Offsite construction: advantages in terms of cost and efficiency

The construction industry has been slow to adopt offsite techniques despite the savings in time and money they offer developers when compared to traditional onsite techniques. Offsite methods also typically produce less local disruption and environmental harm. Here, we go over their financial and operational benefits.

The efficiency of offsite construction

Britain is a "laggard country" when it comes to off-site building. Offsite construction techniques are used in less than 5% of British construction, compared to 9% in Germany, 12-15% in Japan, and 20% in Sweden.

Nonetheless, Legal & General owns the world's largest modular construction facility, which is located in Sherburn, Yorkshire. They claim to be able to create 3,000 new homes every year, demonstrating that onsite construction is not a foreign notion in the British construction business.

The benefits of employing offsite construction were outlined in a 2013 paper commissioned by Buildoffsite, a business organisation aimed at catalysing the usage of offsite methods in the British construction industry.

A significant theme of the research is that because offsite construction shifts most of the building process from the construction site to a factory, the procedures and conditions are more similar to those of the manufacturing business than those of the traditional construction industry. This distinction underlies many of the advantages of offsite building over onsite construction.

Offsite construction is less labour intensive

Prefabricating construction components in a factory can be significantly more automated than the typical onsite brick-by-brick process. The fabrication of kitchen and bathroom pods in a factory, in particular, allows the rooms with the most complex mechanical and engineering components to be prefabricated and transported to the site without the need to coordinate workers with various skills, often working for different subcontractors, who are required to construct kitchens and bathrooms onsite.

The potential of computers replacing human labour, snatching our jobs, and leaving us unemployed and penniless is raised by automation. However, in the context of a construction industry facing a severe labour shortage, the scenario appears far less ominous.

According to the Construction Leadership Council's 2016 Farmer Review, four workers depart the construction industry for everyone hired. The shortage of competent labour is expected to worsen because roughly one-third of construction workers are over 50 and will retire within the next 15 years.

Because the sector will need to make do with fewer personnel in the coming years, automation provides a solution to fill the void left by retiring individuals.

The Farmer report highlights many training and recruitment programmes that will help relieve the situation, but the calculations show that the construction industry can only fall short of the government's target for home building by roughly 50% if it continues to operate as it is.

Either the sector needs to hire more people than five times as many or it needs to adopt less labour-intensive strategies like off-site building.

Consider the Japanese lessons described by William Johnson of the Bartlett School of Planning. Japan faced a worse construction skills shortage than Britain, which was exacerbated by an older population with many people retiring and poor recruitment into construction, a very restrictive visa system that prevented recruitment of migrant labour, and a "scrap and rebuild spiral" in which houses are demolished and replaced at a rate that is roughly eight times that of the UK.

The Japanese embrace of offsite construction is key to Japan's annual offsite home production alone, which is around three-quarters of the UK's entire home production.

While the United Kingdom is currently experiencing a housing shortage, Japan is experiencing a housing surplus.

Offsite construction cuts the cost of installing building services

Many earlier tower blocks provided amenities such as hot water and ventilation via central plants linked to each flat via a network of pipes and ducts that required vast rooms or basements to house the plants. Pipes and ducts occupy communal spaces such as corridors, all of which must be accessible when it's time to find a leak or ensure that the lagging is still effectively insulating them.

Such centralised systems may be replaced by more localised systems in modern buildings. For example, rather than relying on centralised plants, ventilation is managed by demand-controlled ventilation systems in each apartment, and superior insulation in modern buildings allows central heating systems to be replaced with electric convection and infrared heaters in each room.

Such localised systems require the installation of personnel with specialised abilities, and each of them requires a certain set of supplies, which are logistically much easier and thus cheaper to manage in a factory than onsite.

When building services are included in volumetric units, they can be constructed with a small number of electrical and plumbing connections that can be simply plugged in when the building is assembled.?

Less Time Onsite

Because much of the construction is moved from the site to the factory, a development spends less time on the construction site. The amount of time saved depends on the nature of the construction project and how much is done offsite, but according to the Buildoffsite report, it can range from 25% for large buildings like office blocks and supermarkets to 60% for simpler projects like schools.

Aside from saving money on hiring generators and cranes, anyone who has ever had to perform an environmental impact assessment will appreciate the opportunity to minimise local disruption. Some planning authorities hold the notion that no construction site should ever be noisy or dusty. While offsite construction will not satisfy a planning authority, it can reduce the length of onsite time that they will need to authorise.

Offsite construction offers better safety and working conditions

Moving construction work from a site to a factory effectively implies working in manufacturing-like settings. Working indoors must be preferable to working on a construction site during the next 'beast from the east," but the Buildoffsite research points out that there is an even deeper reason why offsite construction is preferable: workers are less likely to die. Despite significant improvements in safety over the last three decades, the Health and Safety Executive finds that the construction industry still has a fatal injury rate more than three times that of the manufacturing industry.

The construction sector's fatal injury rate of 1.64 per 100,000 employees per year remains low: to have a 50/50 probability of a fatal injury, a worker would have to work in the business for more than 30,000 years if modern safety standards are maintained until 32019.

However, this appears to be worse than the 95,000 years that people would have to spend in the industrial industry to be at risk.

More concerning is the impact that working in construction can have on a worker's health, particularly the various ailments classified as musculoskeletal disorders by the Health and Safety Executive: the various things that can go wrong with a worker's back or limbs after years of heavy lifting even if he's never had an accident.

With a rate of 2,310 per 100,000 workers per year, a worker only needs to be in the sector for 22 years to have a 50/50 risk of acquiring a disease. That's one of the highest musculoskeletal disorder rates of any industry, and more importantly, for offsite construction, it's roughly twice the rate in the manufacturing industry.

Offsite construction would mean that construction workers would spend more time shielded from the vagaries of British weather, with their feet on firm ground and much of the heavy lifting performed by machinery safely attached to the floor.

In addition to being safer, the improved working conditions may help to change the reputation of construction as an unpleasant industry to work in, as stated in the Farmer report, and so enhance recruitment. Offsite construction reduces traffic.

Any environmental impact study would consider how many cars will transport personnel and materials to the construction site. The neighbours are already tired of the school-run traffic bottleneck, and a convoy of trucks only adds to it. They also don't want a parade of diesels belching nitrates down their leafy street.

Offsite construction cannot eliminate the need for cars and trucks entirely, but by shortening the time spent on site, locals will not have to put up with it for as long.

Perhaps more importantly, offsite construction tends to replace a big number of small vehicles with a small number of huge vehicles. Unless the site is especially difficult to access, a large vehicle does not contribute significantly more to a traffic delay than a small one, and it produces far less noise and air pollution per tonne of load.

A single lorry delivering all of the building's wall panels will bother the locals far less than a swarm of vans bringing cement powder.

Offsite construction offers greater manufacturing precision

Since the implementation of Part L of the building regulations in 2010, new structures have been obliged to meet stringent insulation criteria. To achieve such requirements, the building design is subjected to the standard assessment procedure (SAP) to guarantee that it does not leak excessive heat, either through conduction through the building fabric or air moving through the building. Once completed, the building is reassessed, including a physical pressure test to determine that it is as airtight as it was supposed to be.

The assessment's estimate of the building's energy performance is only as good as the building's adherence to the design, and it's much easier to match design parameters accurately in a factory than on a construction site. That means the design doesn't have to account for the margin for error required for onsite building, and once completed, it can be handed over to the owner with total confidence that it will use as little energy to keep it warm as the design claims.

In addition to energy efficiency concerns, the Buildoffsite research predicts that the expense of correcting building defects often adds roughly 2% to construction costs, which might mean the difference between winning and losing a bid. The analogous statistic for the manufacturing industry is close to zero, demonstrating that faults in the factory are simply much less common than on the construction site. Moving construction offshore reduces the expense of repairing them. Offsite construction generates less waste

According to the most recent official statistics, the construction industry accounts for more than half of all waste produced in the UK, and while much of it is recycled, a significant percentage still ends up in landfills. Perhaps more importantly for the developer, the Buildoffsite research predicts that construction waste accounts for 3-5% of the cost of a building project, which is far more than the 1-3% waste cost in manufacturing.

The difference is due in part to the fact that industrial processes are far more predictable than those on a construction site, allowing supplies to be ordered according to more precisely predicted requirements, and in part to the fact that handling waste is easier and less expensive in the factory setting. Offsite manufacturing generates less greenhouse gas

Aside from the solid waste that is disposed of in landfills, building machinery cannot avoid emitting numerous toxins into the environment. However, if air pollution cannot be prevented, it can be reduced. We've already spoken about how lowering work traffic reduces toxic nitrates, which restricts local air pollution, but greenhouse gases like carbon dioxide are a larger global issue that is already causing major climate change worldwide.

John Barrett and Thomas Wiedmann calculated the greenhouse gas emissions of a typical newly built house in the United Kingdom, using either off-site or onsite construction processes. They discovered that switching from onsite to offsite construction would reduce greenhouse gas emissions by 17% to 30%.

Barrett and Wiedmann's model took into account both the building and the energy usage of the house while people were living in it. They discovered that the materials used in offsite manufacturing produced around half as many greenhouse gas emissions as onsite materials while also providing a far more energy-efficient fabric for the house.