Damien Campbell-Bell, Geomatics Officer at Wessex Archaeology examines the role BIM can play in built heritage projects, and the challenges it can present…
Our previous articles have given an overview of BIM and Archaeology and discussed infrastructure specifically. In our final article, we look at the application of BIM to built heritage projects. While more closely related to common uses of BIM, its application to built heritage still raises interesting challenges which need to be addressed.
Digital Built Britain asserted that 90% of the buildings in use over the next 25 years already exist. This ageing building stock will mean increasing demand for refurbishment to meet modern needs; sometimes involving structures with complex planning, management and/or maintenance requirements. Projects with heritage elements will range from nationally important Grade I listed buildings, such as the Palace of Westminster, to unlisted buildings which nonetheless are considered to have some level of cultural significance.
BIM and Heritage Management
As with infrastructure, the focus here is on management, and the same benefits apply. It is not just project management, however, but also asset management where archaeologists have a role to play. The principle that only information of use in management is included in the BIM still applies; it should still not be used as a method of preservation by record. There will necessarily be much more data about the heritage asset to facilitate this, however.
The aim of incorporating heritage data into the BIM model is to increase its usefulness. At the moment the norm is for this data, which is of use throughout a building’s lifecycle, to be delivered as a paper report. This makes it easy for information to be missed and leads to double handling if it is to be put to best use. Handling this data better would lead to improved project outcomes and reduce ongoing costs of managing sensitive sites, which may require, for example, regular conservation work. Because of this, English Heritage has expressed interest in using BIM for Facilities Management. By delivering the data usually found in reports in an interoperable format, readable by the clients FM software, it can be used to better manage historic buildings with their complex needs.
This heritage data is also important for planning refurbishments, where certain elements or even entire sections of a building may need to be preserved in situ, or recorded in detail before modification. Understanding a building through a Heritage Statement can lead to clearer planning conditions, but the incorporation of both of these into BIM at the design phase can lead to better, more sensitive designs, which ultimately lead to fewer delays and complications further down the line, due to a failure to fully understand this information. Clashes of geometry and schedule are regularly considered, but in the refurbishment of an historic building, the impact of detailed planning conditions also needs to be considered.
A basic heritage BIM model incorporating data from a Heritage Statement for building sections
Modelling for heritage
The application of BIM to built heritage doesn’t require a major change in archaeological field practice; it is the presentation of the data which needs to change. However, this is not entirely straight forward. As heritage has not been considered in the development of BIM standards, there are no standardised data structures; COBie does not have fields for this data, and IFC’s standard properties do not include it. While the latter can have custom attributes added, this increases problems with interoperability. There are also no recognised procedures for the use of BIM in heritage projects, meaning that if it is to be used, a company must establish their own specification. For internal use, this is less of an issue, but as other contractors, such as conservators, start to use this data or it is incorporated into FM software, this becomes a major concern. To get the maximum benefit from BIM, this needs to change. Wessex Archaeology is running BIM projects in an attempt to establish best practice as a first step towards this.
A further issue with the use of BIM in historic buildings is accuracy; while modern buildings may be made primarily of straight lines and regular shapes, historic buildings are often very irregular. Modelling them accurately, therefore, takes a very long time and involves either creating very complicated elements or subdividing them. For most projects we, therefore, recommend a relatively low Level of Detail, it is after all the attached information which is the key aspect here. For metrically accurate data on existing conditions, laser scan data is far more appropriate than even the most detailed BIM model.
This series of articles has aimed to show that archaeologists have a lot to offer the BIM process, but there is still work to be done across the construction industry to ensure that the maximum benefit from their engagement can be achieved. Once again we invite you to get in touch if you would like to be involved in our push towards the standardisation of Heritage BIM.
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