BIM hasn’t been big news in the residential sector. But PRP Architects is showing it does have a role, while Bryden Wood is using it to rewrite the rule book in Russia. Elaine Knutt reports.
In all the current debate about BIM, housing has hardly been front of mind. In the eyes of most clients, BIM is about simplifying the design and construction process in complex buildings, or supporting long-term responsibilities in maintenance and operations. But building a block of flats or a terrace is usually straightforward – and there’s zero ongoing responsibility if you’re building for the private sales market.
But a number of consultancies and contractors are now starting to trial BIM in the residential sector. Design and technology company Bryden Wood, for example, has chalked up a notable UK BIM success story with its appointment to lead a BIM-based project to deliver 15,000 homes in St Petersburg over five years, pursuing an approach that integrates BIM modelling and Design for Manufacture.
“We’ve always been in this patch, but now we’re getting mainstream projects,” says director Jaimie Johnston. As well as St Petersburg, it was recently appointed to design a new £75m pier for Gatwick Airport.
Closer to home, and perhaps to the experience of most in the residential sector, PRP Architects is extending BIM from a designer-only phenomenon to include contractors such as Wates Living Space. “We’re trialling BIM techniques today [at a mixed-tenure block in Stockwell, London] in the hope they become embedded BIM processes tomorrow,” explains director Scott Sanderson. “The early adopters have been pushing BIM, but it’s tended to be quite ‘lonely’. Now, having established that capability, people are ready to collaborate.”
Bryden Wood’s St Petersburg project is a sneak preview of the future if the logic of BIM is fully embraced. Building up an integrated design model that is starting to include cost and procurement data already implies different roles – and perhaps fee structures – for the wider project and construction management led by Mace and including QS Turner & Townsend. As for the designers’ roles, there’s already a clear impact. “It reduces the design effort and focuses on where the design architect can add value. It takes away a lot of the back end stuff, the churning out of working drawings and specification schedules,” says Johnston.
Semi-skilled labour
Once on site, the traditional division of work into discrete specialist packages with critical programme interfaces breaks down – in the BIM and DfM world, the construction site starts to resemble an assembly plant staffed by semi-skilled labour. Bryden Wood has already demonstrated the benefits this approach can bring – at Circle’s Reading hospital, it cut capital costs by 28% and the programme by 20% in relation to the benchmark set by the client’s original scheme in Bath.
In St Petersburg client SPB is developing a 65 ha riverside site situated half an hour by metro from the historic centre. The 15,000-home scheme will be built in 50 blocks, ranging from five to 25 storeys, set in a masterplan by Swedish firm Tovatt that also includes schools, shops and business units. Bryden Wood is lead architectural designer (as well as structural and MEP consultant) setting the design framework within which four other architects – PRP, Aedas, HKR and Semren & Mansson – will design individual blocks.
Certain design parameters have already been fixed: the width of the blocks is set by local regulations on daylighting; the frame will be constructed from a mix of precast concrete beams, in-situ concrete and steel. All connections will be at waist height for safety and speed of assembly; and corridor sections will accommodate horizontal services in compartments at ceiling height.
A typical floorplan that shows how the components are designed individually and built up
The design architects will have design autonomy in the layouts, but more important, in the external envelope. Bryden Wood has designed a lightweight facade system on a regular 3.2m by 3.1m grid, with thin columns buried in the wall construction to maximise internal space. But the architects will have multiple options for selecting windows, solid panels and balconies within that grid, and will also be able to extend beams beyond the columns to create stepped bays or Zaha Hadid-style faceted curves.
Individual components have been modelled in Solidworks, each with data on its properties attached, such as dimensions, weight, materials and embodied carbon values. The exercise raises the question of how much data to attach: too much and you slow down processing time and waste resources in gathering it in the first place; too little and you compromise the future benefits of linking to Turner & Townsend and Mace’s needs on costs, procurement and logistics, and the client’s needs on long-term maintenance.
But Bryden Wood is in an unusually good position to make those decisions: Johnston is a member of the government’s BIM Task Group and was involved in writing the Demand Matrix – the document that sets out the information to be included in the COBie “drops” or information exchanges. The Solidworks components are then exported into Autodesk Revit to develop the integrated 3D BIM model.
Although Turner & Townsend has to run all the numbers, Johnston is confident that the end result will show savings – in materials, foundations, and the labour costs of a semi-skilled work force – but acknowledges the case hasn’t yet been made.
Transitioning BIM from the design team to cost consultants and project managers will take time, he says. “The Turner & Townsend team are spending time here in our office, I want them to understand how we’ve built up the models so that they can plug our data into the cost plan with confidence. We want them to analyse it and focus attention on where they can add value, not redo what we’ve already done. Further down the line, we can apply cost as one of the attributes of the model, but we’re not at that stage yet.”
Mace, which is currently transitioning from design management into procurement, is also adapting to new methodologies. Bryden Wood has a joint venture with concrete specialist Byrne Group called Integrated Building Products, whose staff are also advising on construction sequencing in St Petersburg, and how the work will be split into packages. This in-house expertise, Johnston says, allows the firm to “programme to minutes and hours rather than saying ‘this takes a week’.”
Incremental gains
PRP Architects is also advancing BIM at a different rate and in a different direction: at Wayland House for Network Housing Association, BIM is more about incremental efficiency gains than re-engineering the process. The project was tendered on the basis of a “Stage D plus planning study”, the design development stage roughly equivalent to Stage 3 in the new RIBA Plan of Work.
But PRP’s Scott Sanderson says having this additional information on materials and specification in 3D rather than 2D gave the bidders a much clearer view of the project – “you can see how the soffit joints flow from outside to inside, and align with the vertical curtain walling sections” – and helped in getting the right outcome.
“When you talk about BIM, clients tend to think ‘oh great, the architect’s got some new pencils’. But actually it’s about buying power, with better information to take to the market the data is an asset for procurement, and then as clients they’ll get better returns on quality, price and risk,” says Sanderson.
Wayland House: the BIM model (above left) shows how the front will look in 3D, compared with the 2D version (above right)
Now that contractor Wates Living Space is on board, the full team has jointly produced a BIM plan. “We all have a feel for BIM, but what exactly do we do on this project? There are opportunity areas in the development and communication of the construction design, and adding quantities to create a 4D model. We’re picking off things to try out, they’re not fixed project deliverables, but we’re trying them, so we can do them [contractually] next time,” Sanderson explains.
One upfront cost-saving for the client is not having to commission marketing visualisations. But apart from this, Sanderson, like Johnston, acknowledges that BIM cost savings might not materialise immediately. “We’re confident the efficiencies exist, we just know it’s a better process. But reducing time and cost mean getting to a point where everything is harmonised and working well, so the efficiency gains are coming in, but it’s difficult to plonk them on the table and say ‘look, we’ve saved 20%’.”
Despite their progress, both design firms acknowledge that BIM is gaining traction more slowly in housing than elsewhere. In social housing, the assumption is that HCA-funded schemes will be required to deliver Level 2 BIM from 2016 along with the rest of the public sector.
But while the HCA announced it would run a BIM pilot around a year ago, little has been heard from it on the subject since. “It would be lovely to get a clear statement on BIM from the HCA,” Sanderson notes.
And as for the UK private house builders, Johnston says BIM is falling on stoney ground. “UK house builders argue that they already have an efficient [delivery] model, and they can’t sell the houses for less [because prices are set by land values and the local market]. So why overturn their business to start again even if it does achieve better results?”
But it seems inevitable that BIM will take hold in housing, whether that involves piggy-backing on mixed-use schemes, using overseas projects like St Petersburg as a testing ground for ideas that are re-imported here, or simply as a result of the 2016 momentum washing over it from other sectors. And when it does, it’s the early adopters who invested upfront that will reap the benefits – while the rest play catch-up.
