Don’t Forget to Look Down – A Case for Floor Flatness

by Chris Pechacek, McCarthy Virtual Design and Construction Director

Constructing a state-of-the-art facility demands the highest quality standards. An experienced builder must understand the unique complexities of each specific project to ensure success. However, beyond the obvious are those potentially overlooked quality considerations that must not be forgotten. A key case in point is floor flatness.

Imperfections in floor flatness can have significant impacts on operational efficiencies. Even the smallest variation can interfere with equipment accuracy, usage of space, or comfort of the facility to users. To deliver a superior level of floor flatness, your builder must put in place a detailed plan and implementation strategy.

For example, an innovative Structural Survey and Floor Flatness Program is currently being implemented at the new 1 million-square-foot flagship Kaiser Permanente Phase 2 project in Oakland, Calif. To achieve McCarthy’s internal Floor Monitoring Program requirements, the team leveraged extensive Virtual Design and Construction processes to meet the deliverable requirements. The approach outlined below offers a glimpse into possible steps your builder might take to meet your project’s floor flatness requirements.

The effort for Kaiser Permanente centered around completing structural surveys of the steel and metal deck prior to placement of the concrete deck fill and then again post-placement for measurement of displacement and its effect on floor flatness and floor levelness. This required “surveying” each beam — ends and mid-span — as well as the deck bottom center of bay, utilizing new control and layout services coupled with 3D Laser Scanning and cutting-edge software for post-processing the data.

Determining Survey Variances
The first step in the process was to lock down the project control to a very tight tolerance and then transfer the control points onto each floor for use in registering the follow-on laser scanning point clouds. To kick off the effort, the team met to determine the requirements necessary to achieve site and floor control to within 1/16”.

Use of 3-D Laser Scanning
Once local control was established, the team was able to utilize 3-D laser scanning to quickly capture the steel as-built conditions prior to and post concrete placement. After completing registration of the point clouds in the scanner’s native software for each floor, the concrete and steel fabrication models were combined to validate work in place. From there, surfaces were modeled from the laser scans. The surfaces elevations were transferred to AutoCAD to measure the displacements of each point and finally produced the structural survey plans. To validate the accuracy of these results, the team also took a sample using the traditional methodology. These results confirmed final accuracy fell within pre-determined variances. 

Performing Beam Deflection Analysis
Using the structural models and measured displacement points, plans were then produced for beam deflection analysis. The output of this process was then submitted to the owner and the structural engineer of record for review and acceptance. This mitigated risks that might occur downstream by validating that there no issues up front and identifying any issues that could be proactively addressed.  

Inspection Results and Next Steps
Kaiser Permanente’s special inspectors performed traditional floor flatness and floor levelness tests, reporting the project exceeded both project requirements.

Once each deck had cured, however, the team then took the additional step of scanning the concrete surface to capture all the area elevation variations and generated topographical plans with elevation separations of 0.01’ for purposes of seeing what the floor was actually doing. 

Next, the topographical plans were brought into AutoCAD and the architectural backgrounds were overlaid onto the topographical plans, offering a complete picture. This revealed areas that needed to be addressed such as areas that were high or low, or where transitions may need additional focus due to program space layout. This also helped ensure that key, critical locations such as operating rooms were of the highest quality.

Conclusion
While technology tools continue to evolve, developing a Structural Survey and Floor Flatness Program can play a significant role in ensuring the quality of your facility is top-notch. On the Kaiser Permanente Oakland Medical Center project, this innovative process resulted in reducing the schedule time and costs as compared to traditional methods and provided a higher quality facility for owner use. Bottom line, this effort helps mitigate all team member risks, reduces costs and schedule, provides higher quality, and ensures owner expectations are exceeded.

About the Author
Chris Pechacek is the Virtual Design and Construction Director for the Northern Pacific Division of McCarthy Building Companies, Inc. His 19 years of construction project management experience includes mega healthcare projects, correctional, multi-building campuses, data centers, and large public works projects. Chris graduated from Brown University with a bachelor of science in Civil Engineering and proudly served his country as an Infantry Captain in the United States Army. Chris serves on many BIM Advisory committees including California Department of Corrections and Rehabilitation, national CSI committees, Tech Com, OmniClass, PRM, BOKA and Corps of Engineers. He has also shares his experience and knowledge by guest lecturing at area universities and at many local, regional and national events.