Industry News
March 28, 2023

MMC Categories

by Oliver Green
Example H2


Only a few countries have had to face up to the daunting truth that, one day, most buildings will be constructed in factories. The construction industry has long harboured the pipe dream of entering the manufacturing age, but has found itself held back by cultural resistance, fundraising restrictions and technological limitations.

At long last, this impasse seems to be clearing. Perhaps it's because the UK is so good at causing trouble for itself that we increasingly find ourselves past the point of no return, with fewer options left open to us that meet today's exacting standards. Against the familiar backdrop of construction's crises (Brexit, Grenfell, COVID), the UK's ageing builders - and with them, traditional construction - are silently disappearing into retirement.

Given that we still need to construct buildings, the decline in traditional construction has caused a gap to open up in the market. What's beginning to fill it in is a largely hidden supply chain that deals in new, experimental construction approaches known as 'MMC' or 'Modern Methods of Construction'.

Yet, despite its celebrity, MMC is an umbrella term which encompasses a lot of things. There is no strict, formal definition of what is - or isn't - a modern way of building. As a result, some have complained it's a bit nebulous and desperately want to ask what MMC actually is, what is its relation to offsite construction, or DfMA? Furthermore - who's actually doing it? Where are they based?  

Luckily, these days we have a formal answer for half of these questions. In 2017, Cast Consultancy, led by Mark Farmer of the 'Modernise or Die' report, published the MMC Categories Definition. This framework has been officially adopted by government and widely taken up by industry.

However, if you want to research the sector you'll still find some challenges. For instance, which organisations are in each category and where are their factories? When we built MMC Market, we set out on a mission to try and build some much needed visibility into the UK's MMC ecosystem, laying bare our MMC factories and the projects they supply. In building the market, we teamed up with Cast Consultancy, in order to gain the benefit of their hard-won industry insights. We have data on hundreds of UK MMC suppliers across all 7 categories, and provide instant, free, unlimited access to all visitors.

With our MMC Market data to hand, we can finally begin to shine a light on what the 7 MMC Categories mean across the UK. Let's dive in.  

Category 1: Volumetric

See all Category 1 manufacturers on MMC Market >

Volumetric modular units are undoubtedly the poster child of offsite construction. These operations exist across the country and are largely high-risk high-reward business propositions. The prospect of high speed, automated assembly lines rapidly turning out perfect, repeatable modules, has captured the imagination of many industry observers.

The UK's volumetric market differs in one key way from many others: we show a strong preference towards steel structures over timber stud. With few exceptions, Cat 1 manufacturers tend to focus all of their work on volumetric systems, whereas other manufacturers might happily span multiple other categories. In another key shift, the UK is one of the few countries taking volumetric modular construction to new heights.  

Category 1 manufacturing facilities mostly seem to focus their outputs on the UK's residential and school sectors, and are reasonably evenly spread around the entire country, barring geography and high land prices (such as near London). Decent motorway access is a must-have consideration as well.  

With their complex transport and lifting requirements, they're undoubtedly an iconic way to build, and one that is popular across the UK. However, because of the many considerations underlying choosing a volumetric solution, it needs to be considered as close to the start of a project as possible. It is generally not possible to switch to using a volumetric solution halfway through the design process.

Finally, volumetric modular is the only Category that has its own dedicated trade group: Make UK Modular. Their members include: TopHat, ilke, Vision, Legal & General and others.  

Category 2: Structural Panelised

See all Category 2 manufacturers on MMC Market >

This category is for 2D structural systems that come to site 'flat-packed' in panel format. Once assembled, these form the building's superstructure. This doesn't necessarily mean the building is watertight or has a rainscreen finish yet.  

Building in panelised construction has several benefits over volumetric: panels can be stacked and brought to site in a more efficient format, since the manufacturer isn't transporting empty 'boxes of air'. Furthermore, these panels can be erected on tighter sites that have access and storage limitations than with volumetric. Similarly, the lifting equipment required to lift 2D panels can be less specialised.  

Most of the technologies in this space are some form of "cassette" system, such as wall, floor and roof cassettes. As with volumetric, there is a range of light gauge steel-based systems, as well as timber stud. Category 2 sees more SIPS and CLT-based solutions than what we find in volumetric offerings as well.  

Category 2 solutions are a bit more forgiving than volumetric when it comes to the project design process: many 2D solutions can be swapped into a project's design at a later stage than a Category 1 solution.

Category 3: Non-systemised Structural

See all Category 3 manufacturers on MMC Market >

Elements in Category 3 are all structural elements that may constitute 'part' of a structure, and be brought in without necessarily being part of a cohesive system for the entire building chassis. These could vary from glulam beams, to lift shafts, prefab concrete stairs and steel screw piles.

These are the kind of MMC systems that can easily be swapped into a project to replace a more traditional system, without having a fundamental impact on the project programme or design approach.

Category 4: Additive Manufacturing

See all Category 4 manufacturers on MMC Market >

Without a doubt the rarest category in the UK is 3D printed construction. While there are plentiful companies with active 3D printed projects happening in the USA, alongside a handful in the EU, the UK has hardly seen any action in this sector beyond a handful of ongoing research projects.

Time will tell whether this becomes an established sector with regular demand for this specialist sector, or whether it becomes another footnote in the history of experimental construction methodologies.

Category 5: Components / Assemblies

See all Category 5 manufacturers on MMC Market >

Assemblies is a broad sector, covering many different non-structural elements. A large portion of these can be considered 'pods', which are pre-finished construction products with mature markets within the UK. For instance, hotels, prisons and student accommodation regularly requires highly-repetitive floor plates. Pods are useful in creating complex assemblies for bathrooms and kitchens where space is at a premium, design needs to be highly considered and variation is kept as low as possible.

Another area that benefits from pre-manufacturing is MEP, where installation on-site can be difficult work (especially on soffits) and which benefit from significant prior coordination in order to reduce their space requirements.

Category 6: Product-Led Improvements

See all Category 6 manufacturers on MMC Market >

This category encompasses all products that seek to put a modern spin on a traditional construction technology. For instance, using a brick-slip system over traditional masonry, or a roofing system with integrated PV panels. As with category 5, these systems are all non-structural and can be considered and implemented at a relatively late stage in the design process.

Category 7: Site-Led Improvements.

See all Category 7 manufacturers on MMC Market >

The final MMC category includes all technologies that augment or improve the traditional on-site building process. The only caveat to this is that there must be some physical product element to the system, such as a helmet-mounted camera, a LIDAR scanner or a drone. This is another side of the industry which has seen significant investment in recent years, such as drywalling robotics, automated setting-out machines and photogrammetry technologies partnered with AI.

As always, if you want to learn more about the specific companies and products in each MMC category, head over to MMC Market!