Quantity takeoff in estimating is a necessary part of the effort to get projects from a design idea to a tangible structure. Construction companies have been doing a variation of quantity takeoffs for decades. As the construction industry has embraced technology to improve and realize efficiencies the quantity takeoff aspect of preconstruction is starting to follow suit. From visually counting items in drawings to performing 2D takeoff with specialized software and getting those numbers into an estimate has been the status quo for several years. The next enhancement for quantity takeoff is 3D.
Being able to use 3D models for quantity takeoff has several benefits.
Expedites the takeoff process.
While 2D takeoff has been able to get the job done it does not allow for a visual inspection. Estimators are able to filter down by systems in 3D models and have the 30,000-foot view of the project as well as zoom in to the one-inch view. Very senior estimators can look at a 2D drawing and visualize what is needed to construct the project as well as what may not be drawn but should be included in the estimate. Using 3D models to do quantity takeoff allows estimators to quickly see what has been designed, which elements are missing that should be included in the estimate, and grab several pieces of data in one visual swoop to keep moving the estimate forward.
Quickly seeing what changed in the 3D model during the quantity takeoff process saves time as the project continues to move forward through the design and construction phases. Estimators can use version tracking in 3D quantity takeoff to compare changes to the project as they arise.
There is a holistic aspect of 3D quantity takeoff. It boils down to the simplest part of the project: the project number. This number houses all of the details related to a project; timesheets, file document structure, invoicing, production tracking, etc. Breaking down the 3D model by phases, disciplines, levels, and/or sub-contractors will drive a lot of the data that is needed in the project number. The data housed within that specific project number helps mitigate risks, improves efficiencies, and builds historical data to be used on the next project.
The benefits of 3D model quantity takeoff are substantial and real. However, Beck Technology often hears “How can I trust the model I’m getting?!” We talked to some of our customers who are leading the industry with 3D quantity takeoff and they gave us their quality control process. Their recommendations below are the steps to incorporate 3D models from architects and structural engineers.
BIM execution plan.
A BIM execution plan works well in a design-build project delivery format when the contractor is brought into the construction project at the beginning. This plan is an agreement between the designer(s) and the contractor for how the model will be built and dissected.
Interrogate the model.
When a BIM execution plan is not a viable option then start with this step. Either way the contractor must interrogate the model. Some construction companies have an internal group that can review those 3D models and decipher how the model was built, what is missing, and what systems were grouped together. They can decipher the family tree used in the model and what to look out for. This information is then passed along to the estimator.
If you don’t have this resource at your company then a visual inspection is required. By doing a quick tour of the model and asking yourself “Why is it modeled this way?” may bring up some items that are missing from the model but should be included in the estimate. Additionally, visually seeing how items were modeled will give you a good understanding of whether it was designed with the construction in mind. For example, a floating wall doesn’t happen in real life but they do in models and that room system may have been duplicated throughout the model.
Build a strategy for using the model.
Have a list of key things that are in the model, items that are modeled correctly, and if something is not in the model then come up with a collaborative plan on how to get it in there.
- If you are dipping your toes into the 3D modeling quantity takeoff feature of DESTINI Estimator our customers recommend starting with structural steel. Most structural engineering firms tend to have a similar modeling framework which is helpful to get some lessons learned under your belt.
- Create a grouping within DESTINI Estimator for each of the architects the construction company works with. This allows estimators to interpret what the architect has put into the model fits within MasterFormat. Since architects use different databases to build their models this allows DESTINI Estimator users to quickly breakdown the 3D model quantity takeoff into the necessary format for estimating.
Do a gut check.
Grab a couple of rooms and compare them within 2D quantity takeoff to ensure your 3D takeoff comes up with the same numbers. For example, once you have finished taking off the concrete in one room in 3D takeoff then you can do the same room in 2D takeoff. This helps verify that the model data is correct as you continue to move forward.