BIM will soon be the principal tool for managing historic building projects, writes Buttress Architects’ Grant Prescott
Building information modelling (BIM) technology is well-established and increasingly relevant across the built environment and the capabilities it affords within the heritage sector are developing at pace. As BIM progresses and we integrate ever more information into digital format, it will soon become the principal tool in the management of change – and risk – on historic building projects.
Recent studies such as BIM for Heritage, published by Historic England in July 2017, have highlighted the difference in initial information required between new build schemes and historic buildings. Heritage projects have unique physical fabric that encapsulates the intangible values contributing to its significance. The National Planning Policy Framework rightly focuses on the importance of understanding this significance in the management of change. Current data capture facilities ensure detailed recording, and well-developed Historic BIM can augment understanding. We can use it to underpin proposals, explore potential harmful impacts, provide justifications for new interventions, and operate with the utmost understanding of conservation philosophy.
Example of use of bim in the context of a medieval castle site
Understanding in this context is also supported by the inclination towards collaborative working. Team-wide sharing of information through BIM Level 3 will augment communication between disciplines. It will enhance whole-project understanding of heritage significance, and subsequently produce sensitive and thought-out responses to difficult contexts.
Our experience at Buttress Architects has led us to characterise BIM for historic buildings in two ways: Variable and Static. These terms refer to the purpose and lifespan of the model, though there is definite overlap. Variable models are those created as part of an iterative design process, and for day-to-day facilities management that may require updating at intervals (alongside a conservation plan or after a capital project, for example). Static is mostly associated with single-use models created as building records. It is possible for a baseline BIM to become both static and variable. An unedited model can be used as an archival building record, while a duplicate model expands to encapsulate design development and post-project management. This approach was adopted for the Grade II*-listed First White Cloth Hall, in Leeds. Here, the model (pictured below) has been used to unpick the highly intricate historic phasing to facilitate understanding and inform the conservation plan. Simultaneously, it has underpinned the design process, as an iterative working model.
It is imperative at the beginning of any historic BIM project to identify the needs of the client, and consequently the scope of the brief for the model commission. Key constraints should be identified in the project brief, including the specification for Level of Detail/Level of Information. Historic BIM requires a substantial amount of information to capture physical fabric and abstract values. In conjunction with laser surveys and extracted point cloud data, experience has led us towards the incorporation of analysis from Level 4 building survey information, which we have utilised on internationally significant historic sites. The result is an efficient and thorough working model with an established intended audience.
Variable Historic BIM is particularly effective when adopted alongside a virtual reality consultation approach
We have been able to use these layers of information to fundamentally inform proposed designs on sites of national importance. At Chester Farm, Northamptonshire, we interrogated micro-interventions where new structures interact with Grade II*-listed historic fabric to find the point of minimal harm, while at First White Cloth Hall we have been able to work sensitively within the fabric to develop options. Knowledge means we can present an in-depth and sensitive design solution that meets the needs of the client and the heritage. It has the added benefit of demonstrating an auditable decision process that will provide invaluable support to any heritage impact assessment.
Variable Historic BIM is particularly effective when adopted alongside a virtual reality (VR) consultation approach. There is huge benefit in demonstrating capital project proposals to clients through immersive VR. Clients are able to provide thorough feedback by interacting with the whole space and interrogating specific micro-elements. It’s an intuitive and accessible process, requiring no specialist knowledge or ability to read drawings. With the right set-up, clients, design teams, managers, local councils, international organisations, and members of the public can engage with the process of change in the historic environment.
Phasing model of first white cloth hall, leeds
There is also future scope to create an immersive options appraisal process, where clients can resolve or debate issues by experiencing the space. ‘Can we try a different finish here?’ ‘What about relocating the lift and stair core?’ Though design options can make models unwieldy at present, there is definite scope to present this kind of solution. Overall, it helps to facilitate increased buy-in from stakeholders and smooth the consents and consultation process.
There is also a significant benefit in sharing models online to enhance accessibility for non-technical professionals. For example, clients and consultees can view the whole scheme, examine specific elements, and even take cut-through sections and provide detailed feedback without the need for software literacy and without physically editing the master model. Our software allows us to quickly and easily export information while maintaining the level of detail of the model. In the case of the Church of the Ascension, Salford (devastated by fire in early 2017, pictured top), it is possible to view the interior from eye level and observe in 360˚ the key surviving elements, allowing active engagement in the above processes.
Static BIM models, created either stand-alone or as an early stage of a Variable BIM, have value as digital building records for both day-to-day management and capital projects. The initial model can act as a static existing image of the building before the beginning of any new works or commissions. It can mark a point in time before a building or a project evolves. A client can also define in a brief that they want a model that can be edited to incorporate and identify new works, keeping a record of minor and major change.
If appropriate, these Static BIM models can also become part of a publicly accessible facility, such as a historic environment record or archive repository. It will contain unprecedented amounts of information that can be retained for posterity. Critically, using Historic BIM as a record legacy requires the resolution of various significant challenges. The archive sector has been in discussion about methods of digital preservation for the best part of a decade. Issues around user skills, proprietary software and emulation of hardware or software must be resolved for BIM to be an intelligent and sustainable building record. There are also questions around the compatibility of existing files with future software.
Architects in the heritage sector must advocate a multidisciplinary approach to solving these tricky issues. Historic BIM building records require a thorough infrastructure for the conservation of the information files which is yet to be developed. Despite challenges, the growing appreciation and understanding of Historic BIM is encouraging, and it will continue to transform management of change. It may radicalise the successful and sustainable development of the historic environment – if we invest in its potential.
Grant Prescott is a senior architect at Buttress Architects
This article appeared in the September issue of AJ Specification