Making BIM work for existing buildings


Adding performance data to existing models will save money in the long run, but will clients see the benefits?

As BIM penetrates the way we work on new buildings, teams are starting to become familiar with the process of making information models. As an activity it has many similarities with the way buildings were, and still are, designed when information was distributed across drawings, schedules and specifications instead of in an integrated model from which these views can be extracted.

Fundamentally the process of laying out the spatial brief, and then assessing the performance requirements of walls, floors, doors and other elements and then specifying them still underlies the modelling and data entry and follows the same sequence.

However new buildings account for only a fraction of the building stock, and existing buildings which require existing BIMs are a very different proposition. Everyone in our industry has seen the compelling images of pointcloud surveys that can now make such great records of condition, and these surveys provide the basis for producing geometric models of buildings, at least any bit that you can get sight of with a laser scanner. The accurate geometric information, the ability to refer back to the pointcloud for more detail later, the reduced need for site visits and the completeness of information captured makes the value of this type of survey unquestionable, but the functionality of the model produced is limited.

New buildings account for only a fraction of the building stock, and existing buildings which require existing BIMs are a very different proposition

The problem is that scanners don’t record the performance, specification and lifecycle and other properties of the walls, windows, doors and other systems in the building and it is this information that could make an existing model much more strategically useful in decision making associated with programme and cost.

We have recently produced two large existing school models. As part of the capture we really wanted to get information into the model beyond the geometry and so we scoured the webshare of captured data for fire signage on doors, escape signs, even looking for seals on doors to indicate that they might have some fire or acoustic performance. Of course these can only be offered up as useful observations when collected in this way with a disclaimer that they are what we had been able to see, and as such need to be checked.

So what next? For example, can we agree the performance of existing elements before the designer or constructor starts work? The value of collecting this data and adding it to the federated existing building model is unquestionable. Yet is the cost unpalatable? Adding performance data to existing models is another example of that recurring theme in BIM – spend up front and save tenfold later. Our initial experience with large clients suggest that more forward looking contractors do, and will take the benefits, but will clients and their agents see it that way? History and the lowest cost culture of the UK construction industry suggests perhaps not, but maybe the reduction in risk and the opportunity to re-use existing elements will be a clear enough win.

To my mind this is a perfect example of a strategy that would contribute to the BIM taskgroup’s stated objective to reduce waste in construction by 40%.

First published on 17 October 2013 on