The Cascading Timber Roof of the Bloomberg Student Center

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Located at the heart of John Hopkins University’s Homewood Campus, the Bloomberg Student Center serves both as the social hub of student life and as a new gateway to the campus. The approximately 143,000 square foot (13,300 square meter) facility accommodates a broad range of student-oriented functions, including a food hall, a 200-seat theater, multipurpose rooms, lounges, and informal gathering spaces.

The architect, Bjarke Ingels Group (BIG), envisioned the building as a communal "living room" for the student body. Interior spaces flow seamlessly into the entrance plaza, strengthening the connection between the campus and the adjacent Charles Village neighborhood. The gently sloping topography of the site is reflected in the cascading roofscape and monumental stairways, creating fluid transitions between the various building volumes and programmatic functions.

The student center comprises four levels. Above grade, the building consists of 29 transparent, timber-framed cubic volumes, while the below-grade levels are constructed in reinforced concrete and accommodate the theater, service areas, and other support functions.
The main engineering challenges in the design of the building were the complex lateral force resisting system as well as the interaction between structural deformations and other movements, such as swelling and shrinkage, to the envelope design.

The characteristic cascading roof geometry is supported by a regular post-and-beam framing system constructed from glued laminated timber (glulam). Uniform beam spacing and standardized member sizes enabled a highly rationalized structural system despite the complex architectural form.

The glulam members were manufactured from spruce–pine–fir (SPF), conforming to the North American 20F-1.5E stress grade and supplied in architectural appearance grade. Beam depths range from approximately 12-48 inches (305 mm to 1,220 mm), with maximum spans exceeding 70 feet (21 m).

Structurally, the glulam beams support the roof deck while simultaneously contributing to the building's lateral load-resisting system. Acting as horizontal collectors, they transfer wind and seismic forces as axial loads toward the reinforced concrete cores, cross-laminated timber (CLT) shear walls, and steel bracing systems.

The vertically offset roof planes are interconnected by continuous glazed clerestories. These repeating skylight bands admit daylight deep into the interior, significantly reducing the reliance on artificial lighting while reinforcing the architectural expression of the cascading roofscape.

The primary glulam framing supports a roof deck constructed from dowel-laminated timber (DLT) panels, which span between the glulam beams at a regular spacing of 14 feet (4.26 meters). The panels were generally designed as continuous multi-span members.

Thanks to the regular structural grid, most DLT panels are only 5.5 inches (140 millimeters) thick, although localized thicknesses of up to 11⅛ inches (283 millimeters) were required where structural demands increased.

Several roof planes cantilever up to 15 feet (4.6 meters) beyond the supporting structure to provide passive solar shading, particularly along the south facade—substantially reducing solar heat gains and improving the building's overall energy performance. Because DLT panels can span in only one direction, cantilevers perpendicular to the panel span were achieved by integrating rectangular hollow steel sections (HSS) within the roof build-up.

The exposed DLT soffit also contributes to the building's acoustic performance. Concealed acoustic foam strips inserted between the timber laminations achieve a Noise Reduction Coefficient (NRC) of up to 0.70, allowing the exposed timber ceiling to function simultaneously as an architectural finish and an effective sound-absorbing surface.

To provide in-plane diaphragm action, the upper surface of the DLT panels is overlaid with ¾ inch (19 millimeter) plywood sheathing. Service distribution was coordinated within the roof depth by intentionally spacing adjacent DLT panels apart to create continuous cable raceways. These service corridors were subsequently enclosed above by the plywood diaphragm and below by narrow DLT cover strips, preserving both the structural diaphragm action and the uninterrupted appearance of the exposed timber ceiling.

The building's lateral load-resisting system comprises three reinforced concrete cores, eight CLT shear walls, and multiple steel cross-bracing systems formed by tension rod assemblies.
Because the various lateral-force-resisting elements differ significantly in stiffness, accurately determining their respective contributions to the transfer of wind and seismic loads required a detailed assessment of the stiffness characteristics of each structural component.

Particular attention was given to the determination and implementation of realistic stiffness parameters for the CLT shear walls. Accurate representation of these elements was essential to prevent the numerical model from overestimating their stiffness and consequently underestimating the load demand on the steel bracing system.

The first step involved verifying the CLT wall configurations complied with the requirements of the Special Design Provisions for Wind and Seismic (SDPWS-21). These provisions included, among others, limitations on the aspect ratios of multi-panel shear walls as well as detailing requirements governing the number, arrangement, and design of mechanical fasteners. Subsequently, an Excel-based calculation tool was developed following the methodology presented in a design example published jointly by FEMA and the American Wood Council (AWC). The spreadsheet quantified the individual deformation components contributing to the overall displacement of each CLT shear wall, including:

Based on these deformation mechanisms, the total lateral displacement of each shear wall under a unit horizontal load was determined analytically. The wall stiffness properties in the FE model were calibrated iteratively until the numerical displacements matched the analytically derived values. This calibration procedure enabled a realistic upper- and lower-bound assessment of the load sharing between the CLT shear walls and the steel bracing system, resulting in a more reliable prediction of the building's lateral force distribution.

The glulam structure was detailed with concealed connections: Concealing the connection hardware not only reinforces the architectural expression of the exposed timber but also enhances the fire performance of the steel components. Where steel connectors were required, they were protected by timber cover plates, providing a fire-resistance rating of 60 minutes while maintaining the clean visual appearance of the exposed timber structure. Bolted steel connections were designed to maximize prefabrication, enabling rapid on-site assembly with a high degree of dimensional accuracy. This construction strategy also facilitates future disassembly, allowing the primary structural timber components to be removed, reused, or recycled at the end of the building's service life. The selection of DLT roof panels, in place of CLT, further reinforces the project's design philosophy of Design for Disassembly (DfD). Since DLT panels rely exclusively on hardwood dowels rather than adhesives or metal fasteners, they can be dismantled more easily, improving the potential for material reuse and supporting a circular approach to construction.

The highly transparent glazed facade is supported by a custom-designed steel curtain wall system consisting of laser-welded mullion profiles with insulated solar control glazing. The slender framing members span vertically up to 30 feet (9 meters) while maintaining exceptionally narrow sightlines, maximizing transparency and preserving uninterrupted views between the interior and the surrounding campus. Continuous clerestory glazing between the staggered roof planes introduces daylight deep into the building, while the generous roof cantilevers provide passive solar shading. The varying depths of these overhangs were optimized through detailed solar radiation analyses to balance daylight availability with thermal performance throughout the year. Because the DLT roofs extend across the building envelope line, a special detail was developed to provide a continuous air and vapor seal through the DLT with prefabricated sealant dados between each lamination. Bird-friendly glazing is employed across the entire facade, reducing the risk of bird collisions without compromising the building's architectural transparency.

The anticipated structural movements required close coordination between the timber frame and adjacent facade systems, particularly at the glazed clerestories. Close attention was given to the long-term behavior of the glulam roof structure, because timber is hygroscopic and exhibits both moisture-related dimensional changes as well as long-term creep under sustained loading. Anticipated creep deformations and timber shrinkage were carefully evaluated during the design process. To compensate for long-term deflections of up to 1 inch (25 millimeters), the glulam beams were fabricated with intentional precamber.

Curtain wall joints and glazing tolerances were designed to accommodate timber shrinkage of up to ¾ inch (19 millimeters), in addition to both short-term elastic deflections and long-term creep of the supporting structure.

Detailed movement studies informed the design of the clerestory glazing system, allowing differential deflections between adjacent roof levels to be accommodated while minimizing the required joint widths and preserving the clean architectural appearance.

Beneath the exposed mass timber superstructure lies a four-level reinforced concrete substructure embedded within the site's gently sloping topography. This below-grade construction accommodates the building's theater, service areas, and infrastructure while providing the structural foundation for the timber superstructure above. The foundations comprise isolated spread footings bearing directly on bedrock, supplemented by reinforced concrete mat foundations beneath the lateral-force-resisting cores.

Material selection, renewable energy generation, and passive environmental design strategies collectively enable the Bloomberg Student Center to achieve LEED Platinum certification. The building's deep roof overhangs provide effective passive solar shading, substantially reducing cooling loads by limiting direct solar heat gain during the summer months. Complementing this passive strategy, the rooftop photovoltaic arrays generate approximately 40% of the building's annual energy demand, significantly reducing operational carbon emissions.

The extensive use of mass timber further lowers the project's embodied carbon by storing atmospheric carbon dioxide within the structural wood products throughout the building's service life.

In addition, the reinforced concrete incorporates CarbonCure technology, which permanently mineralizes captured carbon dioxide within the concrete during production, further reducing the project's overall carbon footprint. This more sustainable concrete specification had no noticeable impact on concrete quality and tested strength in the project.

The Bloomberg Student Center opened October 2025, welcoming students at the beginning of the Fall 2025 semester. Today, the building serves as a vibrant center of student life as well as a new architectural landmark for the Homewood Campus. By combining expressive mass timber architecture, advanced structural engineering, and ambitious sustainability goals, the project establishes a new benchmark for high-performance academic buildings and demonstrates the potential of contemporary timber construction for large-scale institutional projects. ■

About the Author

Florian Meier, PE, is a structural engineer and Director at knippershelbig. After 10 years working in New York, he is now co-leading the Berlin office and is Professor i. V. at Potsdam School of Architecture.

Shamil Lallani is a Senior Associate specialized in enclosures at knippershelbig in New York. He has degrees in structural engineering and architecture and is previously a visiting lecturer at CUNY New York City College of Technology.

Christian Rieser, PE, SE, P.Eng., is a licensed professional and structural engineer and Director of knippershelbig in New York. He is currently Assistant Adjunct Professor at the Cooper Union’s Irwin S. Chanin School of Architecture.