What is MMC?
In 2020, then housing secretary Robert Jenrick said that he, chancellor Rishi Sunak and the chief secretary to the treasury Stephen Barclay were “hugely supportive” of using modern methods of construction to build homes.
The government has made it a condition of their £11.5bn affordable homes programme that at least 25% of those homes should be manufactured through modern methods.
The Government’s new Modern Methods of Construction (MMC) Taskforce, backed by £10m of seed funding, aims to accelerate the delivery of offsite homes across the UK, working closely with housing associations and local authorities to achieve this.
In 2019, a MMC definition framework was developed by a government and industry working group on MMC. It covers seven MMC Categories.
The framework was developed to regularise the term ‘MMC’ by defining the broad spectrum of innovative construction techniques being applied in the residential market.
Category 1 – Pre-Manufacturing – 3D primary structural systems
Category 1 volumetric, three dimensional ‘boxes’ are manufactured in factories and delivered to site. Typical systems include timber, steel or cross laminated timber (CLT). This category has the highest level of pre-manufacture.
The Category 1 segment of the offsite market is more mature than some other categories. There are a number of large-scale Category 1 factories in the UK that have already been delivering residential MMC homes for some years.
Category 2 – Pre-Manufacturing – 2D primary structural systems
These are two dimensional panelised systems, manufactured in factories and assembled onsite to form a structure.
There are many differences within 2D categories: standard timber, cross laminated timber (CLT), steel, structural insulated panels and hybrid systems.
Category 2 systems have the ability to be manufactured to a client’s own individual designs and house types. They can provide bespoke solutions to sites that might already have planning, without housing organisations having to go back to the drawing board. 2D panelised systems are also easier to transport so they are more suitable for sites with access issues.
The Category 2 segment of the offsite market is evolving rapidly with new products and manufacturers emerging all the time.
Category 3 – Pre-Manufacturing – Non systemised structural components
This includes the use of pre-manufactured components to form part of the structure of a building, mostly made from timber or concrete.
Typical types of Category 3 MMC components are driven or screw piles, pre-fabricated pile caps or ring beams, columns, walls and/or beams, floors, integrated columns and walls and beams, staircases and roofs.
Category 4 – Pre-Manufacturing – Additive Manufacturing
This type of MMC solution relates to the 3D printing of parts of buildings and it can be done remotely or onsite.
Although this form of MMC is not available for widespread use in construction projects currently, it is expected to be in the future.
Category 5 – Pre-Manufacturing – Non-structural assemblies and sub-assemblies
Category 5 covers pre-assembled components that do not form the structure of a home and can be used in isolation in an otherwise traditionally constructed project.
There are two main types of MMC Category 5: 3D components such as pods and 2D components such as façades, floors and walls.
Category 6 – Traditional building product led site labour reduction/productivity improvements
This category comprises traditional building materials that have evolved so that they are quicker, easier and safer to install. They are either large format versions of traditional materials, or materials that have been developed to be easier to install with less reliance on onsite labour.
Category 6 solution types include internal walls, external walls, roofing finishes, materials that have been specifically cut to size, e.g. pre-sized plasterboard and also materials that have been adjusted to be easier to install, e.g. brick slips.
Category 7 – Site process led labour reduction/productivity improvements
This includes the use of systems and processes onsite to drive productivity by removing unnecessary work stages, enabling better and faster installation and improving health and safety.
Examples include measures to encapsulate a site to secure weather-proof conditions, standardised temporary work (e.g. a modular scaffold), use of BIM connected to onsite workflows, visual aids such as AR or VR, physical aids such as exoskeletons and productivity tools such as GPS.
The short answer is no as it depends on a number of factors. There has been a huge reduction in capital costs over the past decade and these will continue to come down, as our pipeline grows bigger and longer.
We know the real cost reduction is in improved quality, but there is little data backed evidence of this. Building Better will continue to collect and investigate means to link the capital cost of new development to ongoing costs of housing management, maintenance and service charges.
In principle, no. In fact, with the use of Building Information Modelling (BIM) and other digital technologies which are inherent in the manufacturing process, repairs and renovations could become proactive, more efficient and less intrusive.
In practice, our asset management teams need to be involved in the development process from the beginning to ensure repairs are not attempted in the same way as would be the case with a traditional brick / cement structure.
The biggest challenge is around insurance and the risks associated with
This is a myth, which has been busted since the market moved on from pre-fab buildings made in the post WWII era. It is possible to standardise performance, processes and even layouts but still retain differences in how homes look on the outside.
In fact, the more we standardise across defined criteria, the greater the ability to customise additional elements.
A closely controlled factory environment allows complete control and assurance over quality management. Some manufacturers have modelled how these practices lower future costs, however, there is simply not the volume of homes to prove this point.
Given the lack of repeatable and scalable evidence, Homes England has launched an in depth study in addition to independent research projects such as Homegroup’s Innovation Village in Gateshead.
Building Better members used the procurement process to compare manufacturers on both capital costs and evidence of improved quality via metrics such as Energy Performance Certificate (EPC) and Standard Assessment Procedure (SAP) ratings and air tightness.
Delivering operational net zero carbon homes at scale is a priority for many housing providers and a key driver behind the use of MMC.
The carbon footprint of traditional construction is substantial and MMC helps housing organisations to build greener homes in greener ways.
Embodied carbon emissions are reduced through quick, precise manufacturing processes, wider use of recycled materials, minimal waste, reduced lorry deliveries and less travel for workers all help to reduce the carbon emissions of MMC homes.
Noise and vehicle pollution are also significantly reduced – offsite homes can be completed up to 30% faster than traditional – and that also means there’s less disruption for residents.
Most MMC homes are ‘fabric first’ so they use high performance, long-lasting materials for maximum insulation and ventilation and they require less energy to run. This cuts operational carbon emissions, and it also lowers the cost and carbon footprint of future asset management. Technology gathers data about the condition of materials and products from the moment MMC homes are assembled and this, too, helps to reduce downstream maintenance.
Crucially, with energy costs surging, the thermal efficiency of offsite homes has never been more important. Electricity bills in MMC houses and apartments are significantly lower and one manufacturer recently launched ‘Zero Bills’, the UK’s first home to guarantee residents zero energy bills.