Airport designs are often characterised by their functional yet sterile environments evoking images of bustling crowds, long queues and the stress of navigating through extensive, impersonal spaces. However, with its new main terminal expansion, Portland International Airport (PDX) in the US, redefines this experience by featuring a grove of mature trees beneath a sinuous mass timber roof which is punctuated by numerous skylights. Conceived by Oregon-based ZGF Architects, PDX in Portland embraces biophilia—the innate human affinity for nature—turning the airport journey into an evocative walk through a forest overstory. This transformation elevates the passenger experience and sets a new benchmark for airport design that harmonises utility with an immersive sense of place.

As a distinguished name in sustainable and regenerative design, ZGF Architects has consistently served as the airport's main architectural partner since 1965, overseeing multiple remodels and expansions. The recent renovation of the 10,00,000 sqft facility aims to double the airport’s capacity to serve up to 35 million passengers annually by 2045. “One of the most significant project challenges for PDX was to keep the airport fully operational during five years of phased construction, most importantly the check-in lobby and security checkpoints,” says the design team. In response, the American architects repurposed much of the existing infrastructure and strategically prefabricated elements to allow the airport to grow in place while maintaining its functionality and seamless operation.

Pursuing the intimate scale and local character of the old airport, ZGF planned the terminal into smaller, human-scaled spaces that echo the city’s tree-lined streets and parks. This approach—rooted in the city's urban planning principles—mimics Portland’s walkable neighbourhoods flowing intuitively from the ticket hall to security checkpoints. “With the new PDX, we wanted travellers to know they were in the Pacific Northwest before they even left the airport. And for locals, we wanted it to feel like home,” shares Vince Granato, Chief Projects Officer at the Port of Portland.

Pre-security, a public marketplace offers regional goods, dining and stadium seating, while post-security, the terminal accommodates tree-lined pathways and urban furniture that invite travellers to pause and reflect.

A defining feature of the decade-long sylvan project is its pioneering use of timber, harvested from the sustainably managed forests within a 300-mile radius. Over 3.5 million board feet of Douglas fir wood was sourced from small landowners, community forests and tribal lands across the Pacific Northwest region for constructing the undulating roof, parquet flooring, concessions and feature walls. These features are connected by 34 towering Y-shaped columns, reduced from the original 670 to further open the space. Fabricated from 1-inch plate steel and filled with thermal grout for fireproofing, these columns rise 55 feet and hold the 18-million-pound, 400,000-square-foot prefabricated architecture in place.

In line with the firm’s ‘Forest to Frame’ approach, which emphasises sustainable material sourcing from forests and craftsmanship on site, the nine-acre sculptural timber roof envelopes the terminal's nine blocks that have been added over the decades, into a singular, cohesive structure. This parametric ceiling features a mass-plywood roof diaphragm, glulam beams and 3 x 6-foot timbers for the lattice, with concealed rectangular cassettes integrating mechanical, electrical and plumbing systems. The wood architecture further scoops out 49 skylights which provide about 60 per cent of the terminal’s illumination. The public architecture showcases the region’s traditional weaving techniques while setting a new standard for sustainability and craftsmanship in infrastructure.

In collaboration with New York-based Terrapin Bright Green and local studio PLACE landscape architects, ZGF aimed at creating a calming environment to ease the stress of air travel, by incorporating natural elements throughout the terminal. The team strategically installed 72 large trees and 5,000 plants along with cascading gardens, as part of the landscape design to resemble a city park that is “warm, inviting, comfortable and relaxing,” as per the press statement. “The landscaping provides a sense of wandering through a forest and acts as a wayfinding tool that guides passengers from security checkpoints to their ultimate destinations,” says the design team.

According to an official statement by ZGF Architects, “The decision to reuse much of the existing terminal, along with using wood and optimising steel and concrete, enabled a 70 per cent reduction in the embodied carbon of the structure compared to building an entirely new terminal.” This approach, along with the use of an all-electric ground-source heat pump system, allowed the main terminal to double in size while cutting energy use per square foot in half. Portland International Airport further encompasses meticulous sustainable design strategies such as the use of high-performance façade, LEDs and strategic daylighting to reduce energy consumption; and low-flow fixtures for lower water use by 58 per cent. Additionally, the timber design is built to endure a 9.0 magnitude earthquake, with Y-shaped columns designed to absorb seismic movement, further enhancing the project’s sustainable architecture.

The expansion of the Portland International Airport establishes a new roadmap for future airports. As Sharron van der Meulen, ZGF Managing Partner puts it, “The design evokes the best of our region, yet offers other airports a new model for how to expand and renovate in place to meet the travel demands of the future generations." The second phase, wrapping up by early 2026, will expand post-security spaces on the north and south ends of the terminal and house new retail spaces and dining areas, to enhance the travel experience and capture the vibrant spirit of Portland, a city distinguished for its environmental consciousness and urban culture.

Featuring expansive and innovative roof structures, previous airport designs published on STIR include Bengaluru's Terminal 2 by Skidmore, Owings & Merrill (SOM), as a green oasis integrating nature, sustainability and culture to create an experiential paradise; and the starfish-shaped complex of the Beijing Daxing International Airport in China by Zaha Hadid Architects.

Project Details

Name: Port of Portland, PDX Airport Main Terminal Expansion
Location: Portland, Oregon
Client: Port of Portland
Architect: ZGF Architects
Interior designer: ZGF Architects
General contractor: Hoffman Skanska Joint Venture 
Structural Engineer: KPFF Consulting Engineers (primary), Arup
Mechanical/Electrical/Plumbing: PAE Engineers (primary), Arup
Mass Timber Trade Partner: Swinerton Mass Timber
Gross Area: 1,000,000 sqft
Year of Completion: 2024 (Phase 1), 2026 (Phase 2)