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3 Ways Building Information Modeling (BIM) is
Changing Estimating

Let’s begin with a fact that is undeniable: virtually every new capital asset that is being constructed today was designed in digital 3D. Not surprising, right? Over the past few decades, the engineering and design industry has evolved from paper (2D), to digital 2D, to digital 3D. That evolution was certainly driven by advancements in design software (and the horsepower of the computers that run those programs), but also reflects another undeniable fact: owners love 3D. Even in today’s technology-driven world, it is not unusual for owners to commission a scale model of a new asset to be built. These physical models are often intricately crafted from balsa wood and artfully detailed and painted, or better yet, 3D printed to show the world what this fabulous new asset is going to look like. The purpose of this physical representation is not only to compel investors to support the project, but it also makes the asset “real,” creating context and an emotional connection you simply can’t get from a 2D rendering.

The problem with scale models is that they are permanently stuck in a single point in time. And with frequent design changes that occur before an asset breaks ground, digital 3D as a design medium is now the closest thing we have to the real thing. Digital 3D provides a world of possibilities to “interact” with the asset from every direction and every angle, but also easily iterate through new ideas and “what if?” scenarios. Want to make the parking garage one story taller? With a digital 3D model, in just minutes, maybe even seconds, you can see what that looks like and how it affects the view from the office tower. 

So now with the evolution of building information modeling (BIM) and 3D as the standard for design, it is worth asking what impact that’s having on estimating; the next major step in an asset’s journey through the construction life cycle. Depending on whom you ask, you will either hear that 3D design is having a monumental impact on estimating, or it is having no impact at all on estimating but “any day now it will be monumental.” 

That disparity depends not only on what sector of the industry you’re in, but also on the contracting philosophy of individual owners and the designers they hire. The most innovative owners are mandating a model-driven approach to managing assets throughout the life cycle, from design through construction and into operations. For such owners, a 3D “digital twin” that connects design, construction and operations creates tremendous benefits for stakeholders at every stage.

Of those stages, construction cost estimating has been identified as a leading beneficiary from the use of BIM. But in order for models to positively impact cost estimating, the first step is to make such models accessible to estimators. Amazingly, it is not uncommon for a construction team to receive only 2D drawings from which to perform their quantity takeoff for estimating purposes. That’s right. Even though the project was designed in 3D, but we’re going to create 2D drawings from the 3D model and give those to estimators to manually figure out all the dimensions and counts that are already sitting right there in the 3D model. Though there are (sometimes valid) legal issues that can get in the way of sharing the models, they are gradually fading to a point where more and more projects are making current and accurate 3D models readily available to the construction team.

As a result, 3D models are becoming more valuable as a digital source of information for estimating. This is especially true as the building information modeling movement in recent years has expanded the types of information that can be found in a typical model. In addition to all the information needed to render the model in three dimensions, it is not uncommon now for models to contain spec information and other metadata for every object, or element, in the model. This information is invaluable to estimators; it provides useful context, and creates a means to filter, group and otherwise manage the data in the model. For example, an estimator might want to group all the elements in the model by material type, to get a total count of pipe fittings that are made of carbon steel, or filter the model down to just the mechanical elements while hiding the architectural elements for better visibility to the piping systems inside the building. 

Ultimately, the ever-increasing availability of 3D models, coupled with the expanding universe of information contained within them, is impacting the construction estimating process in three key ways. First and foremost, models provide the opportunity to transform the task of quantity takeoff from a highly manual process to an all-digital process. With the right tools, estimators can get the quantity information on which to base their cost estimates directly from the 3D model. Currently the most common approach to quantity takeoff is to open a 2D drawing, such as a PDF or JPEG file, on the screen and manually trace over every line in the drawing to calculate square feet of drywall, linear feet of a piping system or cubic yards of a concrete foundation. This is a tedious and time-consuming process, and one that is ripe for error. 

By using a model-based approach, an estimator can “interrogate” the model using queries and expressions to arrive at those quantities, often in far less time, and always with a much better ability to deal with changes when the design invariably gets revised. By simply loading a revised version of the model, estimators can automatically see the impact of design changes on their takeoff quantities, with far less effort than re-tracing over the 2D drawings.

This leads to the second major impact that BIM is having on estimating; building information modeling is changing the skillset of the estimator. The ability to perform manual takeoffs on drawings is still important, but that skill is starting to give way to data management skills. Getting the information out of a 3D model — and transforming it into useful quantities for estimating — is a process that requires some entirely new skills compared to those required to do takeoffs on drawings. Estimators eager to embrace this new world have self-learned these data transformation skills out of necessity, adding to their repertoire talents you might otherwise see on the resume of a computer programmer or database administrator. Fortunately, software vendors are starting to provide purpose-built solutions that simplify the process of connecting models with estimates. Nonetheless, expectations of those in the estimating profession to have data management and data transformation skills, along with familiarity analyzing 3D models, will continue to rise.

The third and final area in which building information modeling is changing the game of construction cost estimating is by providing estimators with the traceability needed to confidently stand by their numbers. Anyone who has ever sat through a bid review is accustomed to the question, “where’d you get that number?” which is usually asked in a tone that implies something more like, “Do you even have a clue where that number came from?” When estimates are connected to models, however, estimators now have the ability to trace quantity values back to the original source. The traceability of a model-based estimate helps validate that estimate quantities are correct and current, instilling confidence in the numbers. 

In essence, a model-connected estimate is the most intimate a construction cost estimate has ever been with the absolute source of its quantities. Today, contractors trace over 2D drawings to calculate quantities, and those quantities are then entered into estimating software. That process can go on for weeks, with new drawings being issued along the way, and the process reoccurring numerous times. By the time the estimate is ready for sign off, it is understandable to question if the estimate has everything included, and whether the quantities are accurate and current. With a model-connected estimate, there is a direct line between the quantity in the estimate and the absolute source of that quantity. In the world of model-based estimating, estimators will be able to confidently answer the question, “Where’d you get that number?” simply by clicking on a quantity in the estimate and instantly displaying the elements inside the 3D model contributing to that quantity; “That’s where I got that number.”

The craft of construction estimating is all about inspiring confidence — confidence in the numbers on which everyone’s hopes and dreams for the project are riding. Evolving to a world of model-connected estimating, where manual 2D skills migrate to 3D data intelligence, can have a profound impact on cost estimation, and result in a whole new level of confidence in numbers that will likely make or break future projects.  

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