The idea of Earth Blocks came into Bennetts Associates Architect Nikolay Shahpazov's mind back when he spent time in rural Devon.
He quickly recognised that earth construction would perhaps be the truly the 'greenest' ways of building. What started as a side project materialised when Nikolay joined Bennetts Associates. Himself and others from the Bennetts Associates' dedicated sustainability group continued with the research of Earth Blocks to find out how it could be incorporated into the practice's projects. As well as being the focal point of our art work for this year's RA's summer architecture exhibition, Nikolay spoke to Cecilia Lindstrom for The Journal to learn more about the benefits of unfired earth blocks.
Tribeca will be the first building of its scale to utilise site subsoil as a construction material and with the collaboration with Reef group and H.G. Matthews in hopes to set a pioneering precedent on using Earth Blocks for the construction industry.
Earth blocks use excavated clay from the construction site mixed with sand and straw to produce unfired bricks for the new development. Unlike standard blockwork, which has limited recycling potential, earth blocks can be broken down and reused, or returned to nature at the end of their lifespan.
As such, the earth block can store the building resource within the walls of the development throughout the lifetime of the building. This living material also brings climatic benefits to buildings – it regulates indoor temperature and humidity levels, and purifies the air by trapping airborne pollutants.
The project is targeting very high BREEAM scores and various other certifications, but the earth blocks brings another dimension to this ambition, because most of the current sustainability certifications don’t necessarily deal with the embodied carbon of materials. Earth blocks has one tenth of the embodied carbon of other commonly specified materials such as blockwork, which is a cement-based product.
Aside from the high energy demand during production, blockwork and concrete manufacturing consumes large quantities of sand, which has led to fast depleting sand supplies and environmentally damaging sea extraction. The low embodied carbon of earth blocks is a great starting point that positions us ahead of what most commercial developments are committing to right now.
We sample the soil in various corners of the site and test this as an earth block mix with HG Matthews, the material manufacturer. Sometimes the excavated material can be contaminated and require treatment, but the soil is pure deep underground even on previously developed land. The deeper strata of the King’s Cross soil is very stiff clay that produces very strong earth block. Once the mix is determined the product will be assessed to specify the technical performance before scaling up production. At least 60% of the excavated earth can normally be used, saving the developer expensive land fill tax.
For The Apex, the earth blocks are used exclusively in the basement in place of concrete blockwork. Earth blocks can be used as load bearing elements for smaller buildings, but because they are unfired, they are weaker than blockwork, requiring a different approach to structural engineering.
There are other manufacturing techniques using dynamic compaction that can produce denser blocks almost twice as strong. Austrian earth construction specialist Martin Rauch has developed an automated method of manufacturing off site rammed earth cladding panels that achieve significant carbon reductions. Increasing the strength and usability of the product will unlock more design opportunities and architectural expressions. It is an incredible material with a tactile quality that connects us with the earth and ancient geological processes. I think it is really beautiful.
Alongside our project work, a team from Bennetts Associates has created ‘Earthcycle: Earth blocks from subsoil’ which is currently being exhibited in the 2022 Royal Academy of Arts’ Architecture Summer Exhibition.
Designed together by a from Bennetts Associates team: