5D BIM, or 5D Model Based Estimating, links a 3D building model schedule and cost data to allow for improved cost estimation. While 3D modeling provides benefits during design, 5D BIM provides additional advantages to estimators by enabling faster and more accurate takeoffs directly from the model. However, challenges remain as models may not include all necessary takeoff information or specifications. Leading technology companies are working to develop solutions that integrate 2D and 3D content within estimation tools and link model objects to specifications to help estimators overcome these challenges.

1. The fifth dimension
5D BIM defined and refined
While Building Information Modeling (BIM) applications are not new, they are now moving
beyond 3D modeling all the way to 5D modeling, often called 5D Model Based Estimating. It’s
easy to see how 3D building modeling is beneficial during a building’s design phase, but
increasingly, BIM is being adopted by contractors for use during the estimating phase. It’s an
evolving process to be sure, and there are challenges to be met in order to usher it into wider
adoption. But the benefits to estimators are real, and major players in the BIM arena are
bringing resources to overcome the challenges. Let’s explore what 5D BIM is, what it promises,
and what the industry is doing to deliver on those promises.
5D BIM defined
When you link a 3D building model with the construction schedule, we call it 4D BIM. When
you link and map the model to an estimating database to calculate costs of items and
assemblies, you have entered the fifth dimension – 5D BIM.
Multi-dimensional benefits
While the advantages of 3D modeling during a project’s design phase are obvious, this
dimensional approach is also capable of providing clear advantages to estimators, including:
Improved visualization
3-D building information models give estimators a realistic visual and information-rich
representation of a project from which to check quantities and validate costs. The model also
helps estimators better understand the complexity of a project and more readily identify areas
of potential risk.
Faster and more accurate takeoffs
5D BIM can speed up the estimating process. By using BIM tools integrated with estimating
software instead of drawings, the takeoffs, counts, and measurements can be generated
directly from the underlying model. Typically, 50-80% of the time needed to create a cost
estimate is spent just on quantification. When you do not require manual takeoffs, you can
save time, cost, and greatly reduce the potential for human error.
Greater collaboration
The BIM process, enhanced by desktop, mobile, and cloud-enhanced tools, fosters greater
collaboration between the entire building team. By connecting to BIM tools, estimators can
provide reliable cost feedback to the design team and the customer early in the process, while
changes and design tweaks are simpler – and less costly.
Deconstructing the challenges
Despite the benefits, 5D BIM has some challenges to overcome before it wins the hearts (and
replaces the pencils) of estimators. Two of those challenges surround take-off and
specifications.

2. Missing take-off information
A BIM project model doesn’t include all the information estimators need. A 3D model, for
instance, may contain a pipe schematic with lengths, but estimators still need to refer to 2D
drawings to take off the hangers. Or floor coverings may not exist in the model, but can be
found on the 2D drawings. As a result, estimators may have to use multiple, unconnected 2D
and 3D takeoff systems, complicating the process and increasing the chances of error.
Some 2D takeoff tools are available inside 3D BIM software. However, it’s generally
acknowledged that these tools currently don’t provide the same level of capabilities estimators
require for 2D production estimating work. Plus, the majority of takeoff software is still 2D.
Consequently, estimators are looking for ways to work concurrently with both 2D and 3D
content during the takeoff process.
Scarcity of specs
Another estimating concern with 3D models is the lack of specifications. From a design
perspective, there may be little value to putting specs into the model. In fact, it may not be
possible to build a model containing all the job specifications without impacting model size and
performance. Architects and designers may attempt to resolve this issue by creating links in the
model to external specification documents. However, these links, which must be maintained by
different stakeholders, can easily break as specifications change throughout the project leaving
the estimator without easy access to vital information.
5D BIM refined
Basically, the estimator has a very different view of a project from the person who designed it.
So the juncture where those two disciplines meet needs to be contractor friendly and practical
for the estimator. To achieve this, leading technology players in the building information
modeling, takeoff, and estimating software arenas are working together to offer solutions
that will bridge the current gap between BIM and estimating.
The new solutions will offer takeoff tools that make it possible for estimators to do production
estimating work concurrently with both 2D and 3D content. This will streamline the now
fragmented takeoff process and eliminate additional error-prone work. The ability to link
construction objects in a model to assemblies in a customized estimating database will also be
available, providing the estimator with the specification variables that are often missing in
models.
BIM technology is advancing rapidly, and estimators stand to be the next beneficiaries. Stay
tuned for more on the fifth dimension.