Building Information Modeling
A Framework for Collaboration

Howard W. Ashcraft

I. Overview

Building Information Modeling technology has arrived and is being used by designers, contractors and suppliers to reduce their costs, increase quality, and in some instances, achieve designs that would be impossible without digital design and fabrication. Pilot projects have been completed where the entire structure was built using CNC[1] fabrication driven from the design model.[2] And as the technical issues of standards[3] and interoperability are addressed, the software capabilities will develop further.

The legal and business structures for Building Information Modeling, however, lag far behind. BIM’s implications are just being realized and few solutions have been developed. Moreover, liability concerns have lead practitioners, and their attorneys, to contractually wall off the building information model—thus depriving the model of its greatest benefits.

Building Information Modeling is more than a technology. Although it can be used without collaboration, such use only scratches the surface of what BIM can achieve. Because the model (or models) is a central information resource, it leads naturally to intensive communication and interdependence. Building Information Models are platforms for collaboration.

But collaboration is not a construction industry hallmark. Rather, the industry, its practices, and its contract documents assume definite and distinct roles and liabilities. The insurance products used by the construction industry mirror these lines of responsibility and liability. But collaborative processes, and BIM in specific, foster communication, joint decision making and interdependence that blur the distinctions between parties. Technology and business practices are in collision.

BIM also collides with traditional professional responsibility principles. Although virtually all professional licensing regulations require that designs be prepared by a person “in responsible charge,” much in a collaborative design is not supervised or directed by a single person or entity.

Change is required and change is coming.[4] This paper discusses attributes of BIM that conflict with traditional notions of responsibility and proposes alternative business and legal structures that support using BIM in a collaborative environment.

II. Building Information Modeling: Definition and Characteristics

Building Information Modeling (BIM) broadly encompasses a series of technologies that are transforming design and construction. In essence, BIM uses information rich databases to characterize virtually all relevant aspects of a structure or system. In a BIM system, the model simulates the structure. Drawings, specifications, take-offs, and even construction details are not separate documents, but specific manifestations of the model.

As defined by the National Institute of Building Sciences, BIM is:

A Building Information Model, or BIM, utilizes cutting edge digital technology to establish a computable representation of all the physical and functional characteristics of a facility and its related project/life-cycle information, and is intended to be a repository of information for the facility owner/operator to use and maintain throughout the life-cycle of a facility.[5]

Because all aspects of a project are driven from a single database or related databases, issues of drawing coordination and conflict errors are greatly diminished. Integration of information from multiple disciplines also supports project visualization, simulation, and optimization. The model can even be used to drive computer-controlled fabrication tools, leapfrogging the tedious and error-ridden shop drawing process.

A. Parametric Modeling

Parametric modeling is the basis for BIM processes, and in contrast with the polygonal model[6], the parametric model is data rich. Although a parametric modeling system can create 3D visualizations, the model is not constructed from simple graphical elements. Instead, it is generated from a relational database containing information regarding attributes of a structure’s elements and the relationships between them. Fixed or flexible ties can be made between elements allowing the model to either maintain or adjust elements in response to design changes. In addition, the model can be used to generate space calculations, material take-offs, energy efficiency analysis, structural details, and traditional design documents.

B. Object-Oriented Modeling

Parametric modeling does not inherently require object-oriented technologies, although in many instances it will. Sometimes referred to as “intelligent objects,” object-oriented designs use software objects that encapsulate information concerning each element within the software object rather than the database. Provided they conform to a common specification, objects can be created by third parties, as well as the model designer, and can appropriately interact within the model. The objects communicate with each other and with the model itself and adapt to information received from other objects. In effect, the model is a structure to support communication between “plug-in” objects that digitally simulate characteristics of individual building components that are arranged in a functional design.

Despite differences in architecture, both parametric and object oriented software share a functional, rather than graphic, approach to design, as is shown in the following example.

In a traditional CAD package, the designer draws lines to illustrate the location of walls, windows, doors, or similar structures. In effect, the computer is an efficient pencil. In a BIM design, however, the designer selects a pre-programmed wall object embedded with information about all of its relevant characteristics, not just its shape. If a window is needed, a window component is dropped onto a wall component that knows how to integrate the window into the wall and which can communicate with other components that may need to change (perhaps because of thermal differences) to accommodate the new window. Design by arranging components is sometimes referred to as designing with Legos because the design is built from a toolbox of existing elements.[7]

The difference between BIM and traditional design approaches is most striking when the design changes. For example, if a steel structure is designed with traditional CAD tools, the drafted design might contain columns and beams with specific connections. If a column is removed to create a larger bay, the designer must recalculate the size of adjacent columns, resize beams, reanalyze load paths, and re-detail the connections. In object-oriented design packages, such as Tekla Structures, if a column is removed, the model will communicate with the remaining columns, adjust their size as necessary, change beam dimensions, and change the beam/column connections. Tekla currently supports conduits to an object-oriented design package (ArchiCAD® by Graphisoft®) that can either initiate the design change or can adjust its model based on the changes in the ArchiCAD® model. Thus, a change in the architectural requirements can ripple through the structural design without direct engineering involvement. The model can “design” itself based on rules embedded in the objects themselves. Similarly, changes in Autodesk’s® Revit®, result in automatic adjustments within the model to maintain relationships between components. Not only is this process efficient, it sharply reduces unforeseen consequences.

C. Interoperability

The ability of different software packages to use, edit, augment, and exchange information depends upon universal standards for describing construction elements and systems. The National Institute of Standards and Technology estimates that $15.8 billion is wasted annually due to inadequate interoperability.[8] The International Alliance for Interoperability[9] (IAI) is dedicated to facilitating interoperability by defining Industry Foundation Classes as a uniform basis for collaborative information use and exchange. IAI currently has more than 400 members in 24 countries and is the leading interoperability organization.[10]

The National Institute of Building Science has undertaken the most extensive attempt to define standards for BIM. That National Building Information Modeling Standard was initially released for comment on March 13, 2007.[11] Its purpose is described as:

The NBIMS will provide the diverse capital facilities industry with a vision of how to support and facilitate communications throughout the facility lifecycle, from project inception through design and construction, even past demolition for improved operations, maintenance, facility management, and long-term sustainability.

The document was assembled by over thirty subject matter experts from across the capital facilities industry. It provides both a snapshot of where this burgeoning capability exists today as well as identifies work still needing to be accomplished. This first part of Version 1.0, which is now out for review, will be followed by Part 2 at the end of the year. Part 2 will contain items to be standardized across the industry using the NIBS congressionally authorized consensus process.

The NBIMS has six goals: 1) Seek industry wide agreement, 2) Develop an open and shared standard, 3) Facilitate discovery and requirements for sharing information throughout the facility lifecycle, 4) Develop and distribute knowledge that helps share information that is machine readable, 5) Define a minimum BIM, and 6) Provide for information assurance for BIM throughout the facility lifecycle. As an initiative under the buildingSMART® Alliance, it is garnering support form the widest spectrum of associations, agencies, organizations, vendors, and individual practitioners ever assembled.

Other solutions are being developed to facilitate interoperability. In addition to supporting IAI standards, Autodesk’s® Revit® BIM systems are available in discipline optimized versions that use a common engine that permit tight integration between the related models. Similarly, Gehry Technologies Digital Project software links to structural analysis packages.

D. 4D and 5D Simulation

Parametric models can be linked to scheduling information to add a temporal dimension (“4D”).[12] The scheduling information can be used to simulate construction sequencing and evaluate alternative approaches. The project can, in effect, be constructed in the computer before it is constructed in the field. In addition, the as-built schedule information can be used to show current construction status, and historic or posited information can be used to visualize the effect of delays in construction or other “what if” scenarios. Information concerning cost can also be linked to, or contained in the model (“5D”) allowing financial, as well as constructability, analysis. And given the power of relational databases, we can anticipate the integration of more data types as software developers push software and hardware capabilities.

III. Advantages of Building Information Modeling

A. Single Data Entry; Multiple Use

Traditional construction practices require the same information to be used multiple times by multiple organizations. Identical information is entered into different programs that provide specific solutions, such as structural analysis, code compliance, material quantities or cost estimates. Every repetition is an opportunity for inconsistency and error. Moreover, even if information is digitally translated from one program to another, translation can alter or corrupt the data. And versioning can be a nightmare, even with compatible programs. Drawing backgrounds are a recurring example of this problem. The architect’s consultants need to upload and maintain the basic design backgrounds they receive from the architect. These backgrounds, however, will change as the design develops and each party must take considerable care to ensure that they are working with the latest versions of the basic documents. The contractors and vendors must take the information provided by the designers, often in paper form, and enter it into their systems. As the design develops, changes in one party’s documents must be transferred back to the others. Errors begin to creep into the documents because updates are incompletely or incorrectly entered, and work can be wasted because parties are working from outdated information.

By consolidating information into a unified data source, the likelihood of data entry, translation, or versioning errors is greatly decreased.

B. Design Efficiency

Although the greatest efficiencies are obtained when BIM is used collaboratively, BIM design can aid a traditional design process. BIM software can reduce the cost of preparing 2D drawings in a conventional project, especially when designs are changing rapidly.[13] For example, in Revit®, any change in plan view automatically updates any section affected by the change. In Tekla Structures, changes in dimension or geometry automatically update details and related features. Moreover, using data rich elements instead of drawn objects, accelerates creation of contract drawings.

C. Consistent Design Bases

BIM modeling ensures that all parties working from the model share the same base. Under current practice, not all participants may be operating directly from the model. However, if the participants are using software that is compatible with the model, the base information can be moved, imported, or exported from the model. Moreover, periodic imports into 3D visualization software, such as NavisWorks’s Jetstream®, quickly exposes inconsistencies.

D. 3D Modeling and Conflict Resolution

The BIM model can render the design in three dimensions and does not require separate software to explore the model visually. The software allows specifying necessary clearances and can automatically detect physical conflicts (clash detection) between elements. Once detected, clashes can be resolved as the design moves forward. And because moving or changing an element is done inside an active model, adverse side effects are apparent and can be seen and evaluated. Thus, alternatives can be evaluated to determine the solution best benefiting the entire design. Besides design studies, the 3D model can be used for sequencing and constructability reviews. This process is significantly more efficient, flexible, and effective than traditional composite drawings or light table overlays.

E. Take-offs and Estimating

The model contains information, or can link to information, necessary to generate bills of materials, size and area estimates, productivity, materials cost, and related estimating information. It avoids the processing material take-offs manually thus reducing error and misunderstanding. Moreover, the linked cost information evolves in step with the design changes. The estimating advantages are so significant that some contractors will create models on 2D designed projects to use the model’s estimating capabilities.

F. Shop and Fabrication Drawing

In some instances, the models can provide construction details and fabrication information. This reduces costs by reducing the detailing effort and increases fabrication accuracy. In addition, because conflicts are resolved through the model, there is greater confidence that prefabricated material will fit when delivered. This allows more construction work to be performed offsite in optimal factory conditions. Subcontractors in the steel and MEP trades, regularly use models to fabricate their products.

G. Conflict Identification and Resolution

On complex projects, conflict identification and resolution is an extraordinarily expensive and difficult task. In many instances, designers do not have the time or budget to fully explore and resolve conflict issues. In other instances, full coordination cannot be accomplished during the design phase because the contractor will later design key systems, such as HVAC or life safety equipment that is not reflected in the design drawings. Even in a complete design-bid-build project, construction details and layouts may require information regarding the actual equipment that will be installed.

This information deficit is typically addressed by warning the contractor that the design is “diagrammatic” and that coordination will be required. Traditionally, the contractor coordinates physical drawings of different systems by overlaying them on light tables to determine if the various systems can actually be constructed in the allowed space. Alternatively, drawings for each discipline are merged and printed as color-coded composite drawings. Conflicts that are identified are brought to the designer’s attention through the request for information process, where solutions can be developed and clarifications issued. But light table resolution is inherently a two dimensional process applied to a three dimensional problem. It is notoriously difficult and fraught with error. For these reasons, conflicts are a primary source of contractor claims.

Building Information Modeling greatly reduces conflict issues by integrating all the key systems into the model. Design BIM systems can detect internal conflicts and model viewing systems, such as NavisWorks®, can detect and highlight conflicts between the models and other information imported into the viewer. The solution can then be checked to ensure that it resolves the problem and to determine if it creates other, unintended, consequences.[14] In a complex project, the savings derived from coordination can completely offset the model’s cost.

H. Visualization of Alternative Solutions and Options

Because it is inherently a 3D process, models are excellent methods for evaluating alternative approaches. Moreover, the ability to evaluate how changes affect key attributes, such as energy use, enhances the model’s usefulness as a thinking tool. However, the software interface can interfere with the creative process. In a study of one system, users noted that it was not “sketchy,” and therefore impeded the initial creative process.[15] This may lead to using freeform design tools initially with the results being loaded into the BIM system for refinement.[16]

I. Energy Optimization

Building Information Modeling systems, such as Autodesk’s® Revit®, can provide information for energy analysis. They can be used to evaluate lighting design and options, are in conjunction with their material take-off capabilities, and can generate documentation necessary for LEED™ certification.[17]

J. Constructability Reviews and 4D Simulations

Using the model, the contractor can visualize the entire structure, gaining a greater understanding of the challenges involved in its construction. By integrating 4D capabilities, the contractor can also simulate the construction process, which significantly increases the contractor’s ability to evaluate and optimize the construction sequence. The interaction between scheduling software and the model can also be used to evaluate the effect of construction delays and errors.

K. Reduced Fabrication Costs and Errors

The ability to use information in the model to directly create fabrication drawings avoids a problematic and difficult step in the construction process. In a traditional work flow, the fabricators must review the plans and specifications, prepare fabrication drawings, compare them to other fabrication and design drawings, have them reviewed by the design team, and eventually release the drawings for fabrication. Errors can occur at any stage. By using the data in the model, dimensional errors, conflicts, and integration errors can be avoided or significantly reduced. In addition, the model can be updated with as-built information allowing accurate fabrication of custom components, such as building facades.

L. Facilities Management

If the model is properly maintained during construction, it becomes a tool that can be used by the owner to manage and operate the structure or facility. Modifications and upgrades can be evaluated for cost effectiveness. Data contained in the model can be used for managing remodeling, additions and maintenance.

M. Functional Simulations

The 3D and conflict checking mechanisms can be used to simulate and evaluate emergency response and evacuation. For example, NavisWorks® was used at the Letterman Digital Arts Center to assure that fire response vehicles could navigate the parking structures.

IV. Barriers to Building Information Modeling

Despite BIM’s advantages, its adoption faces significant barriers.

A. Commercial Issues

Discussions of BIM generally focus on the technology. Although this is a fascinating subject, the key question is how BIM alters current commercial models. Rather than view BIM as a technology, it should be analyzed as a project delivery method, with new risks, rewards, and relationships. Unfortunately, new business models have not yet surfaced and early adopters are left attempting to integrate the new technologies into conventional practices.[18]

1. Immediate Benefits Do Not Accrue to the Key Adopter (Designer)

The benefits an owner accrues from BIM are easily seen. Using a flexible model allows design optimization, fewer construction errors, fewer design coordination issues and, thus, fewer claims. The owner can also use the model for management and operation of the facility. Contractors also benefit through less coordination and engineering effort and reduced fabrication costs. Quality is increased, cost decreased, and delivery times shortened.

For designers, however, BIM’s economic benefits are less apparent. Properly implemented, BIM design systems do increase efficiency by reducing duplicative and potentially inconsistent data entry. Multiple use of consistent data and the ability to quickly explore design alternatives also promotes efficiency and improved quality. But unless the designer shares in the economic benefits, the owner, not the designer, reaps the immediate benefits. Yet it is the designer, not the owner, who must adopt and invest in the new technology.

The asymmetrical rewards of BIM are a significant practical obstacle because design professionals are the linchpins of BIM. Design professionals must adopt the technology, install the software, train their employees, and champion BIM’s use. They need to restructure their workflows and reinvent the design process. If they do not share in the economic benefits, designers will have little incentive to adopt BIM processes. In fact, because BIM can increase the designer’s potential liability, there is a significant disincentive to adopting BIM. This concern is echoed in comments from the American Institute of Architects’ Technology Advisory Group, which stated in a recent monograph:

We fear there will be a tendency, driven by valid concerns about liability and insurability, to prevent such use of the architect’s design data. We believe this is the wrong answer and would jeopardize the future of architectural practice as we know it. If the architecture firm is not willing to deliver the potential value of the digital building model, the owner will seek delivery methods, probably contractor-led, that will deliver that value. The role of the architect will be diminished.

We believe, rather, that the architecture firms’ role and compensation should be enhanced by these technology developments. Obstacles to a free flow of data among the project participants should be overcome so that the architecture firm can deliver the full value of its work to the client and be rewarded commensurately.[19]

Although designers should logically benefit from BIM, new business models have developed slowly. The Australian alliance model is promising because it allocates risks and rewards among all parties. In the U.S., however, few projects are operating under new paradigms.

2. Absence of Standard BIM Contract Documents

Lack of standard contract documents also hinders development of BIM. Standard contract documents perform four key functions. First, they validate a business model by providing a recommended framework for practice. As noted above, a consensus business model for BIM has not emerged. Second, standard documents establish a consensus allocation of risks and an integrated relationship between the risks assumed, compensation, dispute resolution, and insurance. Custom agreements, unless crafted by seasoned practitioners, are often unbalanced and overlook key issues Third, standard documents reduce the effort involved in documenting the roles and responsibilities on a project. Designers want to design structures, not structure contracts. Finally, crafting custom documents increases the transaction costs, and thus reduces the profitability of every transaction. Unfortunately, the current standard contract documents provide little guidance to the BIM practitioner.

For example, regarding electronic information transfer, the AIA contract language consists of the following:

1.3.2.4 Prior to the Architect providing to the Owner any Instruments of Service in electronic form or the Owner providing to the Architect any electronic data for incorporation into the Instruments of Service, the Owner and the Architect shall by separate written agreement set forth the specific conditions governing the format of such Instruments of Service or electronic data, including any special limitations or licenses not otherwise provided in this Agreement.[20]

After many years, the AIA introduced the “separate written agreements” envisioned by the 1997 documents, the Digital Data Licensing Agreement[21] and the Digital Data Protocol Exhibit.[22] Although these are helpful additions to the existing document sets, they do not attempt to address BIM’s implications. And AIA Document A201-1997, General Conditions of the Contract for Construction, does not discuss electronic documents, except