Defining prefabrication
Most simply, prefabrication - also known as off site manufacturing or modular construction - refers to construction projects which are completed at a different location to where they are installed. From cost efficient and rapid project turnover to valuable opportunities to level-up both digitalisation and sustainability, in this article we delve into how prefabrication is much more than just an easy alternative to traditional construction.
Timber and prefabrication: a match made in off site heaven.
When it comes to prefabrication, the materials involved are typically either precast concrete, steel, or timber. Compared with other construction materials, our beloved timber arguably delivers the most crucial advantages offered by prefabrication. What we all love about timber is its light and reliable nature. Both qualities make it ideal for off site manufacturing: the logistics of transporting prefabricated components to their intended destination are made simpler; timber materials such as spandrel panels, floor cassettes, and ready fitted windows for example, are commonly manufactured off site and offer seamless delivery and on-site securing without the time-intensive processes of conventional construction.
Moreover, off site provides the ideal conditions for ensuring uniformity of build. With the prefabrication process itself taking place in controlled factory environments, both precision and quality control are easily kept to a high standard. Thanks to standardisation and in-factory quality checks, the off site manufacturing defect rate can be at the very least halved, while among best-in-class producers, the defect-free rate on new buildings reaches over 95 percent.
Environmental risks are also much lower, as prefabrication reduces on-site casualties and hazards by 20 percent. While loose joists and forklifts used in conventional construction necessitate greater manual labour while increasing exposure to health and safety risks, prefabrication minimises hazards as well as labour demands. Amidst continued skills shortages, the latter quality offered by prefabrication has become increasingly attractive.
In a controlled factory environment, a smaller number of skilled workers can also maintain a higher attention to detail and focus on the precision required to meet the required standards.
Speedy turnover
When operating under a tight schedule, prefabrication offers a wealth of advantages to traditional construction. Arguably the most attractive aspect of off site timber construction is that it offers a highly efficient turnover, taking minimal time from assembly to completion. Off site construction can deliver projects 20 to 50 percent faster than traditional methods, in turn providing cost savings of up to 20 percent. Naturally enough, onsite preparation is minimal given the most crucial elements of construction take place off site and earlier in the process. Pressing schedules amidst increased demands for housing across Europe means that now is a great time to make the most of off site manufacturing processes and prefabrication.
Off site construction has long proven especially popular in the Netherlands, with 93 percent of Dutch contractors having applied prefab in projects at some point. The Dutch style of home construction is particularly suited to prefabrication, easily applied to the standardised row of houses commonly found in the country. Given the country’s target to reach one million new homes by 2035, off site manufacturing’s speedy construction timeline makes it a foolproof option to gear up its housing supply while simultaneously contributing to the country’s green ambitions of curbing nitrogen emissions created by conventional construction activity.
In the UK, the Government’s introduction of a ‘presumption in favour of off site’ for projects was announced in 2017, bolstering its commitment to Modern Methods of Construction, and specifically citing certain industries most suited to off site construction. Such projects pertain to those related to the departments of education, defence, justice, transport, and health and social care. England alone needs up to 345,000 new homes annually, while the total national housing stock is currently failing to meet the level of demand. Accelerating the construction timeline might be an obvious advantage delivered by off site manufacturing, but for projects situated in urban environments, prefabrication offers further incentives, delivering reduced disruption to the surrounding communities.
Sustainability
As pressures build to meet demand, the industry is increasingly aware of the need to do so in a sustainable manner. Timber offers much less waste than concrete, for example, while cast-in situ concrete has also been found to have greater carbon emissions when compared to precast concrete or indeed prefabricated timber. According to the British government, its target to reduce carbon emissions to zero by 2050 means it must increase the use of modern methods of construction such as off site in order to create infrastructure and built assets that are higher quality, more sustainable and a better fit for future users. As we know, one of the principal benefits of timber is its carbon sequestration, meaning that for every cubic metre of timber used in construction, an estimated 0.9 tonnes of CO2e is sequestered and stored for the lifetime of the building.
When it comes to prefabrication, what timber products are in use?
Some timber products lend themselves especially well to prefabrication. In recent times, mass timber innovation has carved itself a spot as a serious contender for high-quality off site manufacturing. Cross-laminated timber (CLT) - often dubbed ‘super plywood’ - is a highly versatile material often used to build floors, walls, and roofs, while other engineered wood products popular in off site construction include nail-laminated timber (NLT); dowel-laminated timber (DLT); laminated strand lumber (LSL); laminated veneer lumber (LVL); and parallel strand lumber (PSL). Mass timber is engineered for high strength ratings which match concrete and steel, but comes in at a significantly lower weight.
Off site light timber frame construction is also an attractive choice for certain projects, typically composed of panels of up to 10 metres in length and often utilised for light-frame walls, floors, and roof trusses. Lighter wood panels can be advantageous as they mean that foundations do not need to be as large, while smaller cranes can be used to lift panels higher. Whether opting for mass timber or light frame, either material used in prefabrication brings a set of advantages which can combat challenges both on macro industry and micro project levels.
Digitalisation
With the digitalisation of the industry picking up pace, there is major potential for off site manufacturing to deliver new levels of productivity and efficiency thanks to harnessed digital technology. Recent research has found that due to its similarity to industrialised products, off site construction can be identified as a focus for the transformation of Construction 4.0. The mature industrial frameworks and techniques that have come with Industry 4.0 therefore bear significant applicability to prefabrication, offering the distinct opportunity to combat the construction industry’s prevailing reputation for lagging behind in the use of modern industrial digital tools.
As the construction sector’s arrival to Industry 4.0 advances, prefabrication offers a set of solutions that converge at a sweet spot of digital advancement, sustainability, and cost-efficiency. With advanced technologies such as Building Information Modeling (BIM), robotics, and automation, further enhancing the precision, quality, and cost-efficiency of off site manufacturing, its positioning as a crucial aspect of construction in the 21st century is indisputable.
At VonWood, we lie at the crossroads where production meets trade. We’re proud of being at the cutting edge of the industry, while it’s just as important to us that we maintain a deep respect for how our industry has evolved to get us here. With this in mind, we are always excited to share innovations such as those in prefabrication with you, knowing that together we safeguard the rich legacy of our trade by embracing its evolution into the future. To find the right timber for your needs, you can get in touch with us at info@vonwood.com.
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