Wood is a highly regarded building material for many reasons. Its versatility is unrivaled. It is a natural product and it is renewable, two qualities that net it "green" points. With its infinite grain patterns, inherent character in knots and wide spectrum of natural colors, it's also gorgeous. Less notorious are wood's acoustic qualities, which only reinforce its usefulness in buildings where people and sound come together. A prominent example of wood performing all of these functions is Helzberg Hall, a concert hall that is part of the new Kauffman Center for the Performing Arts, a sprawling 285,000-square-foot complex in Kansas City, Mo.
To the building's north is downtown and to the south is Kansas City's warehouse district; also nearby is the city's entertainment district. As a result of its location, the Kauffman Center serves as a cultural linchpin for the city known as the "Paris of the Plains." At the building's front is what Safdie Architects' Partner Isaac Franco calls "the front porch," a large, open lobby area behind a 65-foot-high by 330-feet-wide glass wall that provides patrons with a fantastic 180-degree view of the city beyond. "We wanted to have a very open, very light lobby area," Franco says, "and it is almost like a window into the building from the outside so people walking by or driving by can see the activity in the lobby. That is our connection to the city. We wanted synergy between inside and outside, and we wanted to take advantage of that expansive view that the site afforded us. It is a window to the arts."
Once inside the building, patrons seeking the finest in the musical arts will visit Helzberg Hall. With seating for 1,600, the building resembles a multi-tiered curvilinear bowl. The hall was designed in the "vineyard" style for orchestral halls, so the audience surrounds the performance stage on all sides, and there are no balconies-a design that serves to bring the audience closer to the performers. Nearly the entire space is clad with wood, with Douglas fir lining the walls, riftsawn red oak underfoot in the seating areas, and a stage crafted of Alaskan yellow cedar. Safdie and his colleagues picked wood as the primary building material in the hall for reasons easy to comprehend: performance and looks.
The Perfect Instrument
It is easy to think of Helzberg Hall as just one component of the Kauffman Center, but it is more than that. The hall is actually an independent building within the arts center since each component—Helzberg Hall, the Muriel Kauffman Theatre and their encompassing shell—has its own foundation and utilities. This way, sound within each component can be better isolated and acoustically optimized.
To acoustically optimize an enclosed space, the absorptive and reflective properties of its building materials must be properly balanced. Whereas bare concrete reflects too much noise, leading to excessive reverberation, or echoes, a room lined entirely with carpet absorbs too much noise, causing music to sound flat. This is why wood is a preferred material when acoustics are paramount. "Acousticians don't like the idea of carpet flooring in a hall," says Franco, who managed the Kauffman Center project for Safdie Architects. "Wood is a hard surface but gives a coloring and mellowing to sound. Wood has some porosity and hardness so it gives you a richness that you wouldn't get from a tile floor ... We wanted to build the perfect instrument," he says. As for the other factor-looks-Franco may as well be preaching to the choir: "In terms of aesthetics, wood is much superior to a very hard concrete floor or any type of stone material."
Since there are no balconies-for acoustical reasons-seating levels in Helzberg Hall are tiered. To fit with the overall curvilinear design theme, seating rows are curved. Adding to the difficulty of installing flooring in this tiered seating area were HVAC vents cast within the concrete. Essentially, the flooring within the seating area can be viewed as a large, curvilinear staircase with holes-for the HVAC vents-in the treads.
The Installation Process
Bob Kenney and his crew at Lenexa, Kan.-based Acme Floor Company Inc. started the massive wood flooring project by grinding the freshly poured concrete flat. Due to the complex curves, they next used a laser transit to gather precise dimensions of the treads. To mark the location of each HVAC vent, Acme's Foreman Henning Mikkelson devised a system where each hole was plugged with a marker that would be picked up by the laser transit. "With the transit, we shot the front edge of the curve and the back edge," Kenney says, "and then we shot each one of those little plugs." Back at the shop, Acme input the transit data in the CNC machine and cut the ¾-inch plywood subfloor complete with the HVAC holes. Then the material was brought on-site and fastened to the concrete using ¼-inch driving pins. They also installed a sub-riser system of ½-inch MDF. Those two systems—subfloor and sub-riser—were joined with pocket screws so that the wood flooring installed over it would remain level.
Next, Kenney and his crew worked to install the seating-area flooring over the subfloor system. They started with more than 20,000 square feet of raw quartersawn red oak lumber and brought it to their own floor-manufacturing facility. "Almost everything we install, we manufacture ourselves in Kansas City," he says, and it is branded with the Missouri Hardwood Products name. The raw material was milled into tongue-and-groove plank flooring, measuring ¾ inch thick by 5 inches wide. Due to the complexity of the seating area, Kenney did not want to painstakingly cut each flooring board on-site, so the boards were first glued at the sides and pre-assembled into panels. "The panels were 4 feet wide and 12 feet long," Kenney says. "We laid those on the CNC machine, and then we cut the back radius and the front radius and assigned it a 'piece mark' so we knew exactly where they were going." The CNC machine also plunged a small center hole where each HVAC vent was located.
Those panels were brought on site and then fastened to the subfloor with adhesive; biscuit joints secured the panel ends. Then Kenney's crew used a router to cut holes for all of the HVAC vents. Between the panel and bottom of the sub-riser, Kenney left a ½-inch gap for expansion. On the outside of the sub-riser, a ½-inch MDF prefinished oak veneer riser was installed. Next came the sanding work and then stain and waterborne finish; to accent the actual stairs in the aisles, Acme Floor Co. gave the stair bullnosing a darker stain. "The nosing was stained a little bit darker so it would identify the tread itself," Kenney says. "Otherwise, the wood would all run together, so it was a safety issue."
In addition to installing the wood flooring in the seating area of Helzberg Hall, Acme Floor Co. was responsible for installing the oval-shaped performance stage platform, as well. The stage's hallmark is a set of mechanical risers that allow for quick layout changes in order to suit a variety of musical performances, from solo concerts, to chamber music, to full orchestra. Over the steel stage legs, Kenney and his crew installed a grid of big timbers, and over that they installed a sleeper system using precise measurements gathered with the laser transit. For acoustical reasons, Safdie Architects specified the stage floor be made of 1¾-inch-thick Alaskan yellow cedar that, again, Acme milled itself. With the sleeper system in place, Acme straight-laid the entire platform, securing the 5-inch-wide cedar planks to the sleepers using 3-inch finish screws inserted on a 45-degree angle right above the tongue. "We didn't use nails because we knew that stage would see a lot of movement, and eventually they could work their way out," Kenney says.
The crew next used a router to cut the outlines of the risers from the stage platform. "We've got some real experienced carpenters," Kenney says. "We set up a radius rod already knowing the tangent points for the risers, and then we cut through it with the router using a flush-cut bit." Moving down about a quarter-inch at a time, it took several passes with the router to get through the cedar. To improve the aesthetics of the risers, Kenney and Project Manager Randy Hamilton did two things: First, they designed cedar nosing to wrap the board ends of the cedar on each riser. "It was like each one of those risers had a band around it," Kenney explains. Second, they installed a two-layer skirt to conceal the extenders; the sub-layer consists of ½-inch MDF, and the outer layer consists of a ½-inch urethane-prefinished maple veneer. To finish the stage platform, Kenney and his crew applied two coats of tung oil.
Since Acme Floor Co. straight-laid the platform, individual planks span the risers, so there are no visual breaks from riser to riser. "The board you see on one riser is a continuation of another board on the next riser," Franco explains, "and when it's flat, you have a continuation of the same boards."
Attending to Detail
It is this type of attention to detail that bolsters Franco's belief that Helzberg Hall is itself the perfect instrument, and that is an idea that Kenney and his crew kept with them throughout their time working on the project, a span of about 15 months. "This was a complicated project," Kenney says. "At one of the very first meetings we had, it was discussed that we would be building a violin; we would not just be building a box." As a result, Kenney and his team approached the project with extraordinary planning, providing numerous unspecified mockups in advance. "As a team," Kenney says, "we really worked hard at solving problems ahead of time, and all the planning we did paid off in a big way. We always strive to make sure the architect knows what they are getting ahead of time."
Safdie Architects' Franco explains that work on the Kauffman Center for the Performing Arts spanned about 10 years. "It's a performing arts center," Franco says, "and those are always complicated buildings to work on. It is a very well-crafted and very well-executed building. It took a little longer than a normal project to build and design, but we are still very pleased with the results." With a perfect instrument made from the perfect building material, his sentiment is perfectly clear.
Project DetailsArchitect: Safdie Architects (Somerville, Mass.)General contractor: JE Dunn Construction (Kansas City, Mo.)Raw lumber supplier: Frank Miller Lumber Co. (Union City, Ind.)Wood flooring manufacturer & installer: Acme Floor Company Inc. (Lenexa, Kan.)Adhesive manufacturer: Bostik Inc. (Middleton, Mass.)Finish manufacturers: Bona US (Aurora, Colo.) & The Hope Co. Inc. (Bridgeton, Mo.)