The construction of the Perot Museum of Nature & Science in Dallas is an example of where technology makes building the nearly-impossible possible.
California-based Morphosis Architects’ design is a landmark for the Texas city, but to build that design has presented more than its share of challenges. Just ask anyone at Dallas-based BakerTriangle, the drywall contractor for the job. It is a one-of-a-kind building with many unusual and unique features, says Keith Giddens, the contractor’s director of virtual design and construction.
Take the lobby ceiling for example. “We had to invent something because a ceiling like that had never been done before,” he says. Aside from a computerized base model provided by the architect, BakerTriangle was given few details on what materials to use or how to construct the complicated 35,000 square foot ceiling.
The construction of the Perot Museum of Nature & Science in Dallas is an example of where technology makes building the nearly-impossible possible.
California-based Morphosis Architects’ design is a landmark for the Texas city, but to build that design has presented more than its share of challenges. Just ask anyone at Dallas-based BakerTriangle, the drywall contractor for the job. It is a one-of-a-kind building with many unusual and unique features, says Keith Giddens, the contractor’s director of virtual design and construction.
Take the lobby ceiling for example. “We had to invent something because a ceiling like that had never been done before,” he says. Aside from a computerized base model provided by the architect, BakerTriangle was given few details on what materials to use or how to construct the complicated 35,000 square foot ceiling.
The design calls for a ceiling that undulates and flows, free of segmented sections. To meet that tall order, the contractor started by pulling the 2D ceiling file from the computer model and transferring it to a BIM file to create 3D computer mockups. The result is a design comprised of 2 by 2 by 2-foot 12-guage wire mesh panels. The wires, which had to be bent to meet the wave-like forms specified by the architect, are welded at 1 inch on center.
Paramount to the design is that the fastening system holding the ceiling panels up was to be invisible to museum visitors. It helps give the ceiling a look of a “continuous wavy mesh,” Hatch points out. BakerTriangle’s solution was to develop a clip system that ties each of the corners of the panels together. That is easier said than done because the ceiling isn’t on a flat plane.
“We had to do a lot of fine tuning and we found out that without a grid system there is almost no tolerance during installation, so all the panels had to be precisely made,” says Giddens. Texas-based Kaspar Wire Works custom made the panels for BakerTriangle.
Electronic Assistance
To construct the ceiling’s complex geometry, the drywall contractor used robotic total stations—equipment normally associated with surveyors—to establish precise elevation points of the ceiling’s form and layout, says Giddens.
“Robotic stations are really good for complex layouts such as radiuses, weird curves and things like that,” he says.
Pablo Reyna, BakerTriangle’s project superintendant, says that was difficult to build. Averaging 200 to 300 ceiling elevation points per day with the RBS, Reyna’s crew took almost 9,000 elevation points to determine every pitch and slope of the ceiling as well as the height of the ceiling hangers. To achieve the same results manually would take months.
Reyna says in 10 areas of the lobby elevation, points were taken from subceilings (housing the MAP mechanical/electrical systems) that were installed prior to the hangers. “We did this so we wouldn’t have to hang the hangers from the deck underneath the floor and go through subceilings,” explains Reyna.
The subceilings are comprised of a standard 15/16-inch black T-grid system. From the grid system of the subceiling is a clip that attaches to the “T” to support 1/4-inch all-thread rods. At the bottom of the all-thread rods are clips that BakerTriangle developed to support the panel corners.
A logbook was kept with every hanger numbered. In the field Reyna had a crew of three cutting and fabricating the hangers and a fourth worker on a lift to install the hangers.
“When we got all the hangers up you could see the up and down rolls in the ceiling,” Reyna says. “There would be no way you could frame that ceiling without this technology.”
The BakerTriangle crew also installed 23 fiberglass lighted spherical shapes that hang below the wire mesh ceiling. “They look like floating asteroids,” Reyna says.
BIM Made It Possible
The ceiling installation was straightforward by comparison to its development and design largely because bugs were worked out during the mockups created with BIM.
“From the model and robotic station we were able to take the length of each of the clips and subtract that from the subceiling height to come up with a length for the clip assembly,” explains Giddens. The all-tread rods were cut in the field, based on the modeling.
Giddens suggests that without BIM, the ceiling would have been nearly impossible to build: “It was up to us to review the architect’s design, take it apart and figure out how to build it. BIM made it possible.”
“Technology has opened up a big door on what you can build now without having to worry about whether it will work or not because you can look at in 3D drawings to work out the bugs,” adds Reyna, who has a crew of about 20 of the company’s “best framers and drywall installers” on the job. “We’re doing more work with fewer people because we see it built (on a computer model) before we actually build it.”
The 180,000 square foot building is scheduled to open in September. BakerTriangle’s contract wraps up this summer. Overall, the drywall contractor will install about 700,000 square feet of drywall on five floors and about 27,000 square feet of exterior framing. For the museum’s conventional walls, 5/8-inch drywall is used; other areas require specialty products.
One of the museum’s three escalators is a case in point. The escalator runs through a tube-shaped enclosure made of a metal stud frame and drywall between the lobby and the second floors. The escalator’s design was “pulled” from the architect’s computer model and was sectioned up and measured to determine the top and bottom points. To complete the layout dimensions as the drywall crew framed the tube, BIM provided multiple pictures to form the shape of the tube.
“We had a lot of valleys, ups and downs that couldn’t easily be cut,” says Reyna.
Four by 8-foot sheets of drywall were cut to fit the curves of the enclosure, says Kyle Caviness, BakerTriangle’s project manager for the high-profile contract. On extreme curves, rather than use 1/2-inch drywall, the contractor employed three layers of high flex 1/4-inch drywall.
“Looking back, I can’t imagine how we would have done it without BIM,” points out Caviness.
The top escalator was difficult to complete because it runs outside the building. The tight working conditions eliminated the option of traditional scaffolding. Instead, BakerTriangle leased two compact lightweight lifts, one positioned on the ground floor plaza, the other on the roof, each with a reach of 95 feet. The structural steel was infilled top and bottom with metal stud framing and a metal panel system. The sides of the elevator are glass.
Oh, What a Ceiling!
BakerTriangle was retained as the drywall contractor two years ago at the design stage not just to figure out how to design and build the complex lobby ceiling but also for other features of the building. The ceiling in the museum’s 4,000 square foot theater is an example. Again, other than the architect’s base model, the contractor was provided with few details on materials or how to frame and complete that complex ceiling, explains Giddens.
Caviness says that while the theater is small-scale compared to the lobby, the level of difficulty was on a par, largely because the theater ceiling design also has a “very wavy” form that will be covered by stretched fabric.
“This ceiling is a set of compound curves in every direction,” Caviness explains. The first step in building it was to “pull the theater” out of the computer-generated base model and “slice it up in sections” in BIM to achieve proper dimensions for each section. The contractor sectioned the ceiling every 16 inches on center to create a layout of the profile. “Think of it like a loaf of bread, but no two slices (sections) are the same,” Caviness says.
The next step was to translate the BIM model to a buildable system. Giddens devised a substructure comprised of a sheet metal profile, extending up the walls and across ceilings. “In essence we were making a weird-shaped stud that will help to make the profile of the ceiling that the architect wants,” says the director of virtual design and construction.
It took about five weeks for the contractor to frame out a 12 by 12-foot mockup. Having ironed out the humps in the mockup, the ceiling and walls of the 60 by 80-foot theater can be framed in a mere one to two weeks, points out Reyna. “All we have to do is put the panels in order, snap them together, and screw them together—that was it,” he says. “Manually, the job would have taken five to six times longer, and we’d have had to have a lot more manpower.”
The profile is made up of 4 by 12-foot sheet metal sections (to fit the mechanical contractors requirements), each with its own shop drawing. Calculations for each section were fed into a CNC plasma cutting machine to make profiles to fit the ceiling slopes. Some of the sheet metal sections had to be cut into several pieces to fit the curves.
The sheet metal is suspended from the ceiling structure with conventional hangers. The walls are fastened directly to the substrate. Next, the sheet metal is covered with a layer of 1/2-inch drywall to provide a smooth surface for the fabric.
“If there is anything rough in the framing of the sheet metal, such as fastening screws, the drywall covers it up,” says Caviness. Some of the 4×8-foot drywall is “very cut up” to follow the curvature of the ceiling. Once the MAP fitout was completed, 1-inch rigid-board acoustical insulation was installed. Finally, the fabric will be stretched over the ceiling and walls and tucked and fastened at the corners through a fabric rail.
“As far as we know, a ceiling like this has never been done before either,” suggests Caviness. “Think of it as Keith’s (Giddens) brainchild. BIM was integral to pulling the ceiling job off. I can’t imagine doing it without it.”
On the Cutting Edge
BakerTriangle’s experience with BIM had a lot to do with it landing the contract. “Most general contractors are going in that (BIM) direction so it is an advantage to them to get more subs with technology experience on their team,” says Giddens.
Staying abreast of the latest in technology is a priority at BakerTriangle, he says. In mid-2010, the company invested in high-tech software and site tools that bring precision to wall layout. The tools include the robotic total station and controller and 3D CAD software.
“We’re pushing to get in earlier (at the design stage) on projects to have more influence on the correct way to build a job,” Giddens says. “For years architects have drawn in the way they think details should be put together, but that may not necessarily be how they are built in the field.”
So why aren’t more drywall contractors embracing BIM technology? It requires highly trained operators and it is expensive, points out Giddens. But it can be money well spent. Building a job virtually allows a contractor to work out bugs before going into the field.
“Anytime you build something a second time, you are a heck of a lot more efficient,” he says.
While it is still unusual to find a drywall contractor as comfortable with BIM as BakerTriangle and a handful of others in the Dallas–Fort Worth area, Giddens believes that it will become more commonplace in a few years: “There are still contractors out there who think this is a fad, but the guys we work for are pushing it so we have to stay with them, if not ahead of them.”
Other high tech tools are an integral part of BakerTriangle’s contract at the Perot Museum and other projects. The latest version of on-screen take-off equipment is at hand, and most of the company’s field foreman carry iPads, not toolbelts. “When we pick up a project we start ‘BIM-ing’ it so they can see the project in 3D before they build it,” explains Hatch, adding that keeping up with technology is paramount in the business.
Giddens says the contractor’s experience with BIM has allowed it to work directly with general contractor Balfour Beatty Construction at the pre-bid and post-bid stages.
Don Procter is a free-lance writer in Ontario, Canada.
