Production-line homes could be one answer to the UKís housing shortage. But, as off-site manufacture (OSM) prepares to join the mainstream, Serena Ralston asks if planning is lagging behind the technology
In Somerset, a new town of 1,500 modular units made from hot-rolled steel chassis has sprung up in just a year for key workers at the Hinkley Point C nuclear plant.
It is a time frame that would be unthinkable in traditional construction. But Debansu Das of Caledonian, the manufacturer, cheerfully compares modular construction to car production – simple and repetitive design with high-quality control.
Down the M5, on the edge of Bristol, a large 1930s housing estate is undergoing a ‘back-garden revolution’ with rather different modular homes. Here, the community in Knowle West is calling the shots, working with We Can Make
and the Knowle West Media Centre to unlock micro-sites in gaps and gardens for about 300 affordable homes.
The prototype house, which local people can try out for free, uses a compressed straw building system. The homes will be made nearby by trained local people in a neighbourhood housing factory.
In West London this September, students moved into 250-bedroom accommodation nine months after building started on site. The scheme’s planner and designer, HTA Design, is also working on what will be the tallest modular building in the world – a 44-storey build-to-rent apartment block in Croydon for developer Greystar. The building is being built by Tide Construction, with Vision Modular Systems providing the modules. Build-to-rent is expected to be a growth area for the OSM sector.
OSM, not prefab
What these projects demonstrate is the scope of what is variously called OSM and MMC (modern methods of construction), but not ‘prefab’ if you want to keep friends in the industry.
“Today’s homes are unrecognisable from those ‘prefabs’ that are embedded in the memory of many,” insists the London Assembly planning committee’s 2017 report on OSM, Designed, Sealed, Delivered.
“They are now ‘precision-manufactured’ homes that can offer an increased level of consistency and quality control and additional benefits in terms of speed of delivery, cost efficiencies and safety on site.”
The report, which advocates OSM as part of the solution to London’s housing crisis, defines it as “an umbrella term for a system of housebuilding that relies on individual components being manufactured in a factory, transported to a site and mostly, or entirely, completed and assembled on location”.
There are three different approaches:
Volumetric or modular build, where manufactured units are assembled and transported to site as fully finished.
Platforms/sub-assemblies, for specific areas within a building.
Kit of parts, manufactured off site and assembled on site like a flat-pack.
According to the Building Research Establishment (BRE), timber frame structures currently dominate the market, with light-gauge steel-frame structures gaining market share. Cross-laminated timber, an engineered timber product with good structural properties and low environmental impact, is emerging as a newer material.
Although there are no official statistics, the UK market for volumetric modular buildings and portable accommodation is estimated to have increased by 6 per cent in 2017, according to Building Products magazine.
However, a report from the House of Lords Science and Technology Committee last summer found that although OSM can help to increase productivity in the construction sector, the take-up is “varied and somewhat limited across the sector because it is working with outdated and unsustainable business models that are not conducive to OSM for construction”.
The 2017 Budget stated that the government would adopt a presumption in favour of OSM by 2019 across suitable capital programmes. It has made a £1 billion investment through the Home Building Fund to develop new approaches to design and construction. Homes England has made various commitments to MMC, including ncorporating MMC outcomes into its contracts.
But Homes England sounds a note of caution.
“The MMC industry is currently immature, with limited production capacity and supply chains. It requires stimulus if it is to evolve further.”
The industry says it needs government to follow through on its commitment, with enough sites opened up to generate the required throughput. The House of Lords committee report echoes this, recommending that the government should publish “key performance indicators against which the success of the ‘presumption in favour’ can be assessed” and, where OSM is not used, to explain why.
A changing landscape
In the private sector, four companies currently dominate: Caledonian, Vision Modular Systems, Elements Europe, and Premier Modular. But the OSM landscape is changing rapidly, with new and very different operators joining.
Swan Housing Association, which opened its own modular housing factory last year, will produce 300-400 modular homes a year. Of these, 560 will be used for its regeneration of the Craylands Estate in Basildon.
Legal & General is expected to deliver its first factory-built homes at the end of 2018 after it opens its own modular factory near Leeds. Then there are the Silicon Valley investors: in the USA, Amazon has invested in Californian home design and prefabrication company Plant Prefab, with plans to integrate its voice-controlled Alexa devices into the homes.
“A lot of people think that construction is ripe for disruption, so OSM is very timely,” says Bergin. “The UK is attractive to US investors in OSM because contracting prices are high here and building is slow and risky.”
BRE says OSM is arguably cost-neutral – with higher factory costs but lower on-site costs. But speed and quality control are big benefits. Time savings are typically between 30 and 50 per cent on a traditional build, according to Debansu Das. Caledonian, for example, makes 2,880 modules, or 1,400 apartments a year.
“Quality control is a real advantage – what is delivered is what is specified,” says Das. “Modular is fully audited with a gated process in the factory at every stage of production.”
Another major advantage is that OSM can use unconventional spaces as purpose-built modules are lowered into place by crane. For example, ZEDpod modular homes are designed for land typically outside the development plan such as on top of city centre car parks.
In October, Bristol City Council committed to investing in six, an example of which was displayed at the recent Bristol Housing Festival. These will be offered to people in housing crisis within six months, subject to planning approval. The council has pledged to release normally undeliverable sites to the festival for testing and delivery of different sorts of housing and communities over five years.
Apartments for London announced in September that it had entered a new partnership with Transport for London (TfL) to create modular homes over car parks and other sites on TfL land. Planning applications for the first three developments, with the potential for about 450 affordable homes, are in the pipeline.
OSM is also said to be more sustainable than traditional build methods, using less energy, with fewer transport trips to site. Factory manufacture also has other attractions related to working environment and availability of skills.
“You wouldn’t build a sports car in a field, so why a house?” says Dr Rehan Khodabuccus, operations director at ZED Pods. “Modular offers far better quality control and we have a greater continuity in our workforce.”
Nevertheless, a challenge for planners and developers is that design decisions need to be made early on and adhered to in the construction process. In contrast, the traditional contracting model allows for last-minute on-site changes.
Despite OSM’s advantages and its scope, there is a planning policy and knowledge gap that the industry figures we spoke to would like to see addressed. It is thought that the draft London Plan contains the only planning policy on the issue.
“Traditionally, planning policy doesn’t support housing on difficult or market failure sites,” continues Khodabuccus. “But if we don’t want to build on greenfield, if we want to tackle difficult sites, we need to go with modular and we need policy support. The industry is also crying out for specialist planning consultants – we are educating the planners.”
Among the suggestions that the industry would like to see to provide it with greater security are sites earmarked for OSM only, or planning policy that mandates a minimum amount of OSM in a development plan.
Construction firm Mace has asserted that applications for MMC projects could be accelerated for projects that can demonstrate faster, better-quality and greener developments than traditional approaches.
Debansu feels that national planning guidance would give more clients and developers the confidence to switch to OSM. Caledonian is helping in this process by running workshops for councils in London.
He adds that owing to the sector’s efforts more planners are favouring OSM as it creates less disruption for the surrounding community because of fewer deliveries, and it has shorter build schedules.
We Can Make is working with the local community and others, including Bristol City Council, to develop collective tools to help make delivering an affordable home on micro-sites easier. One of these is a design code whereby the community will help set the rules for any modular homes on micro-sites – including how many, where they go, suggested materials, and how they relate to the existing housing stock. This could eventually be adopted as supplementary planning guidance.
Planning clearly matters here. Although late to the party, it has the potential to support and shape the delivery of OSM homes as part of solving the national housing shortage.
Case study: Off-site on site at Highbury II
In September 2018 students moved into Highbury II, a 257-bedroom accommodation block forming part of the former Arsenal stadium redevelopment, a mere nine months after building started on the North London site.
Rory Bergin of the scheme’s planner and designer HTA Design, says: “This time frame would have been inconceivable with normal construction. The site is next to the railway line, so you couldn’t get a more challenging setting.
The scheme, for Greystar’s student accommodation brand Chapter, was built by Tide Construction with 308 modules from Vision Modular Systems.
“Everything was delivered as the finished product – rooms came with a bed, desk and lighting. The only thing missing was the student. Off-site manufacture is ideal for student accommodation as well as accommodation for the homeless.”
Serena Ralston is a freelance journalist specialising in planning and the built environment.
This article was first published in The Planner magazine in December 2018 and is reproduced with permission. www.theplanner.co.uk