Tom Shaw, Director at Ramboll argues that developing brownfield sites for housing can contribute to the quality of existing urban areas and the wellbeing of its inhabitants…
Nearly every week we see media reports on the UK housing crisis, and meeting the country’s needs during its current growth spurt is creating widespread pressure on our resources. The London Mayor’s Design Advisory Group recently launched a report entitled the ‘Good Growth Agenda’, highlighting both a requirement for densification and the fact that, since 2006, 90% of London’s annual housing development has been on brownfield land. With figures like this it’s not surprising that brownfield sites are not only getting smaller, but they are getting increasingly complex to build on as there are a limited number of firms able and willing to build on constrained sites. Therefore, this year’s release of a register of publicly-owned land in London, which highlights 40,000 sites said to be capable of delivering a minimum of 130,000 homes, should be central in driving better utilisation of brownfield land. The land is there, we just need to work out how best to build on it.
The challenge of smaller brownfield sites
Relaxed planning requirements, priority over other developments, and reduced S106 requirements and levies, are all measures adopted to encourage small and medium developers to pick up these smaller and more complex sites. As a result of the fact larger sites have typically already been or are being developed by larger firms, invaluable experience of working on complex and constrained brownfield sites is not as established within smaller firms, so for many it can be a daunting prospect.
One of the main challenges of working with a brownfield site is dealing with the constraints imposed by the site and its previous uses. This can be in a number of forms including; contamination, obstructions in the ground, historic structures, archaeological remains, existing site infrastructure and utilities that may need to be retained or rerouted, and interfaces with adjacent properties and site boundaries. Often these sites have remained undeveloped due to the constraints on the site that may impose complications or push costs too high.
In order to make a site economically viable when dealing with these issues, in many cases the only option for development on a brownfield site is to densify the project – and often this means to build up. For example at present there are 33 developments in the pipeline for London that feature density levels of over 1,000 units per hectare1 which in itself can be controversial as people oppose the imposition on views and sightlines.
Why tackle smaller brownfield land when greenbelt is available?
So if these sites are so difficult, why should we bother with them? Brownfield versus greenfield is a hot topic at the moment, with much debate on whether areas designated as greenbelt should be declassified to allow for development. In some cases, such as the favoured press example of land around Central Line stations in Essex, or other mostly urban areas in close proximity to transport links, then this could certainly be a valid argument.
However, there are a number of reasons why there should be a “brownfield first” policy. Development of brownfield sites brings back to use derelict and underused land, contributes to the quality of existing urban areas and the wellbeing of its inhabitants and minimises requirements for construction on green field or greenbelt sites.
Unlocking brownfield sites
Traditional methods of construction can be cost prohibitive on brownfield sites, and is made worse by the current market in which subcontractor costs are escalating due to a lack of availability. In looking to overcome this we must simplify construction works and aim to provide cost-effective solutions. This could involve regularising layouts and grids to provide flexibility internally, or stacking apartment layouts to avoid additional costly transfers in the building structure or building services. To encourage more self-build projects, ‘off the shelf’ solutions can be developed that allow simplified and cost effective solutions across a number of sites. These could be in the form of solutions that make use of offsite manufacture – also known as ‘Design for Manufacture and Assembly’ (DfMA) – such as cross-laminated timber, steel volumetric pods or precast concrete solutions. Developers are provided with a simple kit of parts that allow faster construction and delivery of projects.
Often DfMA options are overlooked as like-for-like material costs can sometimes be more than traditional forms of construction. However, these materials and approaches need to be assessed in the round, since savings are often possible when assessing the bigger picture. Significant reduction in programme overheads can save on contractor costs, reduce site waste, and enable other elements to be incorporated into the prefabricated components. DfMA structural systems are also often more lightweight than traditional forms of construction, which can reduce foundation size and minimise the amount of work in the ground – reducing risks of ground obstructions and contamination for brownfield sites. These proprietary systems could be developed to allow for flexibility, enabling residents to easily adapt layouts or expand as needs change.
Smaller brownfield sites should not be consigned to the ‘too difficult’ box, as the recent register shows they have incredible potential to aid the UK in tackling the housing crisis – without running the gauntlet of out of town relocation. By adopting alternative solutions and methods of construction, and encouraging small and medium developers and contractors to take on this challenge, we can unlock the value of these sites and tap into the vital community resource that brownfield sites offer.
1 London Development Database 2004/5 to 2014/15, London, Greater London Authority, 2015
Tom Shaw
Director
Ramboll
Tel: +44 (0)20 7631 5291
london@ramboll.co.uk