Onsite vs. offsite construction: which is right for my M&E projects?

If you are planning on starting an M&E project, you might be wondering whether to adopt offsite construction as it is becoming more popular among UK contractors, or to stick to the traditional ways of onsite construction.

Although here at MIDFIX we have a designated fabrication innovation centre dedicated to offsite manufacturing, we appreciate that it is not the best option for everybody and the ultimate goal of this article is to help you figure our what’s right for you – so it is written objectively.

Each method comes with its advantages and disadvantages, and there are a number of factors to consider that will determine the route you should take, such as: cost savings, time, health & safety, labour, customisation, weather conditions, sustainability and carbon footprint – let’s talk about how they compare with respect to these categories.

Health & Safety

With traditional/onsite construction, labourers are continuously exposed to dangerous working conditions, making them prone to falls, structural collapses and other injuries, as well as weather-related injuries. On the other hand, safety concerns and risks are reduced with offsite construction as most of the labour takes place indoors in a controlled factory environment, and it would be done by a smaller number of staff, making it the clear safer option. In terms of the safety of the building/structure itself, offsite manufacturing requires careful preparation and testing to ensure as much safety and as little risk as possible. The government is planning to introduce a requirement as part of a stricter regulatory regime for all buildings and construction projects called the ’golden thread’ – which is the information about a building that allows someone to understand a building and keep it safe, and the information management to ensure the information is accurate, easily understandable and accessible (GOV.uk, 2021). While this will help onsite projects become better tested and safer in the future, it won’t be an extra step for offsite since this level of compliance already takes place.

Winner: Offsite

Customisation

When designing for an offsite construction project, extreme detail and planning is required – however, afterwards, once the project starts, there can be no changes made to the design or plan. There are also certain limitations when it comes to prefabrications’ sizes due to transport restrictions, maximum road widths, weight limits etc. This means there is less room for error and customisation is limited. In contrast, onsite construction allows for much more flexibility because changes to the design/plan can be made whenever, and in accordance with any issues or delays that may arise at the site. Of course, it is recommended to keep changes to a minimum as this can result in project delay; nevertheless, it is good to have the option to do so under necessary conditions. Aside from this, it is also easier to undergo renovation to an already built structure when it is onsite.

Winner: Onsite

Quality

If time and early engagement is not a major concern, but you want to ensure the products are made to the highest of standards, then offsite manufacturing is likely the best option for you due to the due diligence and full design compliance that takes place before starting a project, as well as the quality management procedures that occur throughout.

Winner: Offsite

Time

As mentioned, offsite construction calls for extremely detailed planning. While this can be seen as a positive, it is also time consuming and requires meticulous detail and effort. Also, for it to be beneficial for anyone, engagement should begin from early on; whereas with onsite manufacturing, a project can start with shorter notice. However, though the initial planning might make it seem more time consuming at face value, the quality control ensures everything is made to be fit and done correctly the first time, therefore reducing the risk of errors and subsequent project delays. Besides, when the Golden thread of information is introduced, it will become the duty of anyone responsible for a building, regardless of onsite or offsite construction, to maintain the information about it that ensures its safety – so this ‘time-consuming planning’ aspect will no longer just be true for offsite projects. Though it could also be argued that such precision is not as imperative with onsite, since changes can be made accordingly. Building can start at the same time as site preparation with both taking place simultaneously, instead of having to wait until after the site has been prepared, which saves valuable time. As well as this, because offsite solutions need to be planned ahead, there will be a reduced number of deliveries – instead of requesting deliveries based on what is needed tomorrow, they will be grouped together, making the process more time-efficient. Additionally, weather conditions are a key element that can cause delays in onsite manufacturing, and there are less external disruptions with offsite manufacturing.

Winner: Offsite

Location

If you are looking to start an M&E project in an urban, tightly congested area, then onsite construction is the best choice for you. Not every location is suitable for an offsite project. This is due to the transport restrictions, maximum road widths, and weight limits mentioned earlier. Despite onsite construction being more prone to obstructions, it prevents the hassle of having to move larger modules into small spaces. For this reason, onsite is likely the more suitable option for a higher number of potential locations than offsite manufacturing.

Winner: Onsite

Labour

Manual labour will always be needed - especially in the construction industry - but there are certain factors that can reduce or increase the amount of manual labour required. For example, because of offsite construction’s ability to allow designers to create and manufacture structures intricately and thoroughly, the need for more workers that are skilled in different areas, such as specialist welders, is mitigated, making the process less labour intensive (Miles, 2019). Prefabrication in a factory also involves more automation, which, in the construction industry, is a good thing due to a severe labour shortage. Not to mention, the working conditions are much easier in a factory as opposed to the unpredictable conditions outside, and less workers means less safety risks. To add, the reduced number of deliveries also accounts for less labour.

Winner: Offsite

Sustainability

Along with reductions in labour, offsite solutions are optimised to ensure that there is efficient use of materials, which also leads to a reduction in waste and energy usage and is overall much better for the environment. On average, 67% less energy is used to produce a modular building, the need for assembly stations is minimised, and up to 50% less time is spent onsite when compared with traditional methods, resulting in up to 90% fewer vehicle movements around the project which in turn, reduces CO2 emissions (Modular vs. Traditional Construction, 2016). Moreover, solutions are moved from one source instead of multiple, once again reducing CO2 emissions. The need for hot works would also be diminished due to the factory-controlled environment. As a result, offsite construction would reduce carbon footprint and help the M&E sector achieve net zero, i.e.: “when the amount of carbon emissions associated with a building’s embodied and operational impacts over the life of the building, including its disposal, are zero or negative” (UK GBC, 2019). Additionally, onsite manufacturing may cause noise pollution and local disturbance – whereas taking it to offsite keeps this at a minimum, which is particularly beneficial when construction takes places in a residential area.

Winner: Offsite

Cost

Taking all of the aforementioned elements into account, you may have concluded that offsite construction is also the more cost-effective option. While on the surface it may seem like onsite construction would be cheaper because no ‘new’ steps need to be taken and because of the upfront offsite costs for developing a factory, when you factor in the reduced labour, transport, material waste, and number of deliveries, and not having to hire specialist workers, as well as other points, these all contribute to cost-saving in the long run.

Winner: Offsite

So, onsite or offsite?

Which one is best for you? Hopefully, the breakdown will help you decide what’s best for your individual needs. It all comes down to your personal priorities. If your priority is to start a project as soon as possible, for example, or if the size of the prefabrications are too large, then onsite is the option for you. Whereas, if the initial cost and planning is not an issue for you, offsite manufacturing is most likely the overall best alternative due to its versatility and effectiveness.

Although offsite solutions have started to become more mainstream in recent years as more are starting to see its benefits, onsite manufacturing is still the ‘go-to’ method – largely due to the fast-paced nature of the sector and the fact that it doesn’t generally engage early in projects. However, it also comes down to outdated perceptions and the lack of desire to change traditionalist methods, as well as to invest some money initially, despite the long-term savings it would result in. If these can be overcome, offsite manufacturing can really be revolutionary for the construction industry.

REFERENCES

Designingbuildings.co.uk. 2016. Modular vs traditional construction. [online] Available at: <https://www.designingbuildings.co.uk/wiki/Modular_vs_traditional_construction> [Accessed 28 February 2022].

GOV.UK. 2021. Golden thread: factsheet. [online] Available at: <https://www.gov.uk/government/publications/building-safety-bill-factsheets/golden-thread-factsheet#:~:text=The%20golden%20thread%20is%20both,and%20is%20up%20to%20date.> [Accessed 28 February 2022].

Miles, D., 2019. Offsite construction: advantages in costs and efficiency. [online] Atamate.com. Available at: <https://www.atamate.com/atamate-blog/offsite-construction-advantages-in-costs-and-efficiency> [Accessed 28 February 2022].