The pristine slice of Ozark countryside set aside for the Scott Family Amazeum, in Bentonville, Ark., was rife with potential. But there was one design caveat. The 50,000-square-foot children’s museum would sit at the entrance to the campus anchored by the iconic Crystal Bridges Museum of American Art, by Moshe Safdie, FAIA. And because the two institutions largely share the same donor base, “there was a sense that this building needed to tip its hat and be respectful” of Crystal Bridges, says Reb Haizlip, AIA, founder and design principal of Memphis-based Haizlip Studio.
But the studio still wanted the new museum to be distinctive in its own right, so it topped the three-story main entrance and lobby atrium with a soaring glulam-pine butterfly roof whose swooping, asymmetrical concave form is a playful counter to the convex roofs of Crystal Bridges.
The Amazeum has a steel structural system, with columns spaced every 30 feet along the 150-foot-long lobby. Spanning the lobby’s 25-foot width and tying in each pair of columns are 18-inch-deep glulam joists, each of which supports four 18-inch-deep-by-10.5-inch-wide glulam beams that appear to run continuously along the full length of the lobby before turning up to create the gentle swoosh of the roof. In reality, the structural members comprise 30-foot-long segments that butt together at the joists. They taper from 24 inches deep at the apex of the concave curve to 14 inches at their exposed ends at the roof eaves, and are capped with zinc cladding.
For the column-to-joist and joist-to-beam intersections, Haizlip Studio used steel plates, left exposed. “One of the requests of the owner was that connections [be] bare, lean, and muscular so that kids could understand the physicality of building,” Haizlip says.
Above the beams, the lobby ceiling is finished with 3-inch-wide tongue-and-groove pine decking, painted with three coats of clear, spar urethane varnish with a UV inhibitor. The ceiling is nailed to a plywood deck, which is topped with a layer of 4-inch-thick rigid polyisocyanurate insulation board and covered by a standing seam metal roof. Painted in dark gray, the roof matches the color of the hand-folded zinc cladding on the building’s lower exterior walls. The studio features zinc throughout the project because of Northwest Arkansas’ former history as a hub for zinc and lead mining.
Haizlip Studio originally envisioned the glulam roof as a composite structure, with both the joists and beams on one plane, instead of stacked. It was an elegant design requiring complex structural connections that were ultimately deemed too expensive during the value-engineering phase. The designers conceded, except at the west-facing main entrance, where the roof eave becomes a striking, 34-foot-long canopy. “I put my foot down,” Haizlip says. “I said, ‘Here, we have to have the composite structure.’ And you can see the difference.”
Transitioning between the stacked roof assembly inside and the composite wood structure outside created a challenge. “It was that moment of, ‘I’ve got to make this work,’ ” Haizlip says. The transition takes place at the curtainwall façade, where the outermost glulam joist also appears as a fascia above the entrance. Above the joists and below the roof deck, filling the interstitial spaces between the beams members, is a wall constructed from exterior sheathing wrapped with a continuous weather barrier and zinc cladding, and framed by metal studs with batt insulation in between. The metal studs attach to, and are aligned with, the width of the glulam joist below, and a deflection head track that ties into the wood decking above.
In spite of the deviations from Haizlip’s original vision, the lobby’s sweeping roof allows extensive daylight through the atrium’s curtainwalls, transforming the narrow volume into an inviting foyer that welcomes families from near and far to the museum. “In the end,” Haizlip says, “if the kids are happy, and they smile, then we’re good.”