6 week research trip in North America exploring deconstruction practise and timber reuse. The research had two aims:
- To learn about structural reuse of timber; and
- To learn about deconstruction practise supplying timber for reuse.
It was a fantastic opportunity to explore a growing industry and approach to building removal and meet a collection of welcoming, hospitable and knowledgeable people passionate about these topics.
I’m currently looking for opportunities to take the research further – particularly with developing economic methods of regrading used timber for use in value added engineered wood products such as glulam/crosslam. Please get in touch at email@example.com
Structural engineering is a game of resource management. Our role is to complete a task within a set of constraints: what a structure needs to do, where it needs to do it, and what resources we have available to make it. A structure’s role and location are defined, and while we cannot influence available resources like time and money, we do have influence over the available material resources. When a building is removed, there is a choice in the method of removal, determining how useful the building components will be post-removal. The usefulness potential of a material resource can be indicated by the entropy in a system, with lower entropy systems having a concentrated useful energy than higher entropy systems that have dispersed their useful energy.
An unwanted building has an associated level of entropy: it has individual components maintained in an ordered system. When the building is demolished its entropy increases: its individual components are broken into smaller elements, and the system as a whole becomes disordered. Useful energy has been dispersed in the building removal process. However when a building is deconstructed the individual components remain unbroken while the system is disassembled and reordered; less useful energy has been dispersed in the building removal process.
Energy is an indicator of successful resource management. Using more of it comes at financial and environmental cost. Building deconstruction allows us to expend less energy than building demolition, and better able to manage the material resources that they contain. Deconstruction leaves low entropy building elements, like a steel beam, which are ready to be reused immediately with little input of useful energy. Demolition leaves higher entropy building elements, like a bent and distorted steel beam, that require an input of useful energy to reprocess and recycle them.
Why reuse timber structurally?
Buildings are removed for any number of reasons, whether they are structurally unsound, undesirable, or uneconomic. If a building’s constituent parts perform their role sufficiently in an existing building, there is no reason why they would not be suitable for use as part of an alternative new structure.
Of the three primary construction materials used today in the UK wood is the least prevalent. However structural timber is the fastest growing commercial construction method in the UK, and 25% of all new UK homes are built with timber frames.i While improvements have been made in construction and demolition (C&D) waste management of concrete and steel, timber waste management has not progressed as far. Data has indicated that in recent years in the UK nearly 60% of C&D wood waste went to landfill. Similar proportions of wood waste going to landfill can be seen in the US. In Vancouver wood waste is the largest component of demolition, construction and renovation waste making up 58% of landfill.
The wood product life-cycle illustrates the increase in entropy of wood as it is processed, and the additional energy inputs required to make these product transformations. To maximise the use of the resource against the energy input, the wood product should be maintained at the lower entropy end of the life-cycle for as long as possible. Reusing wood can reduce the stress on our forests by minimising the requirement for logging, as well as encapsulating embodied carbon for longer.
Studies have indicated that reductions in environmental impact can be made simply by reusing old timber elements in new construction. With the growth in the use of structural timber in UK construction, this could become an increasingly relevant margin over the coming years.
In 2011 there were an estimated 78,000 abandoned homes in Detroit, the city’s population having shrunk by more than 25% between 2000 and 2013, and more than 60% from its 1950s peak. This population loss falls within a context where Detroit has low land values and levels of high school education, and high unemployment rates.
Faced with ghost neighbours and associated high levels of crime, the Detroit Blight Removal Taskforce, Detroit Land Bank and the Mayor have mobilised funding from the federal Hardest Hit fund to develop a mass land redevelopment scheme to remove the city’s blight. It is estimated that 4,000 buildings are being removed each year; a rate which is visible across the city. While the majority of these building removals are demolition, the combination of the political will, low housing value, unskilled workers and high unemployment rates have made Detroit a unique testing bed for the success of deconstruction schemes.
The vernacular architecture in the Great Lakes area of the US for single family residences is timber construction, partly due to the extensive forestry resources of North America. Indeed timber construction has been the prevailing house-building technique for over a century, using the primeval forestry resources that were present on the continent when European colonisation began. Consequently much of the housing stock that is now being removed was built from forests and trees that are no longer available, such as large diameter trees with tight-grained dense wood which is stronger and dimensionally more stable than new growth wood, and highly aesthetically prized.
This abundance of timber in the building removal waste stream, and the high quality of much of it, makes the reuse of deconstructed timber in Detroit and the Great Lakes particularly pertinent.
Current economic trends in the developed world are seeing migration from industrial and manufacturing regions to service industry urban centres. This pattern is creating a high housing demand in some areas while leaving buildings derelict in others. In response urban areas are regenerating abandoned substandard housing stock, both to meet demand in growing communities and to stabilise shrinking ones.
Detroit can be a bell-weather for post-industrial urban areas – a template for cities facing similar issues. Comparisons can be drawn with Clevelend, Buffalo, Gary, Peoria, and Baltimore, where building deconstruction is also undertaken. The processes of tackling post-industrialisation and community contraction in the US can be compared to the demise of the coal-fields and manufacturing heartlands of the North of England in the 80s. Yet building deconstruction and timber reuse do not need to be confined to post-industrial communities – while much differs between the Rust Belt and London, aspects of the lessons learnt could be effectively applied to urban renewal in cities undergoing conventional redevelopments.
Raleigh / NC
- Attendance at DECON’16, hosting charrette Crossing the Atlantic with Dave Bennink of Re-use Consulting
- Meet with Blueridge Timberwrights
Toronto / ON
- Meet with Tim Krahn et al
Detroit / MI
- Tour warehouse and deconstruction sites of Architectural Salvage Warehouse of Detroit
- Meet with Workshop, Recycle Detroit and Detroit Future City
Chicago / IL
- Meet with BMRA and Evanston Rebuilding Warehouse to discuss educational training programs with designers and practitioners
- Visit USACE CERL to discuss deconstruction policy and barracks reuse
- Visit Trillium Dell Timberworks to discuss reclaimed timber testing and regrading
Madison / WI
- Visit the USDA FPL to discuss regrading deconstructed wood products and the implications of their reuse.
IStructE Educational Trust Pai Lin Li Travel Award