Critical Best-Fit Analysis for Construction Managers

| August 1, 2017

by Michael Feldman

When an addition, renovation, or adaptive re-use project enters the construction phase, it seems that responsibility is falling on the construction managers (CM) more and more to verify in field (VIF) the existing conditions. Revit models are delivered to the CM with all of the design elements, including all structural and architectural features; however, it is hard to know the origination of these models. Were they built by compiling record plans? Actual field measurements by surveyors? Survey-grade 3D laser scanning performed in a way to accurately stack all floors and columns to one-quarter-inch accuracy?

We are routinely called to work with the CM to perform quality control on these models so they can know what can be relied upon during the critical phase of construction. Sometimes it is necessary to perform a 3D scan of the building and utilize the proper procedures to achieve an accurate point cloud model. After this, we can deliver it to the CM, or we can run this data in Navisworks along with the existing model to see if there are any inconsistencies. We have been performing this service for the past 10 years, and we believe we have been able to help CMs mitigate risk when they are delivered plans and information that are labeled VIF.

We also perform a similar service when we are asked to establish a reference grid for an existing structure. We accurately locate columns and structural elements of the building to establish its as-built condition. A best-fit overlay is achieved by analyzing the displacement between the design and as-built. The results are then represented on a worksheet where the as-built condition is shown relative to the reference column line grid. The grid can now be accurately laid out and used by all team members to achieve consistent results.

This service has been an integral part in helping simplifying the complex for our clients. It is problematic when our clients begin construction with a hypothetical grid for an existing building without having a true relationship between the two. This has caused a good amount of construction delays and redesigns in the past, and we are happy to say that when we perform our best-fit analysis for clients, it keeps their projects running on time and on budget. This is just one way you can count on our firm to get it “Right. From the Ground Up.”

Feldman is providing construction engineering services on four of the five largest construction projects in the Boston area. Wynn Resort in Everett, Four Seasons in Back Bay, Millenium Tower in Downtown Crossing, and Boston Children’s Hospital are all projects that require our full suite of construction and BIM-related services.

Michael Feldman


Michael Feldman is president and CEO of Feldman Land Surveyors.



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