How does BIM work, like really work, in the real world?

There are a proliferation of diagrams with arrows and graphics invariably arranged in a circle,

or as a seamless flow.

But none of these are explanations of how BIM actually works, they are blueprints of how the authors think BIM should work.
It is an attempt to promote the myth that “BIM is about process, not technology”, so that you will use the standard, guide, paid advice or academic career being pushed.

BIM does involve some new and different processes, but try doing it without technology. It would go from being a highly efficient process to one that involves an enormous amount of  work and time that is error prone and tedious. Basically the benefits would evaporate.

The reason those of us that use BIM do so is for the efficiency benefits, both in time and accuracy. And as each of us has different deliverables and responsibilities we use BIM in distinctive ways, using the different “technologies” available to us. These “technologies” limit what we can do, and as it advances, we change the way we do things. To those of us working in the real world it is technology that drives the process.

But all that doesn’t matter. The original meaning and purpose of BIM (see my post on this issue) was that each player in the process used BIM to do their job more efficiently. The fact the information generated doing this could be easily provided to others was a bonus, not the purpose of using BIM in the first place.

Rather than do another diagram I thought I would try and describe the different BIMs that are happening in the construction industry now. There are sub-BIMs I haven’t mentioned, some of which with new technologies may grow into full BIMs.
An example is Costing BIM. Quantity data can be extracted from design and construction BIMs to assist costing, but currently a separate Costing BIM, or cost model, is not created. That may change if (or when) cost estimating includes future operational costs. A separate cost model would be required as neither the design professionals nor contractors include this data in their models, their expertise and responsibilities are in building creation, not building operations.

I’ve counted four major types of BIM in current use.


Survey BIM is the creation of a virtual model of what already exists.

It is very new field as advances in technology make it economic, with new players entering the field. Traditionally design professionals have modelled existing conditions, but one would expect Land Surveyors to become the main creators of survey BIM.

The deliverable is an virtual model of existing buildings, services and terrain, which can be used by design professionals for new works, or by facilities management as the basis for FM BIM.

Technologies like drones and laser scanning are used to gather data, but a Survey BIM is more than gathered data. This data is used to create a virtual model of intelligent objects.
Currently software used is the same that design professionals use (see below) as the functionality required is similar. There is the potential for much of the process to be automated, although I doubt it will ever be fully human free. Design professionals and facility management require simplified virtual models, which will always require some judgement.

A Survey BIM will only contain what has been requested. Although a lot information may be gathered, it is still not absolutely everything, nor is all data gathered necessarily included in the virtual model. The reality is, and always will be, that it is uneconomic to create a virtual world that exactly matches the real world.
Therefore the contents of a Survey BIM will vary depending on the purpose it is commissioned for. One done for alteration works is unlikely to be useful for an FM BIM, and one done for FM unlikely to provide all information required by design professionals for alteration works.


A Design BIM is started when the need or desire for a building (or facility) is turned into something that can be built.

It involves design professionals – architects, engineers, cost consultants.
Contractors, facility management, and others may provided advice, but they are not responsible for the contents of design BIMs.

Deliverables include sufficient information to describe design solutions, to construct the building, and cost it.

BIM is used at this stage to create virtual design models. The main purposes of these models is to create a representation that can be tested – used for various analyses, from structural, cost, energy use, to visualization.
Most BIM software can also generate traditional deliverables from the model, (drawings, schedules etc.), and is currently the most common use for design BIM.

Software that is used to create design BIM models requires certain functionality to be useful for design purposes. Changes must be easy to make, and those changes must propagate throughout the model. Not all design decisions can be made at once so there needs to be the ability to “placehold’ information. And there may be more than one design solution in play at any time.
Typical software currently in use includes Autodesk Revit, ArchiCAD, Tekla, Bentley, Nemetschek.

It would be reasonable to expect a design model to:

  • have all elements critical to the project’s construction modeled.
  • that those elements are consistently categorized (eg identifiable as walls, floors, doors etc.)
  • materials used in those elements are consistently categorized

I’ve used the weasel words “critical” and “consistently” because the actual requirements will depend on which particular standards (and there are many) are used, and what specific deliverables are being paid for.

All this is only to the extent required to satisfy the deliverables and responsibilities of the model authors. What is crticial is that what is provided is consistent within itself, and that the data in the model is the same as other deliverables from the same author.

If available a Survey BIM may be included or form the basis of a Design BIM. But generally Design BIMs are where project BIM models are initially created, and become, or form the basis of, most future BIM models.

It is important to keep in mind what a design BIM is created for. That it is created for the authors’ particular purposes, not for the future use of others. Its use to others is limited to extracting  information useful for their particular purposes.


A Construction BIM model is used to organize the construction of a building (or facility).

It involves the head contractor and their subcontractors – particularly if they provide shop drawings andor designs.
Design professionals may be involved, but only to the extent the design is changed, or if they are providing services directly to the contractor (e.g. Design & Construct contracts). In any case it is the contractor who holds responsibility for Construction BIM.

The ultimate deliverable is a completed building, BIM merely assists the process. Although there may be an As-Constructed deliverable in the form of a BIM model.

BIM is typically used during construction to assist processes: installation coordination, setout, time scheduling, cost control, safety management. A BIM model is increasingly being used as a location coordinator for everything, from task allocation to defect rectification.

A construction BIM makes use of Design BIMs. The various design models are combined to create a single model representing the complete building (or facility). More detailed models from subcontractors are included, as well as representations of construction equipment and facilities like cranes and site sheds.
Typical “federating” software includes Navisworks, SoIibri and a growing number of web based solutions. There are also other specialist software that can plug into these to do specific tasks, like costing, defects tracking etc.

A Construction BIM model is not really a model as much as an aggregation of models. Data can be extracted and new data associated with elements within this aggregation, but no changes in the underlying models can be made. Only the providers of the original models can do that (hence the continued involvement of design professionals).

At the completion of building works the construction BIM model is still made up of other models. It also contains information of no further use, like time scheduling data and resource allocation.

In theory a construction BIM model could provide the basis for a facility management BIM model. But this relies on available software. To my knowledge none of the currently available BIM federating softwares can provide automated exports suitable for FM, that is, exports that don’t require major manipulation and auditing. This is an area I am sure we will see technology providing new opportunities for BIM processes, but at the moment it falls short of any of the BIM utopias we read about.


The last BIM is the FM BIM which is used as a visual database of the things that are managed during the operation of a building (or facility). Rather than data being in text documents and spreadsheets it is linked to a BIM model where it can be found by looking through this virtual model.

The FM BIM model is for the facility managers of the building, not just the ones around when the building is complete, but all future facility managers. This differs from the Design and Construction BIMs which are only useful for a limited time, and therefore can be less rigid as whoever set the model up is still around to ask questions.

An FM BIM model needs to be a static model. A virtual model of what is – not what is to be, (which is what Design BIMs and Construction BIMs are).
The contractor, and sometimes design professionals, role is limited to providing the BIM information they have created for their own purposes. Relevant information is re-purposed from this data to populate the FM BIM model.

There is information not in the design or construction BIMs that needs to be added to an FM BIM. Maintenance manuals, warrantee information etc. supplied by subcontractors as part of their contracts. This data is generally not required for design or construction so is provided just before, or even after, construction is completed.

Besides removal of redundant data an FM BIM needs to be simplified. There is no point graphically representing something if the FM team have no method to update those graphics. It is better to link lots of text data that can be easily updated to major objects. For example it is easier to change data if the lock data is part of whole door rather than represented by a separately modelled lock that has to be remodelled to reflect the change. Note that many FM BIM systems do not have a method to update graphics, for example systems based on IFC (see my post on IFC).

Timing of the creation of an FM BIM is critical. If it is not created during the last stages of construction so it is ready when the building opens the data provided by the design and construction team may be out of date by the time the FM BIM is usable. For example things like equipment replacements due to failures, or commissioning changes due to things discovered after occupancy. There may be few differences, but without doing a complete audit no-one could tell – which defeats the purpose of using design and construction BIM information in the first place.

The deliverable for FM BIM is an integrated data repository of information required to manage the building (or facility). There is little to gain by having only some information in the FM BIM, its purpose is to unify data to make it easy to find and avoid duplication. There is little point having a whole lot of information that is not needed, or included “in case” it will be required. The more data the more work to keep it all up to date,. The amount of data should be based on the resources available to maintain it, not the amount of data available.

One of the ideals of BIM is to eradicate the work required to re-purpose information for FM uses. But as can be seen by what is involved in Survey, Design and Construction BIMs there is a lot of information not required for FM, and information that is useful is structured for purposes other than FM.

Data from an FM BIM may be useful for future Survey and Design BIMs, but an FM BIM is not adequate to simply become either of those BIMs. To do so would mean carrying and keeping up to date all the extra information those BIMs require for the life of the FM BIM.


BIM is a fantastic technology, it allows us to engage in new, more efficient processes. But it is important to remember it is being driven by individuals harnessing BIM for their own purposes.

If we concentrate on what people are actually doing, supporting each other’s workflows, rather than fantasizing about a Utopian future built around theoretical processes, BIM will come to dominate naturally as the preferred way of working. Without the need for it to be mandated, by government or big business, with the loss of control over our destinies that entails.

The post Different BIMs for different Purposes appeared first on ConvertBIM.


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