Andy Higson, Business Director for Intrastack, discusses how offsite manufacture can help boost the affordable Housing market and help supplement traditional construction to bridge the gap between supply and demand.

Offsite construction has been proven to be an effective solution to housebuilding, offering speed, certainty and lower on-site costs. And as demand for low carbon and sustainable construction continues to pick up pace, they often produce less waste and use less energy. Witnessing high-profile manufacturers of offsite builds struggle to operate a profitable business creates a misguided hesitation over its effectiveness as a viable alternative to traditional methods of construction, which I absolutely believe it is. But what role does Volumetric modular construction play in the housebuilding sector, what challenges does it face, and how do they impact its future in residential housing?

Speed vs cost

There is a balance that needs to be identified between the speed and the cost of the solution, and it’s vital that the decision makers understand what solutions are available and how they best suit the needs of the project they’re working on.

Volumetric modular systems may be fast to produce, but it has added costs associated with it. Some, such as Housing Associations, may be happy to swallow this cost in exchange for providing a large quantity of affordable housing quickly. However, others, such as national house builders, may build a large volume of housing, but they’re not necessarily looking to construct them as quickly, so the added costs are unnecessary.

The reason for the extra cost of volumetric housing is that it’s essentially a fully finished volumetric box. Elements such as the carpets, the kitchen and the bathroom are all fitted in the manufacturing stage before the final modular structure is shipped to site. But to do this, they need to be engineered in such a way that they can be safely lifted and transported without incurring any damage. This means they are inherently over engineered for the final use, and the additional material used to create that temporary structural stability will result in added cost.

If you compare this to other methods of construction, such as traditional bricks and mortar or a panelised system where more work is done on[1]site, it only needs to have the strength to withstand the final building design. This is why volumetric providers are often constrained by very tight, if any, internal margins and are increasingly under pressure to remain competitive, especially for customers that value cost over speed.

Design limitations and placemaking

From a volumetric perspective, there are limitations in tailoring buildings to meet the specific needs of end users. Typically, volumetric modular houses, regardless of whether they have two or five bedrooms, tend to have long and narrow floor plans. This constraint arises from the need to fit the modules onto vehicles for transportation and lifting into their final positions using cranes.

Volumetric providers also face challenges when it comes to attaching roofs to their factory-built structures. Considerations, such as tunnel clearance height along motorways, often require shallower roofs with minimal pitch, which is a common characteristic of volumetric houses. These factors can influence the aesthetics and architectural variety of volumetric constructions. Consequently, if a more intricate design is desired, modular boxes may not offer the same flexibility as a panelised system.

And when it comes to low-rise housing, whether for national housebuilders or housing associations, the focus is on placemaking. It’s not just about maximising the number of units on a site – it’s about creating a residential environment that feels complete and caters to the needs of the residents. Incorporating diverse designs and orientations can greatly enhance the street scene, resulting in visually captivating neighbourhoods.

Standardisation

One of the advantages of modular housing is the ability to standardise the design, which is particularly beneficial for organisations like housing associations or other large-scale affordable housing projects. However, achieving standardisation becomes challenging when it comes to the finished house due to the vast number of variations in elements such as kitchen types, brick finishes, roof finishes, and windows. The potential combinations of these elements can reach thousands, requiring the factory to maintain stock levels of numerous products to provide flexibility. Adequate stock levels are essential to prevent delays caused by running out of fixings, as a halt in the production process can occur until the items are replenished.

The commercial package

Some of the longer standing volumetric providers did some early stage exploration of the low-rise housing market, but quickly backed away once manufacturing costs were set against unit sale rates. As a result, they have continued to focus on more profitable commercial markets, leaving the newer volumetric entrants to learn the larger, more expensive lessons.

When evaluating offsite construction, it is crucial to consider the total commercial package. If the goal is to accelerate construction speed, improve building performance, and ensure programme and cost certainty, then offsite methods are indeed the right approach. However, it is essential to fully comprehend the advantages and disadvantages of different offsite delivery methods and work with contractors who can guide clients through the decision-making process. This prevents uninformed or incomplete decisions regarding the most suitable approach. The commitment and support for offsite manufacturing in the affordable housing market is evident in the initiatives led by Homes England and the industry’s focus. And while progress is being made, there is still a long way to go if we are to offer affordable homes to those that need it.

Looking ahead, a combination of construction methods is envisioned. Traditional construction will still play a role, whether through superstructures like reinforced concrete frames with light gauge steel infill or the continued use of timber for its natural and aesthetic appeal. However, there may be a shift toward elemental masonry solutions, employing large elemental sections instead of traditional breeze blocks. Light gauge steel frames are expected to gain traction due to their ability to address challenges such as fire risk and production speed while maintaining flexibility and commercial viability. Panelised construction is particularly well-suited for low-rise housing as it enables the pre-manufacturing and storage of houses tailored to various customer requirements and house types. This approach ensures that houses are readily available and can be promptly sent to the site when needed.

There is ample market demand for various construction methods, but the commercial model will ultimately determine their viability, especially in the affordable housing sector where affordability is paramount. If the cost of construction becomes too high, someone within the supply chain, whether the volumetric provider, developer, or client, will bear the burden. It is crucial for stakeholders to explore the full range of options beyond volumetric construction and engage in meaningful discussions with the supply chain to understand what can be accomplished. Collaboration and expertise are key factors in ensuring successful outcomes.

For more information visit: www.intrastack.co.uk

Images:

02. Andy Higson, Business Director, Intrastack

01., 03. Volumetric and panelised steel frame offer clients many options for affordable housing

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