How the first BIM project in social housing could provide a model for the future

But what is this new technology and why is it a game changer? BIM builds computerised 3D models of buildings. Rather than relying on 2D drawings and printouts, a single digital model is used by everybody during the pre-construction phase. This does away with all the to-ing and fro-ing of documents and information between the various parties involved – architects, builders, structural engineers, plumbers, and so on. Crucially, the models are not just representations of a building’s spatial form; they are also shared, centralised repositories of data on every aspect of its fabric and features.

“When you click on a window in the 3D model, it gives you loads of parameters – height, width, fire ratings, warranties,” says Patrick King, head of BIM technologies at ECD Architects. “Same with a wall: the paint finish, how many coats, its acoustic rating, whether it’s timber framed – any information you want.”

This information can feed directly into asset management systems, allowing managers to access data on the lifespan, warranty, make and model of any aspect of a building (see box: How long does it take to change a light bulb?).

BIM’s cheerleaders claim that it will change every aspect of building and managing homes for the better, all the way from a project’s conception to the end of its life cycle. Done right, BIM can save time and money, while delivering better quality housing and making residents happier.

It sounds like a no-brainer, especially for a cash-strapped housing sector. But housing has been slow on the uptake. BIM technology has been used in the wider construction sector for years. Could this modest scheme in Nottingham represent a turning point for housing?

Richard Whittaker, head of regeneration at NCH, talks about BIM with the zeal of a religious convert. He first began to consider it seriously, he says, following a meeting with other construction professionals at which a Ministry of Defence project manager claimed to have saved millions on an undisclosed project by using BIM to reduce the height of a building by half a metre. “We agreed to trial it,” Mr Whittaker says.

The Meadows, he claims, has been a tremendous success. On a per-unit basis it cost almost 5% less than Cranwell Road, and Mr Whittaker says it is the cheapest scheme NCH has ever built. To understand how this was realised, it’s worth looking at the scheme through each of the major stages of its development.

Improving accuracy

Designing the building using BIM meant fewer expensive corrections had to be made on site, once construction had begun. “We have had schemes designed previously that didn’t fit on the land available,“ Mr Whittaker recalls. “We had one where the last house in a row finished on the pavement because the measurements were wrong – there was no way of telling that because they were all on separate bits of paper.”

A BIM model, by comparison, allows designers to make sure everything fits and functions correctly before a spade even goes into the ground. The system features something called clash detection so if, for example, a gas pipe runs through a steel beam, or a boiler flue doesn’t have the necessary clearance, the model will flag these up long before they become costly nuisances in the physical world.

“We’ve got 5,000 people on the housing waiting list in Nottingham. We have to deliver at speed.”

BIM models also provide accurate materials schedules. Users can calculate the amount needed – of everything from bricks to doorknobs – for a particular project, and the system updates these amounts instantly as changes are made to the design.

The Meadows is the first social housing built using BIM technology

“So when it comes to tender, once you’ve signed your models off you know your measurements are right – window sizes, door sizes, quantities,” says Mr Whittaker. The difference in price between the first and second place tenders for The Meadows, he says, was just under 2%. Traditionally that figure would be upwards of 3%.

“On a job that size, it’s a fantastic result in terms of cost certainty,” he adds. In turn, that gave him the confidence to halve the size of the development’s contingency fund from 10% to 5%. “We spent 4.9% of the contingency [on The Meadows],” he says. “On the traditional site, I spent 9% of the contingency. These were pretty similar jobs [so] that is a real success.”

Constructing these models might be a highly skilled exercise, but viewing them is as easy as playing Minecraft – and in Nottingham, that proved a real boon. At the consultations NCH held about The Meadows prior to starting construction, visitors were able to walk through the model themselves using an iPad. “People had wanted to move out because they didn’t like the area,” Mr Whittaker says. “When we brought along the model, and walked people through it, people started coming back to us.”

He tells a story about another planned BIM-led NCH scheme to refurbish two existing tower blocks and build a new extra care scheme in between them. On a walk through the 3D model of the refurbished block, one resident looked out of her window and noticed that the new building would have blocked her view.

“So we moved the building a metre to the right and a metre backwards and it solved that issue,” says Mr Whittaker. “It looked OK on the drawings, but of course they were 2D.”

All hands on deck

It’s hard to find a downside. The wider construction industry seems to have got the message; a survey by NBS, a BIM services provider and subsidiary of the Royal Institute of British Architects, last year found that 54% of its respondents were now using BIM on at least some of their projects. So why has it taken so long to catch on in housing? The Homes and Communities Agency (HCA) doesn’t know how many developments it funds that use BIM, but there are relatively few that have mentioned anything publicly.