Residential developer catches the BIM boat

• Client: Telford Homes
• BIM Tools: Autodesk Revit

Telford Homes’ technical director Mark Duffield admits that he didn’t have particularly high hopes for the company’s first foray into BIM. But although the developer isn’t directly involved in public sector projects, Duffield didn’t want to miss the BIM boat. “We decided to dip a toe in the water to see what it was about. We honestly didn’t know where it was going to go, but we thought we could always fall down to a 2D version and play catch-up if it didn’t work out.”

Duffield decided to run a test project on Tweed House, a development of 115 apartments next to the Blackwall Tunnel’s northern approach. Telford Homes had no in-house expertise, so Duffield put together a lead consultant team that had already been using the 3D design software for some time: architect Saunders and structural engineer Conisbee. Finding a BIM-ready M&E consultant was more difficult. In the end, Duffield appointed Waterstone Design, which worked outside the process in 2D.

Rather than sharing a single model, the architect and engineer each worked on separate 3D models which were merged each Friday so that clashes could be detected, then separated again so that the two firms could continue their work over the following week. Duffield attributes the success of the project partly down to the lead consultants’ positive, can-do attitude, but he can see that aspects of the relationship will need to be formalised as BIM hits the mainstream.

The sales team used the BIM model to create marketing materials to assist off-plan sales

“There were never any squabbles about who owned the model, but I’m a little bit wiser now and I can see that there could be a conflict over PI insurance,” says Duffield. “I’m sure there’ll come a time when we put models into the cloud and everybody contributes. The problem is, if everybody can work on it, everybody can mess it up. In a combined model, who has the overall responsibility for a detail that was contributed to by three or four disciplines? It’s a very fundamental thing that needs to be sorted from day one.” To this end, he is working with Saunders and Conisbee on a separate project to establish a bespoke BIM protocol.

On Tweed House, the team narrowly missed achieving Level 2 BIM, as defined by the Bew-Richards implementation model. “We like to think it was level one-and-a-half,” says Duffield. In fact, the only thing they didn’t do was embed facilities management information into the model, because it made it too large to comfortably navigate and share – a technological limitation that he expects to be quickly overcome as computing power increases.

The same team is now halfway through a second BIM project for a much smaller development of 16 units. This time, they are going to export the model as a 3D PDF and label each component with a hyperlink to further information for future maintenance teams. There is the risk that URLs will change in the future, but the additional step of taking and storing snapshots of current websites would increase the demand for storage and processing power.

Even without the FM dimension, Duffield’s team discovered a number of advantages to using BIM. The overall design programme was the same length, but the pattern of information emerging was very different. If a graph of the traditional 2D process looks like a straight line rising at a 45 degree angle, with BIM it is more like a very steep S-curve – nothing emerges for a month or so, then the line shoots up almost vertically before levelling off again.

The earlier availability of detailed information meant that procurement could get underway sooner – once the foundation package has gone out, nothing further is required for three or four months, Duffield points out, “so the design comes off the critical path at that point”.

The trades stuck remarkably closely to the model of the plant room

One of the pleasant surprises was the ease of which they could interrogate the model for quantities of materials such as rebar or bricks, and at their accuracy, to within a single-figure percentage. The cladding contractor also used the model to set out the composite panels on the building’s facade and produce a cut list for the supplier. “All of them fitted first time. You expect 15% wastage with a system like that, but the only wastage we had was breakage,” says Duffield

BIM wasn’t used on site – “there was nobody standing there with an iPad” – but the design team did produce plans and visualisations from the model to guide the trades.

Some of the site team were apparently nervous at the prospect of a new way of working, but Duffield says the information that they received was exactly the same, except that there was more of it. “They could ask the consultants to take a slice of the model or enhance a detail if they weren’t sure what was happening. It was a very useful tool for showing the contractor and subcontractors what they need to achieve. It’s amazing how many people in the industry look at a drawing and don’t see what it will look like at the end of the day.”

One of the best examples is the plant room, where the M&E subcontractor printed out large-scale visualisations from the model and hung them on the wall. Rather than arranging pieces in order of size from the middle outwards until they were boxed into a corner, the trades stuck remarkably closely to the model, as photos of the completed room show (see pictures).

Meanwhile, the sales team used the BIM model to create marketing materials to assist off-plan sales, rather than commissioning an external agency to build a 3D model from working drawings. This not only saved money, but the time that would usually be spent checking the externally-produced model for accuracy. 

The big question is whether BIM actually saved any money on the build itself. He may not have any hard evidence, but Duffield thinks it does make a difference. “There are hidden savings within the process. I’m sure that when we push it up to BIM level 2 and 3 there will be savings. I certainly see BIM as the way forward for everybody – I can’t see anybody not doing it. It is a giant step forward.”