During the last 20 years, quantity takeoff tools have evolved from paper plans and roller balls to digitizer tablets, and then to electronic 2-D plan takeoffs with PDFs, and finally to today’s current method of 3-D quantity takeoffs from BIM.
While quantity takeoff inputs have evolved significantly, the need for highly flexible, adaptable cost estimating software that dramatically reduces time spent performing quantity takeoffs has remained relatively constant. Estimators often complain that they didn’t get a degree in construction management so they could dedicate half their life to counting doors, windows and columns. More recently, the evolution of 2-D quantity takeoff tools has given estimators more time to explore value engineering options for greater accuracy and an improved project deliverable. By providing a highly visual audit trail, these tools have allowed estimators to maintain their confidence in the itemized quantities.
3-D BIM models have introduced another dramatic step forward in reducing the time associated with performing quantity takeoffs. For example, the ability to query a 3-D model and instantly see the total surface area of interior walls on the first floor of a large facility, without the need to digitize every wall, can boost productivity by 80 percent to 90 percent.
Early Attempts at 3-D Quantity Takeoff Solutions Fall Short
As CAD authoring solutions began providing 3-D object-oriented design tools, many of them proclaimed to offer quantity takeoff and estimating solutions as a byproduct of the model. Contractors that evaluated these tools quickly discovered the quantities generated from the models were too design centric and not construction focused. In addition, contractors quickly discovered that these tools fell short of providing a viable estimating solution. At best, they produced a simple bill of materials, with construction systems absent from the model and limited support for the labor cost and production rates necessary to complete an estimate.
Some of these early solutions failed due to poor capability; namely, a feature set that demonstrated a lack of understanding of the estimating discipline. The developers of these tools didn’t understand that an estimator accomplishes several essential tasks when performing a takeoff. More than performing a quantity takeoff, estimators must construct the project in their head, and become familiar enough with it to put their signature on the accuracy of their estimate.
Today’s Estimating and Quantity Takeoff Challenges
Project portfolios, especially for large construction firms, are incredibly diverse. General contractors have an increasing number of model-based projects, with the majority of projects still based on 2-D plans. In fact, even for projects that include a 3-D BIM model, construction components are often missing from the model, resulting in the need to perform a hybrid of both 3-D and 2-D quantity takeoffs.
Multiple inputs require separate tools for a 2-D takeoff versus a 3-D takeoff. These tools often act independently of the estimating software that will ultimately need to consume those quantities. In addition, separate takeoff tools require the estimator to learn multiple systems, each with their unique user interface workflows.
Compounding the issue, these tools often depend on a cost library specific to the takeoff tool. One can see the complexity and redundancy: a cost library for the 2-D takeoff solution, a cost library for the 3-D takeoff solution, and in most cases an entirely separate cost library for the actual estimating software. In other words, every time there is a material price update, someone has to update that price in as many as three separate cost libraries.
Identifying Quantity Variances from One Version of the Model to the Next
Today, model-based design tools are so powerful that they encourage design alternatives to be implemented throughout the pre-construction phase. As the model becomes more inclusive of all construction systems, the ability to identify the design changes from one iteration of the model to the next becomes increasingly complex.
In the end, it’s not enough to perform a single takeoff with the initial design. Instead, an estimator is constantly looking for ways to highlight or isolate design changes from one version of the design to the next. In most cases, an estimator has to use one software solution to locate the design changes in the model, and a separate software solution to locate the change on the next set of 2-D plans.
Accurate, timely and transparent cost estimating is critical to the success of any construction project. However construction estimating is a complex process that often relies on disparate inputs in both 2-D and 3-D, multiple cost libraries, and a range of point tools for estimating and takeoff. That kind of complexity can stand in the way of success.
Thankfully, technology advancements are coming to market that eliminate this unnecessary complexity. The most robust tools combine best-of-breed estimating and takeoff solutions to help estimators increase efficiencies, win more work and maximize the profitability of projects. The availability of purpose-built, sophisticated estimating platforms that integrate cost analysis for both 3-D models and 2-D drawings and that are tied to a single cost library have become instrumental in helping general contractors and construction managers increase efficiencies, win more work, and maximize the profitability of projects before, during and after construction.