Reaching Target Project Costs with 5D BIM Estimating

Reaching project target costs is a whole lot easier with 5D model-based cost estimating. 5D model-based cost estimating links and maps model elements and associated construction quantities to develop a project cost plan. 4D construction sequencing brings the element of time or schedule to the 3D BIM model; 5D brings the element of cost. This cost estimating method is an effective way to work together with the owner and project stakeholders, leveraging a wealth of information and experience from the model to the project in a visually communicative way. Use of 5D model-based cost estimating may still be a fairly new practice for some people. However, I am pleased to report that we’ve had great success using model-based estimating over the past 10 years. This article aims to illustrate how 5D model-based cost estimating can be successfully applied on your next project.

Concurrent Scheduling and Cost Estimation

5D model-based cost estimation occurs concurrently with VDC during the preconstruction 4D construction schedule sequencing phase. The 4D model-based project schedule integrates a series of multi-disciplinary performance models, which includes the building or structure, manpower, workflow sequences and processes, and overall organization of the design and construction.  This effort requires continuous referencing and analyzing the project model to determine material quantities, schedule milestones, project cost, material quantities as well as identification of potential project risks.  All of these variables are carefully considered throughout Building Information Modeling (BIM).

Cost Estimating and Cost Monitoring in Real Time

Model quantities and dimensional information are directly linked and mapped to the estimating database. Cost database integration allows you to provide real-time cost plans. While this may sound really simple, it must be said the model needs to be properly developed in order to be useful in deriving quantities. Modeling content and level of accuracy needs to be discussed between parties (model author/5D users) prior to modeling. It is essential to communicate early on with the design team about relevant design intelligence that  be used to accelerate the estimating process which will allow for an accurate cost estimate. 5D model-based estimating also leverages estimating department expertise , in effect a knowledge base of cost and time variables the BIM model can draw upon. 

Accurate cost estimation coupled with a clear representation of accrued cost across each project phase allows for a significant and positive impact on construction management. In addition, 5D BIM provides intuitive feedback on cost saving strategies (value engineering and constructability review) and cost predictability.

Responding to design cost option studies, design changes and value engineering requested by owner, and architect is commonplace. Timing is of the essence in the decision-making process; it is important to prioritize the response to these requests. 5D model-based estimating allows you to immediately performing estimate updates without delaying the decision-making process. In my experience, it’s quicker to visualize, discuss, and approve a change on-the-fly using the model than receiving sketches from the architect via email and hoping to get back with an instant answer.