back into the adjacent lake.”

Staying local

Its construction was designed to boost the local economy and train local people in traditional building techniques – as well as the seismic requirements of modern codes of practice – reviving skills that were going out of fashion.

In all, 90% of the 2,500-person workforce came from the district; 35% of the construction budget was spent on labour; and 90% of the entire budget was spent within 500 miles of the site.

Another notable aspect was that more than half of the project’s leadership team were women – a rarity on construction sites in Rwanda, and considered by the team behind it as important for gender equity and inspiring future generations.

The project was designed by MASS Design Group, a non-profit architecture and design collective founded in 2008, with support from engineering behemoth Arup. The acronym ‘MASS’ stands for Model of Architecture Serving Society, reflecting the organisation’s mission to leverage design and architecture to address critical social and environmental issues – for example, it was instrumental in recruiting women on this project. MASS led the planning, architecture, landscape, engineering and construction, working with the Howard G Buffett Foundation, which conceived and funded it.

Low-carbon design

The new campus design included landscaping, accommodation for students, teaching space and barns for livestock. There are more than 50 buildings of various sizes on the site. The two largest ones are the accommodation and workshop block for students, which takes a figure-of-eight form, and a rectangular building where the dining hall, library and staff offices are located.

Across the whole campus, upfront embodied carbon including structure and architecture is about 60% less than a business-as-usual approach, says the IStructE. This was achieved by combining quartzite stone foundations, compressed stabilised earth block walls and timber roof trusses – all low-impact materials. A small amount of concrete and steel was used where required to add earthquake resistance, but this was minimised as far as possible. The structural materials determined the architectural form: large roof overhangs protect the earth walls from rain, and the structural grid is governed by 4m timber lengths to minimise waste.

One of the judges explains that constructing the foundations out of stone was similar to building a dry-stone wall, although these stones were grouted together for extra stability. The stone blocks were rough cut to different shapes, and the masons were trained to find blocks that fitted together to form a footing similar in depth to what you would find under a typical UK house. Concrete beams were fitted on top to tie it together and strengthen it so to withstand seismic movement.

Structural challenges

Adopting this form of construction threw up two technical challenges for the engineers, the first one being that both of these two construction methods – earth block construction and stone foundations – are not covered by the codes of practice Rwanda usually adopts (mostly Euro codes or local codes based on Eurocodes). Instead, the project’s engineers used New Zealand codes, which are designed to withstand earthquakes. This added to the technical challenge of pairing the design logic in a New Zealand design code with the loading requirements in Eurocodes.

The second technical challenge was also related to seismic issues – how to use earth as a construction material. The judges note: “Earth is very weak and it’s very heavy, and it’s also very brittle. So weak, heavy and brittle are probably the three worst qualities in a material you could pick when it comes to designing in a place that’s got earthquakes. Compare a slab of dark chocolate that’s been in the fridge and is very brittle with a Mars bar that’s been left on the sofa and has become warm – when you bend that it goes gooey. That’s what you want in a building material for earthquake zones, because it allows the building to move and redistribute forces. So, the team at MASS and Arup had to work extra hard to make these weak, heavy and brittle materials withstand the earthquake forces present in Rwanda.”

Using earth blocks was fundamental to the sustainability aspects and creation of local jobs. That meant designers had to incorporate ways that would allow the building to move. At the outset buildings were conceived as simple shapes – even the figure-of-eight building was divided into seven blocks, each with a simple shape, though you only notice this from above – rather than a continuous structure.

So why design a building in the form of a figure of eight in the first place if it provides engineering headaches? The answer comes down to the function of the building itself, as the internal courtyards facilitate students connecting and learning from each other.

Technical innovation, environmental sustainability and impact on the local community are not the only achievements. What also differentiates it in the judges’ eyes is that the project’s forward-thinking design decisions have had a far-reaching influence. Training for women was a direct result, as was boosting the use of earth as a building material rather than concrete. The fact that RICA has hosted VIPs from other countries looking to replicate this is a testament to that.

View the IStructE 2024 Award winners at b.link/IStructE_awards2024

Image credit | James Kitchin