Should we be designing for deconstruction?

A team of Cambridge researchers are making the case for flexible buildings that can be easily reused and recycled. UK INDEMAND’s Julian Allwood and Danielle Densley Tingley explain the benefits.

Supermarkets in the UK are typically refurbished after 10 years and replaced after 20. The replacement is generally opened on a different site to allow a change of size, and the old store demolished. What if, instead, we built supermarkets out of a prefabricated kit of parts that could be quickly constructed, would be flexible in use and could be dismantled and reused after 20 years?

Researchers at the University of Cambridge spent a year working with a large supermarket chain on this and found that the biggest challenge was developing a reusable floor slab that remained perfectly flat. The proposed prefabricated floor plank system increased overall costs by 16% compared to a conventional store, and the board decided not to pursue the proposal.

However, the faster construction time and flexibility of the system were seen as important commercial benefits. The UK INDEMAND Centre team at Cambridge are now working with temporary construction specialist ES Global to explore how a foundationless, deconstructable steel-framed building system could be adapted to suit the requirements of supermarket construction as well as schools and other commercial buildings.

This ideal of flexible, deconstructable buildings could be extended across many other segments of the building stock. It would require some changes in design with existing building components, particularly related to the floor slab or foundations, and could be achieved if adaptability and deconstructability were incorporated into project briefs and embedded at an early design stage. The result would be buildings with longer lives and far greater material reuse than is currently possible. The benefits include a significant reduction in embodied emissions, reduced waste, increased adaptability and faster construction times.

This shift to reconfigurable design would place greater value on the materials within the UK’s building stocks. Around 54% of steel and almost all cement – accounting for 32.5% of global industrial emissions – is used in the built environment, so reducing demand for new production of these energy intensive materials could contribute significantly to emissions reduction targets.

Previous research at Cambridge has demonstrated that the mass of structural steel in multi-storey construction could be reduced by almost 50% and still meet the Eurocode safety standards: design contracts are currently placed separately from material purchasing, so designers are motivated to complete a safe design rapidly rather than to create an efficient design that meets the Eurocodes without exceeding them.

In addition, if buildings were designed with future users in mind, incorporating flexibility and adaptability into their designs to allow subsequent alteration and upgrade, their useful life could be increased from the current average of 40 years to 100 years.

When these two measures are combined for commercial buildings we could reduce embodied emissions by 80%, meeting the target from the 2008 Climate Change Act with no technology innovation or loss of value to users. Design for adaptability is based on a series of principles, including:

• Designing in layers, so that the structure, services and facade are separate and the individual layers can be changed or upgraded without damage to the other layers.
• Ensuring that components with the shortest lifespan are easily accessible to facilitate maintenance and replacement. In particular, ensuring easy upgrade to services and insulation increases opportunities to reduce operational carbon emissions for the building throughout a longer life.
• Incorporating design for deconstruction into the whole building plan enables the addition or removal of sections of the building as space requirements change.
• Designing longer clear spans with larger ceiling heights, and providing some excess capacity in vertical columns increases the options for future reconfiguration, changes of use and the addition of future services, even though this may incur a small increase in initial material requirements.

The strategies of design for adaptability are largely parallel to those when designing for deconstruction. This has an additional benefit of being a built-in fail safe: if the building is no longer required then it can be deconstructed and either moved to a new suitable location, or the individual components reused within new construction. This thus preserves the value of the materials and the embodied carbon already expended in creating them. Steel frame fabricator Portal Power, a business operating in Suffolk, has for 30 years provided this service for single-storey portal frame buildings, and is a growing business.

The UK INDEMAND Centre is now collaborating with the Alliance for Sustainable Building Products’ RE-Fab project team to build on this experience and develop a framework that quantifies the deconstruction and reuse potential of new buildings with a wider range of forms. This goes hand in hand with demonstrating the business case for deconstructable buildings. The more buildings designed in this manner then the more successful the strategy is shown to be, creating a larger pool of future reusable materials.

To be most effective, these strategies must be applied at an early design stage and will be successful with a coordinated approach from the design team. Our researchers are tracking projects through the design stages to highlight opportunities, gain a better understanding of current barriers and estimate the impact on building costs.

Dr Julian Allwood is director of UK INDEMAND and Dr Danielle Densley Tingley leads the construction team for the Cambridge centre. If you’re interested in working with them to develop pioneering case studies, please email [email protected]