My recent participation in a workshop at the AEC Implementation Summit, a highly recommended annual event hosted by the Construction Progress Coalition (CPC), brought into sharp focus a persistent challenge: BIM-based cost estimation. This is a topic of immense importance, holding the promise of significant industry value through improved decision-making, early cost control, and real-time updates to cost estimates as projects evolve. Not being frequently involved in construction cost estimating myself, I might have assumed this was already common practice. However, the very necessity of a workshop to promote BIM’s use in cost estimating, coupled with insights from those actively involved, clearly indicates otherwise. Our small group breakout specifically explored how BIM could generate quantities accurate enough for estimators to trust. (For more details on the event and its outcomes, connect with the CPC.)
Reflecting on the summit, I continued to muse over the topic of BIM+Cost. I found myself somewhat surprised that the industry at large—though not necessarily individual organizations—still grapples with BIM’s fifth dimension (5D), which is generally accepted as the integration of cost into a 3D model. Despite 5D having been conceived and referenced countless times over many years, anecdotal reports from the field consistently indicate that cost estimators largely lack trust in BIM and the output.
While some practitioners assert that their companies have successfully completed proof-of-concepts for accurate BIM-based quantity takeoffs (QTO) and implemented BIM-based cost estimating processes, and have even piloted parallel workflows to validate BIM-extracted material quantities against traditional estimation methods, a critical gap remains. When I inquire if these successes have been documented and shared with other construction groups, the responses are invariably “no,” “not yet,” or “it’s tied to our company’s internal process.” This often leads to frustrating encounters with individuals who claim to have “solved it” but remain unable to provide tangible details. Show me the money… (related data)!
The Search for Industry Standards
This leads to a crucial question: Where are the industry standards for BIM-based cost estimation? While numerous resources exist, they are often scattered. BIMForum’s Level of Development (LOD) specification, for instance, provides a robust framework for defining the modeling fidelity of individual elements and their intended reliability. It’s crucial to note, however, that BIMForum explicitly states LODs apply only to elements, not the entire model. This fundamental distinction means any given model will invariably contain elements at varying LODs. Documenting LOD for all model elements can be time-intensive for design teams, and interpreting these varying levels for BIM-based cost estimation can be perplexing.
Similarly, Penn State’s BIM Execution Planning documents, which later contributed to the National BIM Standard, outline 5D cost estimation as a BIM Use and reference various classification systems. Yet, these documents stop short of providing detailed implementation guidance. While the USACE Minimum Modeling Matrix has made strides in standardizing expected LODs for model elements—offering a baseline for consistency—its widespread adoption for cost estimation purposes remains limited and is currently being evaluated for applications to horizontal construction, signaling the ongoing need for updates. Ultimately, while standards are available, the critical void remains in detailed, practical implementation guidance.
It’s also worth distinguishing Quantity Takeoff (QTO) from Cost Estimation. Though QTO is a fundamental component of cost estimating, the terms are often conflated within the industry, despite being distinct. While some how-to guidance exists for performing QTO using specific software, this specificity for QTO alone underscores that the overarching problem isn’t a lack of standards, but rather a scarcity of practical implementation guidance for the broader cost estimation process.
Why the Distrust? Three Core Factors
So, why do cost estimators distrust the models? I propose three fundamental sets of factors: Model Data, User Adoption, and Process Reengineering. Yes, I am purposefully avoiding the overused tripartite of “people, process, and technology”, but you may draw the connection if you like/must.
Model Data
Inconsistent model quality is a pervasive issue, whether across the industry, within an organization, a project team, a federated model, or even a single model. Many models are riddled with “junk”—erroneous information, superfluous data, or forgotten temporary placeholders. Organizations and agencies often fail to adequately quality-check models before distribution or use, leading to the discovery of discrepancies downstream and an erosion of trust in the data.
Models frequently contain unverified default values, missing classifications, incorrectly modeled components, or elements that fail to meet documented LOD requirements. All too often, robust QA/QC practices for models are deprioritized in favor of meeting immediate deadlines (e.g., submitting 2D construction documents during design). Such frequent variations transform reliance on the model for cost estimation into a significant gamble.
Furthermore, not every cost consideration has a direct model element equivalent, and costs can fluctuate significantly based on material, object type, location, or labor demands (e.g., placing concrete on an upper floor typically costs more than on the ground). It’s also worth considering that estimators may not always require the level of detail we assume; they might quickly determine material cost from a linear footage application, rather than needing a fully modeled and automatically extracted element, so in some cases, over-modeling becomes a deterrent to use.
User Adoption
This encompasses numerous subcomponents, including acceptance of change, training, knowledge, ability, and capacity. Key questions arise: Are estimators adequately trained on what they can confidently rely upon from BIM? Do the complexities of model data and LOD inherently hinder adoption? How do estimators discern, from project to project, which components offer reliable information and which do not? Do even BIM managers possess this clarity?
Moreover, are estimators actively included in technology education and training efforts? Often, cost estimating personnel and activities operate in silos, separated from BIM managers, coordinators, and modelers. This frequently results in a significant knowledge and training void regarding LOD and 5D from a cost estimator’s perspective. Beyond knowledge and skills, successful user adoption is influenced by factors like ease of use, organizational mandates vs. voluntary adoption, and the prevailing change implementation culture in an organization.
Process Reengineering
A critical need arises when practitioners are expected to transition from trusted traditional approaches to new, technology-infused methods. Can we realistically expect seasoned estimators, comfortable with established processes, to eagerly embrace new technology without a meticulously planned new process? Where can they find documented, industry-accepted best practices for BIM-based cost estimating?
The industry’s requirement extends beyond mere standards; it demands practical implementation guidance and best practices. This includes identifying typical modeling practices that render certain elements more reliable for QTO (e.g., concrete versus gypsum board). While BIM managers and coordinators possess the technical expertise to extract quantities and potentially even the resources for model quality checks, many in these roles lack direct estimating experience.
A recurring pitfall in process reengineering efforts (or workshops) is the failure to involve key stakeholders upon whom the solution hinges. For instance, a cybersecurity requirements workshop without cybersecurity policy writers, or a committee on “Model as a Legal Document” lacking legal or insurance representation. Similarly, reengineering BIM for cost estimating processes without the integral involvement of full-time cost estimators is a fundamental oversight. This echoes a core principle of the Last Planner System (LPS): individuals and teams closest to the work must be integral to its planning. Therefore, a foundational step in reengineering cost estimating processes with BIM models is a comprehensive understanding of what the cost estimator truly needs.
Conclusion
In summary, the widespread implementation of BIM in cost estimating hinges on addressing three critical areas: Model Data, User Adoption, and Process Reengineering.
- Model Data: Models must contain reliable data, validated to an agreed-upon and understood level of fidelity.
- User Adoption: The primary users—cost estimators—require comprehensive support, including education, training, and leadership, to effectively embrace technological change.
- Process Reengineering: The existing process must be reengineered, supported by robust documentation, best practices, and clear implementation guidance.
While no single individual or organization can unilaterally create industry-wide consensus-based best practices, progress begins with ensuring appropriate model data quality, empowering cost estimators with the necessary support to adopt new technologies, and reengineering processes to align with both technological capabilities and user needs. Concurrently, it is imperative to actively engage with industry associations. Voice the importance of this topic and seek out groups driving meaningful progress in this domain, and most importantly, get involved.