Offsite manufacturing & modular construction

What is offsite manufacturing?

Offsite manufacturing (OSM) and modular construction are methods of building where components are made remotely, then delivered and assembled on site. Components may include wall, roof or floor panels or even complete rooms.

Whilst historically these construction methods have been used widely on larger scale projects, OSM processes and technologies have now developed and are becoming more cost-effective, therefore being suitable for use on smaller developments and even single unit residential schemes.

View Architecture for London’s portfolio of recent projects.

Can OSM solve the Housing Crisis?

We need to be able to use innovative technologies to address London’s most pressing problems. One of these problems is the shortage of high-quality, environmentally friendly homes located in the areas that people actually want to live.

In both the private and public sector shortages prevail, for example since 2015, the GLA has only been able to deliver 60,000 of the targeted 116,000 homes by 2022. Housing provision is a multi-factored issue, with funding playing just as much of a part as land availability and construction methodology.

A proposal for an OSM CLT timber frame cafe and housing in Southwark

We believe that modular housing is one of the ways to help address the shortfall of both affordable and market-rate housing. As outlined by the Farmer Review in 2016, modular construction can dramatically reduce the embodied energy of the finished build, by using sustainable materials, high levels of airtightness, incorporating water collection systems, and reducing material wastage.

Low-standard prefab production in the 1950’s created units that are generally ‘unmortgageable’, fueling further negative stigma about modular construction. Housebuilders, financial institutions, architects, and homeowners need to reconsider their position on modular construction. Through the use of robust materials, the homes created can be durable and high performance.

Modular housing case studies

UrbanSplash’s Manchester development demonstrated all of the benefits of the modular approach in a real-world scenario. The cost savings and solid environmental performance were passed on to the end-users. Homeowners were able to purchase large footprint homes which were cheaper per square metre than city-centre flats, cheaper to maintain, cheaper to heat, but with the added benefit of high ceilings and large windows.

Building on the successes of developers like UrbanSplash in Manchester, there is now an appetite within the government to speed up adoption, skills and production levels within the industry. In 2019, the government began releasing funding to increase production output from the UK’s modular factories.

Advantages of offsite manufacturing

Offsite manufacturing can be particularly effective on constrained London sites, where there are often significant limitations on working area and storage. The off-site construction also allows for simultaneous progression within the building program, the OSM homes are built while foundations are being laid on-site, reducing the time on-site by roughly 50% in comparison to a traditional build.

The time saving and reduction in the number of builders required has a two-fold benefit; firstly, creating cost savings which can free up part of the budget for delivering more homes and secondly, less time on site, means fewer vehicles arriving at the site and a lowered carbon footprint. Disruption to neighbours is also minimised, this is a key benefit on dense urban sites in London.

A proposal for off-site manufactured CLT timber frame housing in Southwark

A fast construction process also typically leads to reduced preliminaries costs, for example in scaffolding hire. Whilst the programme is shorter, it should also be more reliable, as factory-based work is not weather dependent.

OSM can also be closely controlled, meaning the work may be completed to a higher standard of quality and with better safety standards. This also gives the potential for more energy-efficient buildings, with improved airtightness due to precision fitted seals and membranes. There is a reduction in waste during construction and there are also building life-cycle considerations.

Disadvantages

Depending on the materials and systems chosen, OSM may impose design limitations. For example, CLT has only been used for buildings up to 9 storeys in the UK. It is also crucial to reach an early design freeze as flexibility for changes on-site is limited.

Currently, there is a lack of UK suppliers for larger prefabricated components when compared with the rest of Europe. This can lead to comparatively higher costs for OSM projects in the UK. There is also a lack of public awareness of these modern methods of construction which may lead to a reluctance to use them.

Summary

An analysis of cost, quality and time will determine the direction of any building project. The potential for shorter construction programmes and improved quality of product are key selling points for OSM. Whilst we are already seeing the rise of modular construction in London, we are likely to see a more dramatic uptake in the future, as cost-effectiveness also becomes a key selling point, arising from supply chain improvements and industry familiarity with these technologies.

At Architecture for London, we believe that modular housing developments will be a key part of boosting production and creating good quality homes for every Londoner. Our approach to modular homes is no different to our other housing developments. Despite making use of unit repetition, we believe developments can still engage successfully with the urban realm at multiple scales.

With some careful thought, architects can create modular developments with character that meet the needs of residents and of the broader community.

Current AFL projects can be viewed on our housing page, or contact us to discuss a project that may benefit from offsite manufacturing.

Image credits

Architect: Jørn Utzon, prefabricated Bagsvaerd Church, Copenhagen.

Photographer: SEIER+SEIER.