Advantages to the mason contractor creating its own models of any and all masonry on a project are many. Potentially, it improves communication and ensures all parties of the design and construction team are on the same page as far as constructability and other expectations. It also can improve ordering accuracy, productivity and budget internally. In the case of 7Seventy7, building information models of the masonry did all of the above.
Milwaukee’s new high-end, high-rise apartment building boasts city views and topnotch amenities with 314 units situated atop a 1400-space parking garage.
Masonry used at the pedestrian level and parking stories features 5000 burnished CMU on the ground-level exterior and entrances to the parking structure Figure 1 along with 720 lineal feet of granite panels at the building’s base. The eight-story parking garage utilizes about 72,000 concrete masonry units (CMU) in the lower levels.
Once KMI Construction’s Fred Kinateder Sr began working with the BIM for Masonry initiative developing standards and technical guidelines for the implementation of BIM technologies to support the design and construction of masonry buildings, he promoted the concepts and tools available to enhance the contractor input based on modeling capabilities. A small investment in learning to use Google SketchUp was all that was required to get us started in 2015. KMI has begun to use Tekla Structures as well for structural CMU models. Each project is reviewed for requirements and complexity to determine whether and what type of model to create.
For 7Seventy7, KMI used both software programs to create the masonry Building Information Models. Tekla Structures for the structural CMU as it is easier to include rebar and grout in that program than SketchUp. SketchUp was used for the decorative burnished block veneer because it is easier to label units for field personnel.
Communication Improves Process
Coordination. Models allowed for clash detection and better coordination. The Tekla model coordinated structural CMU installation with drawings of the mechanical contractor for opening locations and sizes. Layout and elevation drawings provided to field personnel included rebar layout, MEP openings, control joints and bond beam elevations. Potential clashes were eliminated and productivity improved for both parties.
Design Intent. Per contract, KMI Construction was required to submit shop drawings for the burnished veneer layout to ensure the architect’s design intent was being met. Shop drawing development of a model occurs in the Construction Phase and is known as LOD (level of development) 400 per American Institute of Architects (AIA) Document E203-2012, Building Information Modeling Protocol Exhibit.
The original veneer model submission had CMU laid out as a typical 1/3 running bond assumed as the design team’s intent.
Bond Pattern. Burnished CMU 8"x24" units created a pattern in the veneer not typical to a masonry wall. Typical patterns would be running 1/2 or 1/3 bond, but in this design, the CMU had a pattern with a step in it. Figure 2Adding to the complexity was the fact that there were three different colors of burnished CMU used. In reviewing the model, the non-typical step pattern was clarified for installation accuracy.
Material Selection. As the design and construction teams progressed through the approval process, several issues needed to be resolved prior to beginning construction. The design team’s drawings included full sized units (8"x8"x24") with finished ends. The CMU producer does offer 8"x8"x24" units, but not with finished ends. We worked with the design team to adjust the pattern to accommodate shapes and sizes of burnished CMU that were available. Even so, 44 different shapes were included in the design in two thicknesses (4" and 8") depending on what steel or backup was behind the veneer.
Based on the shapes and sizes available, issues with the pattern layout at transitions from one color CMU to another were able to be resolved. Working through the SketchUp model together, the teams decided to eliminate all stacked joints and adjust the pattern to accommodate the shapes and sizes of units available. Compromises were struck, including hand-polishing some units in the field.
Prior to modeling, these issues would have been encountered in the field, resulting in added non-productive field time to resolve.
Proactivity Benefits Crew, Bottom Line
By using the model to go through the approval process with the design team, KMI Construction saved 8% of the estimated material cost. The model helped to eliminate waste generally incorporated in the bid process. Selection of existing shapes and sizes rather than creating special shapes decreased material cost.
Using the model also eliminated add orders that potentially affect lead time, freight costs and additional charges for smaller quantities, saving time and money once construction began.
All layout completed prior to beginning installation of the burnished CMU eliminated potential rework due to an impossible pattern and allowed masonry personnel to be productive from the start. Layout images for every elevation were provided. More detailed views of CMU piers led to RFIs and layout issues that occurred during the shop drawing phase.
Masonry field personnel posted images in the job trailer and took drawings on site to resolve any questions related to layout issues throughout the installation process. Minor changes were able to be made to the layout due to field conditions. The model was adjusted accordingly and new drawings were distributed to field personnel almost instantly.
In addition to material cost savings, an estimated 8% was also saved in masonry labor costs compared to the estimate. It is challenging to determine how much of the 8% can be attributed specifically to the masonry models that were completed, but the models were no doubt a contributing factor.