Offsite construction + prefabrication in a BIM context – exploration

Offsite construction is often lauded as the future of efficient building, mentioned in the same breath as BIM (building information modelling) in countless architectural publications.

What do the statistics show about market adoption? According to recent data there will be a projected 6.5% annual increase in prefabricated construction projects in the US (2022-2030), whereas in countries like Sweden, 84% of detached homes already use prefabricated timber (with much lower scores of 5% in countries like the UK). This data shows a big disparity in embracing prefabrication (especially timber), highlighting cultural differences in construction. As a global company with users around the world, we see this played out in how our users use our software and what features they request.

Let’s take a closer look at some of the benefits of prefabrication, where BIM software comes into play, and what you should expect when embracing modular construction.

The benefits of offsite building

Offsite construction is essentially the practice of building with prefabricated components – building elements such as walls and roof elements are prefabricated in a factory and then assembled at the building site. It’s efficient, cost-effective, and lowers the environmental impact of building. But it is also very material dependent and requires new skills and workflows in order for it to be successful.

What are the main benefits of offsite building?

It depends on the scope of the project, building materials, and the assembled team, but here are some of the common offsite benefits:

  • Efficiency due to a more streamlined process
  • Less errors as there is less hazardous site assembly
  • Productivity benefits from building in a more structured way
  • Reduced environmental impact
  • Safer and more secure building sites
  • Quality control is easier
  • Lower costs due to bulk purchasing and less risky assembly
  • Shorter build times
  • Creating extensions and recycling materials is easier
  • Better supply chain management.

Using prefabricated elements improve the jobsite experience as they mean that people on site have less to assemble. Nowadays, building elements such as walls can be finished to a very high standard in a factory, including painting and adding in important structural features and small engineering details.

In order for prefabrication to really work, there needs to be a lot of collaboration between all the different phases of the project and the teams involved. Building in this way can be challenging when making the transition. In order to get started, a lot of teams embrace offsite in a hybrid way, using parts of the prefabrication process.

Prefabrication and software – leaner ways to build with BIM?

We’re very proud to be part of the BIM revolution as an Archicad add-on; the arrival of BIM and concepts such as digital twins and lean construction dovetail with the prefabrication trend.

Modular construction methods place more emphasis on element production and preparing buildings in factories. This requires data and software to be harnessed in a more strategic way, as a lot of emphasis is placed on the modelling phase. This is where software really comes into play as the ability to model and mass produce relies on accurate drafting. Using software to create 3D models, automate calculations, and produce elevations enables prefabrication accuracy. (We’re always looking for ways to improve our drafting processes and automate key workflows).

Another way in which software intersects with prefabrication is in its ability to improve collaboration between different parts of the project. One of Archicad’s most important benefits is the fact that the software enables one file to travel across the entire drafting to construction workflow, keeping the data secure and consistent across the building lifecycle.

Mass timber and prefabrication

As shown by the stats in Sweden, prefabrication and timber are a great match. The fact that timber is readily available and relatively easy to mass produce using CNC (computer numerical control) machines makes it ideal for building in a modular fashion. (For example, users of ArchiFrame are able to export their timber models directly into CNC code, and many element factories in Finland, Sweden, and Norway are using these functions to automate production). 

And now, the ability to use mass timber elements in prefabrication means that larger and larger buildings can be built in this way. Especially in the Nordics, there is a lot of innovation when it comes to building in CLT (cross laminated timber) and other forms of mass timber. (Our software, ArchiFrame, includes CLT workflows).

An example of innovative timber products are the Kerto LVL mass timber elements from Metsä Group that are ideal for modular construction. It is worth exploring the possibilities of timber, especially when it comes to structural elements. 

Prefabrication and housing

You will often hear it said that prefabrication is the solution to getting new housing built cheaper and more efficiently, but an emphasis on standardisation also has its drawbacks. 

Prefabricated houses can definitely be a solution to tight schedules and labour shortages, but we should also keep in mind that the ultimate end goal should be to create livable, safe, and fit for purpose housing.

A lot of prefabricated house designers are creating innovative and interesting designs to showcase what can be achieved with this method.

What to keep in mind with modular construction

There are some good points in this recent article from Building Design + Construction about what you will need to keep in mind when using prefabricated methods. Skilled 3D modelling is needed to ensure design fidelity and good software is only part of what will help you achieve that. Solid processes, training, and documentation are essential for great BIM projects.

Make the most of offsite methods by embracing the bulk purchasing of construction elements to bring down project costs. This is all part of a gradual shift from projects to products as the new industry of modular architecture takes off.

Be aware that the logistics of this will be different, and that different skill sets and personnel will be needed to ensure project success. With a method like this, there is less flexibility when it comes to design changes, so it’s important to do a lot of modelling in pre-production.

Materials are another big factor in determining whether prefabrication is suitable, though prefabrication is being used pretty widely from timber to concrete.

What do you think is the most important benefit of offsite construction and BIM adoption?

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