Powerful modern technology and historic buildings can make a successful partnership
Are the highly decorated buildings of the past too complex to benefit from the advantages of building information modelling? BIM is a powerful technique that should be useful across the lifespan of a building. It’s a resource that’s too good to lose on a project.
First, though, where do you start? Historically, buildings have been better and more accurately described in drawings rather than words and BIM is an extension of that process, particularly for existing stock. Where 2D CAD improved on paper drawings by adding the ability to describe a building in layers, BIM allows the process to be taken further.
So you start by getting your model built up from scratch, either by elevating 2D CAD surveys or getting a cloud laser scan. A full cloud laser scan supported by attached digital photography gives a sound basic record of the building. However, no survey system is a silver bullet – each will need interpreting to be a useful practical tool.
Cloud laser scan gives a line of sight paint skin, a 3D surface model. Translating this into a 3D building model requires judgements to be made about what is under the skin.
Intelligent object recognition
One of the problems – and so costs – with using BIM models for ornate historic buildings is the lack of families of components for doors, windows, mouldings, fireplaces etc. Often, building these up to any useful level of detail will take more time than the rest of the model put together. Emerging software, generally described as intelligent object recognition, may help with this.
Some survey companies offer intelligent object recognition, but there are questions of liability. Architects working with existing stock, particularly historic or heritage buildings, have always done this. Measuring a building and interpreting the results is a very sound way of understanding the fabric, particularly when there are a number of construction phases and significant alteration.
Incorporating evidence from historic drawings is a good starting point. The model is also a good place to record discoveries made when soft stripping a building, opening it up and working on the fabric.
Useful as BIM is for the design team, if it is to become widely accepted the real benefit must come after construction
Phasing (REVIT models) can be used to put elements of the construction into date bands. This is an extremely effective tool when expanding your understanding of a building and is usually a preliminary to sensitivity analysis.
It is also possible to link the model to external data such as a conservation management plan and to specific elements such as the room gazetteer, not just as a reference but also to enable display of say sensitivity analysis directly in the model for all users to see. This saves them the time and trouble of resorting to external references when looking at or working on culturally important parts of the fabric, and will also show where the less sensitive elements are.
Room by room analysis can be expanded to highlight particular features in each, such as a fire surround, which may have individual sensitivity or significance that is different to the rest of the space.
Filling a gap
There is much to explore in discovering what meta data can easily and usefully be attached to the model and in keeping track of how and when it is used, and by whom. The meta data might be used to show the expected lifecycle of major construction elements such as the roof covering, and to record, based on quinquennial or condition surveys, where the element is in its lifecycle and how long before it may be expected to require major repair or renewal. This sort of information will help both the design team and the facilities managers (FM) and users, and would fill a large gap in the advice notes issued regarding historic buildings.
Such analysis can be used for buildings in their passive phase (when maintenance and repair are normal rather than major works, which typically happen on a 25 to 60 year cycle) and can be used to build up a system of programmed maintenance. A 3D model will assist in one of the major considerations when setting out programmed maintenance on large buildings; this is that the cost of access, particularly when scaffolding is required, tends to determine what work is done when. Any technique that can improve the value achieved from gaining access must help to reduce running costs and surprises.
BIM models generally need better trained and more self-disciplined operatives than many design and FM teams can offer. At present owners and untrained users are unlikely to be able to use them easily, even when they are part of a large organisation. It will take time to build the skill sets and experience needed to get the best out of BIM. Some users have made the leap but in the historic buildings sector in particular it seems likely to be a slow process.
Useful as BIM is for the design team, if it is to become widely accepted the real benefit must come in RIBA Work Stages 6 and 7 – both in passing on the knowledge and information acquired by the design and construction teams and in providing a useful tool for managing the building in use.
The model should be kept live and either needs to incorporate FM management in the design software or to link to established FM software packages.
Clients need to be aware of what the design team will be delivering and be ready to make use of it, otherwise many of the long term benefits will not be realised. Architects could offer holding and managing the model as a Stage 7 service. This could be linked to specialist conservation consultancy, specifically by making routine reports such as quadrennial and quinquennial inspections linked in to the BIM model.
BIM offers some powerful tools and techniques for those working with existing buildings, particularly those which are regarded as heritage assets. The HBIM label (historic building information modelling) rather misses the point. Building physics and the laws of gravity, for instance, are no different for historic buildings, and nor should BIM be seen as different for existing buildings rather than new.
Existing buildings, particularly complex and ornate constructions, are more difficult and more expensive to model accurately than when assembling a model of a new building from current component families, but as long as this initial overhead is recognised at Stage 0, and enough time and resources are allocated for developing the model as existing, the long term benefits should be considerable.