Paying attention to details
In particular, the design team paid close attention to the color and size blend of the ashlar sandstone exterior walls. “The mock-up gave us an opportunity to verify that the color blend and texture we were aiming for was achieved,” said Erickson, adding that the mock-up also allowed them to make sure that the criteria for the lay-up pattern was followed.
Reiterating Quigley’s words, Erickson explained that the University Facilities Planners had developed very specific criteria and parameters for laying up the ashlar pattern. In addition to setting a maximum and minimum thickness of any individual stone and maximum thickness to length ratio, there were specific rules set for convex versus concave split faces, maximum number of stone courses abutting “jumpers,” a maximum and minimum range of dimension that the stone face should extend outward beyond the plane of the mortar joint, and outside corners are struck vertically in alignment.<br><br>
“The mock-up gave us an early indication that the mason understood and was able to execute the criteria,” said the architect. “It also gave us an opportunity to verify the color consistency of the limestone accents and that they were being placed as detailed.”
Overall, Erickson explained that they were fortunate to find a good mason. “Although the masonry subcontract was competitively bid through the Construction Manager/General Contractor, we pre-qualified the list of bidding masonry subcontractors - each of whom had some experience working on the CU-Boulder campus,” he said. “We are fortunate that the Denver market has many highly skilled masons.”
Before work on the project began, the design team visited several area stone yards to determine what colors were being extracted from the local Colorado quarries, according to Erickson. “We were looking for a level of consistency in color for each type we were considering specifying as part of the overall blend,” he said.
One of the most challenging aspects of the project, in regards to the stonework, was the schedule, said Erickson. “With the smaller stone sizes and patterning criteria and the production of stone peaks at about 25 square feet per mason per day, keeping pace with the expectations of the overall construction schedule was the most challenging,” he said. “Fortunately, the mason was experienced with the requirements from previous work on the campus and did not need a lengthy learning curve to get multiple crews up to speed.”
In total, construction of the Koelbel Building expansion was completed in 17 months. “The design team had a considerably shorter time to design and document the project; and due to time restrictions, we issued three separate bid packages of construction documents in fast-track fashion,” said Erickson.
According to both architects, the Business School has been elated with the success of the project. “The Dean recently reported a doubling of enrollment in the school’s executive education program since they moved into the completed building,” said Erickson.