Volumetric modular and house-building – why hasn’t it worked?

Homes in the UK are built differently from anywhere else in the world. We love a bit of brickwork, we delight in the difficulties of pouring concrete in the rain and snow, and we are a nation with a proud army of high-vis-wearing site operatives, who work hard in all weathers, and delight in getting their rigger boots as muddy as humanly possible. The vast majority of our new homes are built in situ, on-site using traditional methods – many of them wet trades.

Are we behind our friends across the pond and in Europe?

This isn’t the case elsewhere, in Europe, a much larger proportion of new homes are factory built, using what we would call “modern methods of construction” (MMC), and some of them are panelised “flat-pack” homes that are quickly and efficiently assembled on site, but a significant proportion are “volumetric modular” (VM) where largely complete chunks of a building are transported to site whole and ready to go, with a small number of these modules connected up on-site to create a house. In the United States, this method of construction has been popular for decades, with standard module sizes based on mobile homes being used to construct homes as sophisticated and grand as any other. Known as “manufactured homes” these houses make up well over 5% of new build homes in California, and regional manufacturing businesses there thrive.

Volumetric modular homes in New Islington, Manchester (Phil Cooper, 2018

The advantages of volumetric modular

The advantages are obvious. Factory manufacture:

• Removes wet trades from site

• Allows work to be carried out in ideal conditions without the weather playing any role

• Avoid working at height

• Increases construction speed

• Improves product quality

Importantly, it can allow for significant well-being improvements. I visited one factory where bathrooms were installed on elevated platforms so that plumbers didn’t have to bend over to make connections behind sinks and toilets. They employed a small army of experienced late middle-aged plumbers who enjoyed no longer complaining of back pain and sore knees!

However, the two main advantages quoted are speed and quality. Factory manufacture takes on-site uncertainty out of the equation which means the days spent on site are reduced to an absolute minimum. It also enables a much tighter control of workmanship and provides opportunities for standardisation of design and manufacture that can ensure a level of quality that simply could never be achieved on-site.

The drawbacks of VM

So why has VM not taken off? Why have two significant VM housebuilding ventures failed in 2023, with others pulling out of the market or repositioning?

Firstly, there are some inherent drawbacks to VM that can be difficult to overcome….

• Cost is high – factory operations have overheads that don’t exist for on-site construction. A VM housebuilder I visited in 2018 claimed a per-square-foot build cost of around £120, at a time when the traditional housebuilder I worked for was achieving around £80 to £85. These aren’t absolutely water-tight figures, but the magnitude of difference remains startling.

• Logistics are challenging – VM modules are large and difficult to move, they aren’t suitable for transport to every site, and the complexities of “just in time” delivery and site assembly are significant - I’ve heard of VM companies renting land to store completed modules to avoid stopping work at the factory and to facilitate delivery on site when the ground is ready and the crane is available.

• Workload planning is difficult – traditional builders can use flexible labour and sub-contractors to manage supply chain issues and site delays, but factory costs exist constantly, irrespective of whether a site delay means production needs to stop.

• Flexibility is harder – efficiency in a factory requires standardisation and consistency, changes in design are more difficult to manage, and standard module sizes (limited for transport) restrict the flexibility of design.

Homes in Leeds, built using non-volumetric MMC (Phil Cooper, 2021)

The volumetric modular vs the UK land market and planning system

Secondly, the UK land market is complex, and the planning system is … er… unique! Elsewhere in the world, often land use is set centrally, and planning is granted through a system of permits and prior approvals (apologies for this massive simplification of international planning practice). In the UK, planning is complex, protracted and often unpredictable.

Often in my career as a national housebuilder, I would be asked “How long will it take to get planning permission?” and frankly, anyone who can give you an answer to that question hasn’t understood. Planning in the UK is – rightly – localised, what works in one town won’t be appropriate in another, and what is right for one site won’t be right for another site in the same town, or even in the same street.

Context, as we all know, is everything, and the British planning system is alive to this fact – something we should be proud of, it’s part of what has helped us maintain our built heritage over the decades. Reflect on this, though, when thinking about the benefits of volumetric modular – how can such a standardised factory-based approach respond to local context in an appropriately granular way? How can a system of building that relies on repetition and consistency adapt to the genius loci of Harrogate, Bourton-on-the-Water or Bowness?

Land economy and planning

In Britain, land economy is intrinsically linked with planning, and development land value derives from the ability of a developer to gain planning permission. A key factor of this ability is speed, and VM schemes simply can’t be nimble enough to respond to the nature of planning in Britain. Traditionally built architecture is agile – we can vary the size, the scale, the materials, the fenestration, the details and the character of the proposals almost infinitely. VM schemes can’t do that, and that lack of agility is at the very root of why VM developers have been struggling. They rely on land supply, and consistent workload to make the factories efficient, and if they can’t adapt to the planning requirements of each site, they can’t guarantee the land pipeline and the factories sit idle.

So what’s the Answer?

So, what’s the answer? There obviously isn’t one simple answer, but in a future blog, we aim to investigate other modern methods of construction and consider whether there are good ways of combining the benefits of factory manufacture with a context-sensitive architectural approach.