BIM Frequently Asked Questions

Just getting acquainted with BIM or looking to round out your knowledge? You'll be sure to learn something from reading this list of ten.

This content was adapted from an article by Dr Stephen Hamil, Director of Design and Innovation and Head of Building Information Modelling at NBS.

What is BIM?

BIM stands for "Building Information Modelling" or a "Building Information Model". This is a rich digital model of a physical building. This model can be used by the design team to design the building, the construction team to model the construction of the building and then the building owner to manage the facility through its life.

Who owns the BIM?

To maximise the full benefits, the building owner must own the BIM.

If an engineer, for example, creates a BIM and does not share it, then the true benefits are not realised. For example, the designs across the design team will not be fully coordinated, the construction team will not have the chance to model the construction process digitally (or have to re-key the information to do this) and the building owner will be left to manage the facility with boxes of paper documents.

To maximise the full benefits the design team must share their information model, pass this to the construction team and then place in the hands of the building owner.

A very simple analogy would be to compare BIM with commissioning a book or a photography session. If the client only received a physical book or prints at the end of the process then that would be satisfactory, but receiving the digital content for the book or the original digital photographs is far more valuable. The client can reuse this content in future and get much better value out of it.

Who will make the most money from BIM?

We can ask a very similar question about when the industry moved from drawing boards and typewriters to the first CAD and word processing systems in the 1980s. The answer is everyone made money because the work processes became more efficient and accurate. If you made a mistake you could undo it. If you had to draw the same window 100 times, each copy was exactly the same as the first. If you wanted to find a particular word or phrase within a 100 page document, you could search for it in seconds.

Now it is time for the industry to move to the next stage of technology and structured data.

The designer will no longer spend time retyping the data from a 2D CAD model into Microsoft Excel to produce a 200 instance door schedule, and they will not spend time going through a 150 page specification looking for each place they have requested the contractor to submit proposals or samples. The contractor will no longer be informed about clashes in the design by the structural and M&E engineers on site during construction, and they will be able to more efficiently price projects by getting more competitive prices when purchasing in bulk, with less waste. And finally, the building owner will be able to manage and alter their facility using an accurate digital model of the physical building.

What are the legal implications of BIM?

For all of the positives associated with BIM, there are also some uncertainties, and the legal questions of BIM as a contract document is one of these.

For a number of years contract documentation has all been on paper. In recent years this has started to turn digital, with PDF being a common medium. We are fortunate that PDF is quite a simple, robust, data format. But consider the example of a contractor referring to the contract specification for the colour of the façade; the specification refers to the drawing. When the contractor views the drawing in their chosen PDF viewer this façade is red. However, the designer has changed this to be blue but not coordinated this across the documents. Who will pay the bill for this mistake?

This problem is far more likely to occur if a BIM was to be used for contract documentation. As an interoperable data format, a BIM is a far more complex and far less mature than a simple 2D PDF. What if the model opens differently in the software the contractor is using and this has potential financial or health and safety consequences? Who would pay the bill for this mistake?

A recent article in JCT News discusses this very subject. They suggest that collaborative contracts such as JCT Construction Excellence, NEC3 or PPC2000 could be readily adapted to a "full" BIM process. These could potentially allow risks to be identified and the process managed closely.

Is the UK falling behind the rest of the world on BIM?

There are certainly some very strong case studies in the USA and a number of Scandinavian countries. It has been adopted most in countries where the government have insisted on the use of BIM on certain projects. In the UK, NBS surveyed the industry at the end of 2010 and nearly half of respondents were not aware of BIM. However, later in the survey, it emerged that those that were aware of BIM were making steps to adopt it on projects in the near future. 25% of those aware of BIM said they would adopt in on the majority of their projects within a year. 50% of those aware of BIM said they would adopt in on the majority of their projects within three years.

2010 did seem like a year where BIM adoption accelerated in the UK. Big clients like Asda and Gatwick Airport are insisting on the use of BIM and the UK government, through Paul Morrell, are suggesting that all government funded projects over a certain size will soon have to use BIM.

How will industry help BIM adoption happen smoothly in the UK?

More and more, big clients with millions of pounds worth of facilities to manage will start to insist on the use of BIM, "If you don't use BIM and hand over a digital model to us as a record of our building, then you won't work for us". It may sound harsh, but if they are paying the fees then they have the right to insist on this.

Equally though, it is down to the senior members of design practices to educate their staff on BIM, train them and to invest in this process. These are the same professionals who made the CAD and the word processing revolution happen in the 1980s. They must now recognise that the construction industry is changing again and prepare to adopt BIM.

Finally, software vendors and data providers (such as NBS) must make BIM happen "under the hood". Well-structured data and intuitive software will help the transition and lower the training costs.

Is there a single BIM or many BIMs?

One day there will be a single BIM. This will be created when the client is briefing the design team. All project members will work on this single shared BIM through the lifecycle of the building. For more information on this concept see the website

However, this technology is in its infancy. In the near future, it is more likely that there will be a number of BIMs and that data from each will interoperate. Each designer will have their own CAD and specification models. The data from each will come together at key milestones to allow costing, quantity take off, performance analysis and clash detection. Finally this data will all be exported to a non-proprietary data format such as COBie2/IFC for handover to the building owner.

The current focus should not be on taking the innovators or the early adopters to a "holy grail" of a single BIM server, but to get the majority of the industry to adopt the key advantages of BIM.

Is affordability an issue and how can smaller practices be persuaded that BIM is a worthwhile investment?

We once again return to the CAD/word processor analogy of the 1980s when the same discussion took place. People asked whether they could afford a personal computer and the CAD package. Similar questions arise with every advance in technology. Will every home have a personal computer? Will every home have the internet? Will every person have a mobile phone?

Arguably it an easier investment for smaller practices as they can be more fluid in their business decisions and can modify their processes more easily. Within a larger practice with hundreds of professionals it is a harder to adopt new processes.

However, in 10 years (or maybe only 5 years) I suggest people won't even talk about BIM. It'll simply be part of how the construction industry works.

How do master specification systems fit into BIM?

Master specifications will provide the detailed information, the "I" in building information modelling.

They will describe in detail the same objects that are visually represented in the CAD model. So within the CAD model you will be able to see how many windows you have, where they are located and what they look like. In the specification model the information behind the window will be recorded, what regulations/standards the window must comply with, what workmanship/execution tasks are required, what manufacturer products make up the window and, finally, what regular maintenance is required through the window's life.

It is key that master specification systems raise their game and invest in improving their data and their software so that the full benefits of BIM can be achieved.

It is key that master specification systems and CAD systems interoperate so that this information can be shared and used to its best effect.

What is the alternative? That all of this information goes into the CAD objects and that each practice maintains their own libraries? Over 200 key reference documents change each month. Who will research and maintain these CAD libraries to ensure best practice?

This is why BIM is revitalising master specification systems. It is now the job of master specification systems world-wide to enhance their data and their software to allow their users to make the most of BIM.

How do cash and carbon fit into BIM?

BIM will allow costs — both capital and environmental — to be considered much earlier in the design process.

A client will be able to put budget costs against the major elements of the building and set targets the design team must work to, such as capital cost, embodied carbon, waste management and life cycle running costs. This information will go into the BIM prior to the CAD software even being opened.

When selecting systems, for example comparing a clay brick wall to a natural stone wall, the likely cost impact will be indicated against these budget constraints. As the systems are fully designed these budget estimates will be more fully resolved.

At tender, the contractor and subcontractors will be able to price work packages accurately off the single model. Finally, an as-built fully-costed building information model will be passed to the building owner on completion.