solid wood shells

(x)

Berkeley, CA
publication

Supervisor: Paul Mayencourt

submitted to the International Association for Shell & Spatial Structures, Mexico City, MX 2025

Since its development in the early 19th century, softwood lumber has become the predominant construction system in the United States [1]. Its widespread use in the built environment and critical role in forest management have significantly impacted material flows, energy consumption, and emissions [2][3]. This paper expands on novel applications of dimensional softwood that could drive a fundamental shift in the environmental, social, and economic impacts of the contemporary lumber industry [1][4]. As an accessible construction system that is affordable, flexible in form, labor and composition, dimensional lumber inherently carries great potential for sustainable design practices. Despite its adaptability, dimensional lumber is primarily used as stiff and straight framing elements, leading to both narrow application and narrow economic assessment of wood. Novel applications of wood can inform and expand current manufacturing and forest management practices, creating economic incentive for wood currently seen as waste. This paper examines the potential of using dimensional lumber for nail-laminated solid wood shells, adding value through new systems of assembly. Laminated shells are based on a lamination principle developed in the early 19th century, combining several sawn soft lumber sections with nails into a large load-sharing panel, known as mechanically laminated decking [5][6]. Kermani and Freedman emphasize that lamination optimizes load distribution, allowing for the effective utilization of lower-grade and variably sized timber. By dispersing natural strength-reducing characteristics throughout the panel, this method enhances structural efficiency and minimizes material constraints [6]. With deficiencies spread homogeneously throughout the panel, this system accommodates the use of lower grade wood, supporting the application of recycled softwoods and incentivizing the use of small-diameter trees with inherent lower mechanical properties [3].

Furthermore, laminated shells might allow for the application of green and wet wood, reducing the drying time. According to Bergman and colleagues, drying consumes the highest proportion of embodied energy in wood products manufacturing. The work of Bergman, et al also shows that wood fuel accounts for 87 percent of energy use at the mill [2]. Additionally, the moisture content of wood affects its ability to flex and bend [7]. This has potential for new applications of a material conventionally seen as waste which in turn can inform and enhance geometric expressions true to its inherent properties. Neumann and colleagues have shown that the creation of curved forms as well as its machinability make softwood very suitable for realizing the new experimental forms of contemporary
architecture [7].

Finally, advancements in three-dimensional modeling and visualization software have significantly enhanced the integration of material properties into the design process. While material-driven design is not a novel concept, its effective implementation necessitates close collaboration between architects, engineers, and builders to conceive innovative fabrication methods and structural geometries. This interdisciplinary approach aligns with the methodologies of distinguished figures such as Antoni Gaudí, Félix Candela, Eladio Dieste, and Frei Otto, all of whom systematically investigated the relationship between material behavior and geometric efficiency [8][9][11].

This research learns from the legacy of architects and engineers who have harnessed material characteristics to develop structurally efficient and aesthetically expressive shell constructions. It first explores methods for deploying dimensional lumber in solid shells to expand on its singular application and promote use of lower grade reclaimed wood. Next, we lay out structural and geometric constraints of using straight elements to construct curved and doubly curved surfaces. The study concludes with the realization of full-scale physical prototypes as well as digital models of solid wood shell designs.

This research contextualizes key advancements in shell design and engineering, highlighting Candela's mathematically optimized geometries and Frei Otto's experimental grid shells to illustrate how material properties inform structural behavior. While unreinforced masonry and concrete shells rely on compression-only geometries, wood shells can accommodate both compressive and bending forces, as demonstrated by historical precedents such as De l’Orme’s segmented arch system and Gaudí’s parabolic timber vaults.

This study explores the use of dimensional lumber in solid wood shell construction, employing a segmentation and lamination approach to integrate smaller wood sections. This method facilitates the utilization of irregular or lower-grade wood sources, thereby enhancing resource efficiency and reducing waste in timber fabrication. By formalizing the design constraints, the study explores the first steps to design doubly curved shell structures made from dimensional lumber. The scope for the structural analysis is limited to a flat nail-laminated panel acting in pure bending. The findings from the digital model and full-scale prototypes highlight key structural parameters such as span to rise ratios, curve segmentation, and nailing zones, that influence material efficiency and constructability. With an emphasis on low-tech fabrication methods, this project offers a framework for optimizing irregular or lower-grade wood sources, contributing to sustainable resource utilization and expanded applications of dimensional lumber in architectural design.

Future research should address material performance, including the impact of joint design and segmentation on overall shell integrity, as well as the potential of developing a modular shell panel and its connections to a broader structural system. A form-finding method, including the behavior of the material anisotropy and joint stiffness of the assembly system should be developed to further asses the structural potential of this shell system. Additionally, strength analysis, the automation of nailing patterns and development of larger scale physical prototypes are critical in advancing this line of research. Geometric studies may explore component geometries and modular configurations. Further work on affordability strategies should focus on optimizing geometry and standardizing elements to enhance cost efficiency. By integrating computational form-finding with material-conscious design strategies, this research advances sustainable timber construction and offers new possibilities for adaptable, resource-efficient shell structures.

[1] American Framing. (2022). Pavilion of the United States at the 17th International Architecture Exhibition –la Biennale di Venezia. https://americanframing.org/ Accessed May 22, 2025.
[2] Bergman, R. D., & Bowe, S. A. (2010). Environmental impact of manufacturing softwood lumber in northeastern and north central United States. Wood and fiber science. Vol. 42, suppl. 1 (2010): p. 67-78., 42, 67-78.
[3] Mayencourt, P., & Swagemakers, J. (2025). DIY mass timber: development of low-tech and low-cost structural mass timber manufacturing to support forest utilization in California. Architecture, Structures and Construction, 5(1), 1-11.
[4] Khatib, J. (Ed.). (2016). Sustainability of construction materials. Woodhead Publishing.
[5] Hong, K. E. M. (2017). Structural performance of nail-laminated timber-concrete composite floors (Doctoral dissertation, University of British Columbia).
[6] Kermani, A., & Freedman, G. (2005). Performance of a stress-laminated-timber arch bridge. Proceedings of The Ice - Bridge Engineering. 158. 155-164. 10.1680/bren.2005.158.4.155.
[7] Neumann, O., Hunter, J., Meyboom, A., & Tannert, T. (2015). Timber Shell: Wood in Building. Journal of Engineering and Architecture. 3. 10.15640/jea.v3n2a15.
[8] Matthews, H. (2009). Felix Candela: Engineer, Builder, Structural Artist by Maria e Moreyra Garlock & David Billington. The Art Book.
[9] Pedreschi, R. (2019). The work of Eladio Dieste and its impact on engineering and architectural education.

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