Katajanokka Pier

Katajanokan Laituri (Katajanokka Pier) is a solid wood office building that is now part of Helsinki’s historic seaside. With the completion of this first new building on Katajanokka’s waterfront, the previously closed-off harbour area is gradually opening up for Helsinki residents and visitors. The building design stems from an invitation-only international architecture competition arranged in 2020.

Read the article in Finnish here.

The building both supplements Helsinki’s distinctive silhouette and long coastline and adds its own layer to the historically diverse buildings on Katajanokka. The project aimed to look peaceful when viewed from
afar while providing interesting experiences to those walking by: the shape appears to change as the viewer changes perspective. The entire experience also had to fit in with the varying scales and motifs of Katajanokka. Set amidst the elongated structures of the port area warehouses, the building is split into sections by free-form recesses in its façade. These recesses also create sheltered alcoves for the outdoor spaces and provide carefully considered views from the interior to its surroundings.

Katajanokka Pier aims to show the way to a future where modern wood is used as part of sustainable urban construction. From its inception, the project was guided by the goal of minimising climate impacts during its entire life cycle by extending its service life as far as possible, enabling conversions and a diverse range of uses, and being low carbon and energy efficient. Thanks to its structural system and interior dimensions, the inside of the building can be modified as needs change.

The building has four floors above ground and a communal roof-top terrace. Technical facilities and parking are in the subterranean basement. The ground floor hosts services that complement the surrounding urban spaces, such as a restaurant, a café, and event facilities. The various occupants, visitors, and city residents come together in the shared lobby that leads from the street to the sea.

Above-ground, Stora Enso’s prefabricated solid wood structures are the primary construction material. The pillar-beam frame and the façade’s load-bearing structure are made from LVL manufactured at the company’s factory in Varkaus, Finland. CLT from the Gruvön Mill in Sweden was used for the interior walls, elevator shafts, stairwells, stairs, intermediate floors, and top floor, which all serve as load-bearing and stiffening structures in the building. Altogether about 7,600 cubic metres of spruce went into the building frame – a total of 2,500 wooden elements. Structural wood has been left visible in the interiors to the
greatest extent possible.

The façade extends the light-coloured row of buildings running from the Esplanade, continuing their horizontal, regular rhythm. The prominent location was demanding both visually and technically, leading to a solution that uses a double façade structure. The outer protective layer echoes the materials in the surrounding stone buildings by using a combination of glass, natural stone, and aluminium. Its look changes over the course of the day and with different lighting conditions.

Meanwhile, wood in its many forms is tucked behind the façade. The most recognizable features of the interior public spaces are the shaped, solid LVL pillars on the ground floor and the sculpted CLT clad skylight in the central lobby. Ash is used alongside spruce in the surfaces and cladding, and their colouring was kept as natural as possible to highlight the wide-ranging beauty, tones, and usability of wood. The general approach was to use low-emission and natural materials as they age beautifully with their natural patina. Light-coloured granite from Viitasaari covers the lobby floor and continues outdoors. The lobby furniture leverages Finnish design and artisanry, and the office spaces make use of recycled and reused furniture.

Our northern nature provided the inspiration for the exterior spaces of the building. The terraces and courtyard each represent a different habitat and its related vegetation. A birch tree grows in the narrow courtyard, with its canopy sheltering the different plants around it, and the terraces on the first floor have the vegetation and natural stones typical of the rocky Finnish archipelago. The roof is covered with a meadow rippling in the breeze. The vegetation forms colour themes that change over the seasons,
and the meadow-like roof also has a serving area, lounges, fitness areas, and solar panels. The various exterior spaces create a small natural island refuge in the middle of the city, where humans and our urban animal friends can thrive.

Due to the site’s location on the shoreline, the team chose to construct flood protection pre-emptively. The entire South Harbour area will undergo a similar process later to combat the increasing risk of flooding. The City of Helsinki has plans to transform the Katajanokka shoreline into a pedestrian zone with a walkway from Kauppatori Square to the end of Katajanokka. As Katajanokka Pier lies along this path, the city will soon build temporary structures around it at street level.

Technical solutions

The building is in fire class P2 and equipped with a fire detector and automatic extinguishing equipment. Because of its size, the building is divided into two parts by a wooden structure much like a fire wall. Fire simulations were used to verify the safety of the solid wooden slats in the central lobby.

To meet the LEED Platinum level environmental certification requirements, the building acoustics were designed for a higher quality level than usual. The result is a building with superior work environments, pleasant public spaces, and comfortable hotel rooms. Thanks to the acoustic solutions, it was possible to place hotel rooms above the gym, office spaces above the conference and restaurant facilities, etc.

The noise from ships in the Katajanokka Harbour, and the South Harbour nearby, placed exceptional demands on the façade’s sound insulation. This was another reason to opt for the double façade solution: the combination of the exterior glass, the inner façade, and the air in between them was optimised to combat the low frequency noise typically produced by ships. The building interiors remain quiet despite the noisy ships docking at the adjacent pier.

Indoors, the LVL column-beam frame and its simple fixed joints were soundproofed with sound insulation panels and raised floors. The sound insulation design provides superior acoustics while meeting the location’s architectural goals and retaining visible wooden structures.

The structural engineering was guided by the building’s ambitious architecture and seaside location: the wooden frame rests on a watertight, concreted basement built on piles and is made from LVL pillars and beams with CLT stiffening slabs and walls. The site has unique structural solutions, including an inverted roof on a wooden ceiling structure, a wooden firewall solution, and a wooden-framed prefabricated façade system developed specifically for the site. These prefabricated elements with double-glazed glass protect the wooden frame from weathering and keep the temperature indoors comfortable for the people inside. Airflow through the 40 cm wide space is monitored constantly with sensors to ensure
success.

The construction project

Katajanokka Pier was developed by Varma under a project management service model. Haahtela oversaw project and site management, handling the roughly 70 subcontractors on site. Stora Enso is the anchor tenant, with the hotel operator Sokotel joining at an early stage. Based on the architecture competition
in 2020, a zoning plan change was prepared for the area.

An old harbour building was demolished to make room for the new complex. Demolition began in August 2021, continuing with earthworks in December 2021. Work on the bove-ground frame began in March 2023, and its installation was completed in early October 2023. The elements were installed directly off delivery trucks without intermediate storage. The delivery and installation dates were agreed six months before work on the frame even started, and in the end, were correct with an accuracy of two days. The wooden elements were manufactured at Stora Enso’s factories without traditional “label images”, instead using a 3D model created in cooperation with the company. Handover took place in stages: the office to Stora Enso at the end of June 2024 and the hotel to its tenant in mid-August 2024. The hotel welcomed guests on August 26th, 2024.

Key lessons from the process:

• The extremely small installation tolerances of the pillar-beam frame joints were the biggest challenge during the wooden frame’s installation. The small tolerances were partly due to the stiffening structures also being wood.
• Drilling holes in LVL elements retroactively may prove even more challenging than in concrete structures.
• Employees find the wooden frame itself quite pleasant: it is silent, dust-free, and bright (compared to concrete).

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