Why Engineers and Architects Should Use 3D Building Models
Posted on 13th July 2021
Categorised as architecture, bim, cad

Why are 2D drawings still so popular?

To most architects, engineers and other professionals in and around the construction industry, the use of drawings is innate and fundamental. In any discussion about a potential idea or project, the first thing that we do is reach for pencil and paper to explain what we are thinking more clearly. The adage ‘a picture is worth a thousand words’ is especially true here.

Although the earliest examples of architectural drawings can be traced back to Mesopotamia at around 2200 BC, it was not until the Renaissance period that the use of drawings to set out details of construction projects started to come into common use.

Here in Britain, Inigo Jones (1573 – 1652) is widely acknowledged as the first architect to draw up his designs, leaving behind a legacy of many notable works including the Queen’s House at Greenwich, one of the Royal Museums Greenwich estate which includes the Cutty Sark, the National Maritime Museum and the Royal Observatory.

The use of 2D drawings in architecture and engineering spread across the professions and, although the equipment for producing them became elaborated, until the early 1980s, most drawings were still produced by hand, on drawing boards using pens, pencils, set squares, parallel motion bars and the like.

This can be seen in pictures of design offices of the time, where tens or even hundreds of engineers and technicians would be working away on projects such as the Concorde supersonic airliner and the Apollo space programme.

3D Building Design

In the field of architecture, the Italian architect Filippo Brunelleschi (1377 – 1446) created physical models to test and validate that his projects could be built, that the techniques he proposed to use were viable and to serve as templates for the masons who would construct the buildings. He also used them to control the progress of the works. In 1418 he famously won the competition to build the new dome for Florence Cathedral with the help of a scale model made of brick.

It was another Italian architect and all-round polymath, Leonardo da Vinci, who embedded architectural model making at the heart of his work. A firm believer in the purpose and intentions of model making, Da Vinci created many of the architectural patterns and theories that remain in use today.

In the field of engineering, John Smeaton (1724 – 1792), in England, was the first man to call himself a ‘civil engineer’ although he began his career as an instrument maker. He is most famous for constructing the third Eddystone Lighthouse on the dangerous Eddystone Rocks, 9 miles (14 km) south of Rame Head in Cornwall.

Unlike its two wooden predecessors, Smeaton’s lighthouse was constructed from interlocking masonry, a skill he had developed during his time as a craftsman. It is a tribute to Smeaton that his lighthouse was operational from 1759 until 1882, when it was decommissioned and rebuilt on Plymouth Hoe, where it remains in place as ‘Smeaton’s Tower, a tourist attraction, to the present day.

Taking inspiration from the interlocking kerbstones of London streets, together with the shape of oak trees, with their wide, stable bases and waisted trunks offering the least resistance to the elements, Smeaton made models of his proposed structure to test the viability of his design and construction methods.

No doubt Smeaton sketched drawings as he was developing his 3D model and ultimately produced a set of drawings to place in front of the commissioning client, Robert Weston, to gain approval and funding. He also produced working drawings for his assistant engineer and the team of masons working on the construction.

Another example of the use of 3D physical modelling can be found with the design and construction of the Britannia Bridge across the Menai Strait in North Wales.

Designed and built by the renowned engineer Robert Stephenson, the proposed design for this railway bridge was six times larger than any girder bridge previously constructed and represented the greatest increase in span in the history of bridge building.

Stephenson turned to ironmaster William Fairbairn for advice. Fairbairn agreed to undertake a number of experiments to provide confidence that this never before attempted feat could be achieved.

Fairbairn undertook several dozen tests on reduced-scale models made of wrought iron both to determine the best cross section for the wrought-iron girder and to achieve the greatest strength-to-weight ratio for the 140m span, thin-walled tubular girder bridge that would also avoid fracture in tension and buckling in compression.

With Fairbairn’s assurance, Stephenson eventually designed a bridge consisting of twin rectangular iron tubes running through three masonry support towers, to abutments at either end, without any further bracing or suspension.

The use of 3D physical modelling in architecture and engineering therefore goes back to a time before even 2D drawings came into common use for the expression of design intent.

In recent times, these 3D physical models have typically been constructed from wood, card, plaster or similarly easy-to-work materials, to give a scale representation of the proposed project and to test whether the design will meet the demands of:

  • Working as planned
  • Looking as envisaged it will look
  • Its environmental context
  • Practicability of construction

Such models still have their place, providing a sense of the aesthetics and proportion which can be difficult to realise from 2D drawings alone, especially for stakeholders not used to looking at technical drawings.

However, they are labour intensive and time consuming to build; there are also limits on what can be achieved with them. For example, it is not possible to take a cross section through the model without either cutting it or constructing it as a sectional view to start with.

What do we learn from 3D?

The examples above demonstrate that, as our predecessors knew, we live life in 3D,  we usually conceive our designs in 3D and model and prototype in 3D. In other words, the replication of our proposed design as it will finally exist is crucial for our understanding as to whether our project will satisfy the requirements of the brief we have been given by the client.

The reduction of a 3D concept or 3D building design to 2D drawings is merely for convenience, as a means of easily transmitting information to other professionals involved in the design process.

Until the advent of widespread, powerful computing, 3D prototyping meant physical modelling to scale or the creation of full-size mock-ups, as it did with Brunelleschi, da Vinci, Smeaton, Stephenson and Fairbairn. Actual physical prototyping still has its place today but it is expensive and time consuming and, with the advent of computerised digital prototyping, a viable alternative is available.

The rise of CAD

The biggest change in design offices came about in the 1980s, with the rise of the 32-bit workstation computer (e.g. Apollo, HP, Sun Microsystems, Silicon Graphics and others), swiftly followed by the PC.

These devices were interactive, unlike the mainframes, and allowed computer power to come out of the computer room and be installed on a designer’s desk. They gave rise to a plethora of early CAD systems, many of which have now fallen by the wayside.

There was a distinction made between Computer Aided Design (3D) and Computer Aided Draughting (2D). Many of the systems on the more powerful 32-bit workstations were 3D solid modelling or surface modelling packages, finding favour in the aerospace, automotive, oil & gas, process and, more slowly, in the manufacturing industries.

The construction industry, always more traditional and more conservative, was far slower to change and adopt 3D CAD. It did however, take up 2D CAD for drawing production with more gusto, most likely because the upfront investment costs were much lower and the return on that investment by way of consulting fee income more rapid.

The move from drawing board to 2D CAD software running on a PC was also a simpler proposition in terms of working practices. It simply provided an electronic medium on which to essentially carry out the same task but with the added benefit of being able to re-use CAD elements from one drawing in another and much faster edits and updates. But, at its heart, a 2D CAD drawing was still essentially a linework drawing.

That simplicity of approach, the persistence of custom and practice, familiarity, short learning curve and modest investment and maintenance costs mean that 2D CAD draughting remains extremely popular, especially in the architecture, building and construction industries. Not so much a case of ‘knowing what we like’ as ‘liking what we know’.


3D modelling and 3D CAD had been with us since the 1970s but used primarily in industries such as aerospace, automotive, oil and gas etc. In these industries, the investment in the then necessary hardware (a mainframe or high-end mini-computer) and complex application software was high and the 3D modelling and numerical analysis used primarily for safety-critical applications or high-specification manufacturing where the substantial up-front investment costs could be justified.

In the construction industry, 3D modelling was most often used for structural applications e.g. in bridge design, multi-storey frame design or complex structural forms (think Sydney Opera House) where again, safety of the proposed design was of critical importance.

As the 1980s gave way to the 1990s, the PC became more powerful with the result that the 3D CAD systems previously confined to expensive 32-bit workstations could now be ported on to much less expensive hardware.

Over the next few years, the price of powerful 3D CAD software tumbled in response to greater demand and competitive pressures.

CAD industry consolidation continued and the Revit software, originally developed by Charles River Software, emerged in the late 1990s and was acquired by Autodesk in 2002.

Conditions were now in place for much more widespread uptake of 3D building design and the use of 3D BIM modelling software to facilitate it. Software and hardware was far less expensive than had hitherto been the case, with product now widely distributed and supported by the software vendors and their local representatives.

In the UK, as around the world, the largest firms working on multi-disciplinary projects with multiple subcontractors have led the charge, driven by the need to improve quality and the sheer cost and consequences of sorting out errors on-site which could arguably have been foreseen and eliminated at the design stage with a 3D approach. The value of 3D BIM modelling a complex building and coordinating inputs from multiple subcontractors to resolve clashes and other issues before work commences on site cannot be overstated.

The UK Government saw the value of this approach and in 2011 set out “The Government Construction Strategy”, a policy paper which set the target of reducing the cost of government construction projects by 15-20 percent by the end of the then current Parliament.

One of the key initiatives arising from that policy was to mandate “fully collaborative 3D BIM Modelling by 2016” which means that anyone or any firm now involved with a government project in the UK is contractually obliged to use BIM.

The use by leading firms in the industry combined with a Government mandate has provided increasing pressure on firms to adopt.

Progress is accelerating but the uptake of 3D BIM modelling, 3D building design and 3D visualisation is not as fast or as widespread as the protagonists would have hoped for. Why is that?

The answer to this question is not easy and a number of factors are at play:

• The innate conservatism of the construction industry. Reluctance to change well established ‘custom and practice’.
• The business model used within the industry, especially among small and medium sized firms of architects and consulting engineers. These tend to be fee-driven for immediate income rather than investment-led. Most will not change unless and until they are forced to by the requirements of a particular project or a particular client.
• Lack of education and awareness. Although most have heard of ‘BIM’, many are still unaware of what it can do. There is also an innate scepticism among many as to whether it will bring the much lauded benefits. This scepticism is not entirely unjustified given the hype which typically surrounds the software industry.

3D Visualisation example

The 3D visualisation below is a good example of when and how 3D BIM Modelling and the creation of 3D building drawings can come into their own.

One of our clients, a designer and builder of luxury swimming pools – let’s call them Jones Swimming Pools – came to us with a small problem: how to show their client that their design for the pool that they had proposed would actually work in terms of the planned steps down into the pool and jacuzzi area.

Our client carries out most of its projects using a 2D approach in AutoCAD which, for the most part, serves them extremely well in time honoured fashion. They know what they can produce and how quickly they can produce it.

Sometimes Jones gets involved in larger projects where they are required to coordinate their design with other project participants in a much larger project managed by a main contractor and where a 3D master BIM model is being used.

The conversion of the old Canadian High Commission offices at 1 Grosvenor Square, London was just such a project. Managed by Mace for developer Lodha, Benchmarq provided 3D BIM project services for our client ‘Jones’ in order to integrate the water supply and filtration pipework and associated equipment for the basement pool into the master Revit model being managed by Mace.

See https://www.lodhaluxury.com/no-1-grosvenor-square

For the small pool example above, where they needed to show their client how the design for the pool and jacuzzi steps would work, a couple of 3D visualisations are shown below.

We have also included a link to ‘Sketchfab’ where this simple model can be viewed and manipulated in 3D by anyone through their Internet browser:


3D Bim Model of a Swimming Pool

When should Engineers and Architects Use 3D Building Models?

The answer to this question really depends on need and whether your firm wishes to embrace 3D building design or not.

Having worked with 3D BIM modelling software for many years here at Benchmarq, it is clear that it is not something that can be picked up and put down occasionally.

Moving to the use of 3D building design software demands commitment, certainly not as much commitment financially as was necessary in the past, but commitment in terms of learning and implementation.

These essentially are opportunity costs: the cost incurred from loss of time which could be otherwise be more productively utilised by continuing with current methods.

The ultimate prize is competitive advantage, with the ability to participate in complex projects offered out by industry leading firms, to establish a reputation for quality and to reduce the incidence of errors arising from translating 2D drawings into 3D reality.

But, before we get carried away with further hype, let’s consider the situation from a sober viewpoint:

For those who have yet to dip their toe into the 3D building design water or for those who do not think they are yet experiencing enough demand for 3D, Benchmarq can provide a solution with its project services. We regularly work with clients who cannot yet justify employing an appropriately skilled technician and investing in the required hardware and 3D building design software. For those that decide to allocate one of their current staff, consideration also has to be given to training and getting the first few projects under the company belt. Benchmarq can help in all of these areas:


We work with a number of survey partners and can commission measured building and topographic surveys of your projects, bringing the data back to our skilled team for the creation of the 3D BIM model and 3D building drawings. We can also extract 2D drawings from the 3D BIM model should you wish, handing the whole output package over to you as a deliverable.


We also have plenty of experience of taking 2D CAD drawings and converting them into a 3D BIM model, usually for the purpose of coordination with a master BIM model being managed by a main contractor for whom you are acting as a specialist subcontractor. We can liaise and coordinate the 3D BIM model with the main contractor and other participating subcontractors on your behalf.

CAD services

For those who would rather focus on their specialist, higher-value design activities, we can also assist by providing 3D BIM modelling and 2D CAD drawing production services, allowing you to focus on what you consider to be your core skills but nevertheless still being able to deliver all the contract documentation which your clients require.

Finally, for those who already have made the move to 3D building design, we can assist by providing additional capacity on larger or more complex projects; also by providing specialist services such as the development of bespoke Revit families or high quality 3D visualisation services to produce stunning imagery, stills or movies, and construction infographics.

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