Missing link

Construction verification - the missing link

When it comes to addressing gaps in the BIM chain, it’s time to take a look at construction verification as a way to add long-term project value, says Michael Johnson, a senior BIM consultant with chartered surveyors Plowman Craven

From the introduction of CAD in cial, providing a great new data tool to Using this new workflow while workthe late 1970s to the latest inno- validate the accuracy of recently complet- ing on some of London’s landmark buildvations in BIM, I’ve spent the ed work against the construction PIM. ings has enabled the team at Plowman last 35 years following the As hardware, software and processes Craven to identify the critical stages development curve and uptake of digital become more advanced and better under- where construction verification adds workflows. stood, construction verification will long-term project value. Our conclusion

And as senior BIM consultant at lead- become a vital tool in delivering against is that it really does have the potential to ing chartered surveyors Plowman increasingly stringent client requirements. change the way projects large and small Craven, one of the most technically inno- With large construction projects are executed, reducing risk and potentialvative companies in the field, I have a increasingly using a PAS 1192-specified ly saving millions of pounds in change personal interest in ensuring that invest- BIM that demands LOD500 or an ‘as- orders and costly reworks. ments in BIM made by clients and their built model’ of the completed facility, the In addition to clients viewing construcdelivery teams have real-world value use of laser scanning in construction is tion certification as a kind of ‘insurance throughout the design, build and manage already exploding. We see construction policy’ against potential variation claims, stages of an asset’s lifecycle. verification as a great opportunity to con- we are witnessing an increase in the

It strikes me that, despite the great tribute to an industry-wide improvement number of developer and end-user clients advances that are being made in the use in standards, efficiencies and cost savings. who see it as a method of proving conforof PAS-1192, federated models mance to contractual tolerance and LOD/LOI, the fact remains that, in most cases, BIM could be said to stop when the first ‘‘ Many still see BIM as existing only set by the design teams. It’s also a way to avoid duplication of work caused by multiple substeel is erected. inside a computer or, at best, as a contractors commissioning sur-

The reason for that, I feel, is federated model supporting 4D and 5D veys to validate the work, prothat many still see BIM as existing only inside a computer or, at processes. This needs to change duce as-builts or check defined tolerances. best, as a federated model sup porting 4D and 5D processes. - ’’ As BIM Level 3 moves from its current embryonic form to a

This needs to change. As the industry In addition to monitoring construction better developed, more clearly defined continues to improve its understanding of progress against programme milestones, tool, data and verification will play an where and how BIM can help to improve construction verification – if carried out increasingly important part in our future design coordination and identify poten- at pre-planned construction stages – deliveries. Dr Ioannis Brilakis, a lecturer tial issues before construction starts, the could assist the supply chain in discharg- at the Laing O’Rourke Centre for real challenge we now face lies in auditing ing some of its responsibilities surround- Construction Engineering at Cambridge and recording exactly what has been con- ing ‘as-installed’ model data. University, has aptly described the next structed against what was designed. I’m convinced, in fact, that construc- level of BIM as ‘as-is BIM’.

But that raises an important question. tion verification can play a significant From a contractor’s perspective, the In addition to demonstrating that con- role in the early recognition and subse- not-too-distant future may involve checktractual obligations have been met, what quent mitigation of some of the ever- ing construction methodology using realmight be the other commercial advantag- present and costly delays, re-works, time information, supported by active es of having documented, independent package creep and legal and financial monitoring systems feeding data back certification of the positional accuracy issues that blight our current processes. into live models. and content of installations? It might bean obvious question, but what Being a technically-led company, we are

For VDC [Virtual Design Construction] impact might a reduction in contingency constantly looking to improve on accuracy and BIM managers, a construction verifi- have on work-won ratios and tender and automate processes where possible. cation workflow could be hugely benefi- return prices? In line with these goals, we are currently

Above and below Construction verification errors

combining our historic project experience with that of sector software specialists to automate where possible the key activities of ‘capture, verify and report’.

We have recently been involved in a London-based project where the tolerance and position of steel frames were of paramount importance. As such, we were commissioned to carry out construction verification of the steel and concrete packages.

The purpose of the project was to verify that the steelwork construction was within 25mm tolerance of the design, and that it included the penetrations required when federated with the steelwork model.

To achieve the desired outcomes, we laser-scanned and photographed the site and processed the data in Leica Cyclone, before converting the data to an Autodesk ReCap (RCS) file format – and that was the easy part!

The next step required the federation of the point cloud into precisely the same place as the PIM, despite different origins being used in the real world and the model world. In my opinion, we are now – as surveyors – adding real value to money invested in BIM by using the model data to audit reality.

Having reviewed the data within Navisworks, we were confidently able to compile an independent construction verification report, complete with snapshots, descriptions and locations, supported by a TruView visualisation model.

Our client was encouraged by the results and is confident that the early identification of minor differences will be accommodated by agreed design changes – with less impact on a complex construction programme than might have been the case previously.

Another recent example came about when Plowman Craven was commissioned by a leading London developer to assist in the monitoring of complex services as they were installed in a prestigious development in the capital. As each basement construction was completed on the 19-storey building, it was 3D laserscanned and a coordinated comparison made with the structural and services design.

The ability to understand differences or clashes between ‘as built’ and design enabled critical alterations to be made to the design, as well as physical changes to be made on site, both in a timely and cost-effective manner. Ultimately, this led to fewer RFIs and smoother contractor handovers, again proving the tangible benefits of this invaluable process.

■ plowmancraven.co.uk

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