Partnering with a Contractor

How LA Surveys shaved 16 weeks off a construction programme and, in doing so, helped the contractor secure the project.

From survey to BIM model

Role
Working for the contractor, carry out a 3D point cloud survey where the proposed extension is to be built and build an accurate BIM model.

Brief
To ensure the highest level of accuracy so the BIM model itself could be used to place orders for steels and glazing elements, without the need for verification dimensions being taken on site during the works.

Worthy of note
The contractor secured the contract by being able to reduce the construction programme by 16 weeks by relying on the accuracy of our survey and resulting BIM model to size and manufacture the steelwork and glazing before the sub-structure had been built.

The consultation.

The contractor came to us with a question and a proposition: could we guarantee the accuracy of our survey and BIM model sufficiently for them to be able to place orders for key building elements without the need for on-site, post-installation measurements? If we could, they would be able to save 16 weeks on the lead-in time for the glazing.

Not without good reason is this practically unheard of in the construction industry! In normal circumstances, steels would be ordered and the structure built before the resulting “as-built” measurements can be taken from which to confidently order the glazing. A process that can take months.

Because we have complete confidence in our Architect-led measured surveys and their resulting BIM models, we can reduce the risks for clients and help provide them with early cost certainty.  In this case, we were able to provide the necessary reassurances to the contractor, allowing them to put forward a super-competitive programme, which was key to them winning the project.

“Lees Associates’ in-house 3D survey and modelling team assisted us with a challenging glass and slate building connected to an historic brick wall. Very fine tolerances were required… Money well spent! ”

— Ross Bejashvili, Managing Director, Lexi Construction

The survey.

The 3D point cloud measured building survey was carried out in half a day using our state-of-the-art Faro laser scanners. These allow us to scan a space with a high degree of granular precision, with a typical tolerance of just 5mm over a whopping 150m! This level of accuracy was vital for the specific needs of this project.

Prior to the survey, we had identified the locations where the new steelwork would connect with the existing walls. So at these spots, we made sure that the survey was captured super-accurately and translated into a 3D model with the same precision. As Architects, we make sure we understand the outcomes needed from the survey, including the requirements of those who will use it.

We also used the scanners to take measurable 360˚ panoramic photography of where the garden room would be built, meaning no return visits were needed; we captured all the data we would need in one quick visit.

From survey to BIM model

The BIM model.

We used the raw data from the point cloud survey to create a detailed BIM model of the space where the extension would be built. The process itself requires a high degree of technical skill and precision as each point is traced into the BIM model using specialist software and a trained eye. We fully understood the context of the data we were interpreting for the contractor because we were both the surveyors and the architects. This always ensures we have complete confidence in both our survey and our model.

Normal drafting conventions for creating a plan would see it drawn with the walls shown where they are at a height of 1.2m, but this would have been too unreliable for us to coordinate structural steelwork that would be fixed much higher than this. While a wall may look straight to the human eye, in reality, there can be many minute variations which would impact the size of any new structure connecting to it. This is particularly the case in historic buildings, where we often find huge variations in levels, including bulges on walls. Our 3D scan accurately located the walls at all heights so we could build the BIM model to be completely accurate at each and every point the steel structure would make contact with them, whilst also allowing any bowing and projections to be considered. It was crucial that, where the steels connected to the existing structure, the level of detail of these contact points was precise. We were able to provide an exact measurement at each spot which the manufacturers could use with confidence to fabricate the steel and then the glass.

Structure and services coordination

The BIM model also ensured that clashes were easily avoided because our software highlights potential clash points in the model, for example between a steel and a downpipe so that they can be avoided.

The interactive panoramic photos allowed everyone involved in the project, not just us, to access the proposed building site virtually, and to zoom in and out with complete accuracy, which is invaluable when the team are not all in the same place at the same time.

Structural setting out

By making use of our innovative specialist process, the contractor could guarantee that they would save their client 16 weeks on the construction programme compared with their competitors. It was this ultimately that resulted in them winning the prestigious contract.