Grand Hansa Hotel is a major renovation project which transforms three historical investment properties in the central business district of Helsinki – New Student House, Hansa House and Hotel Seurahuone – into a high-standard hotel at Kaivopiha opposite the main railway station. The new complex extends over nearly the entire block via a new cross tunnel. Built in the beginning of the 20th century, these properties are all listed for preservation, and the project includes improvements and partial renovation of their foundations, structures and building services systems. The Hansa House will have three new floors and a restaurant located in its listed cupola. The new hotel will have 224 rooms, a garden conservatory, and event and meeting rooms, including a two-storey terraced restaurant. Structural design for the project is provided by AINS Group’s A-Insinöörit Suunnittelu Oy.
The project kicked off with some demolition work in January 2021, and the hotel is to be completed in 2023. Sustainable development is taken into consideration in all project phases, and the complex will apply for a LEED® Gold level environmental certificate. The carbon footprint of the project is being reduced throughout the project, in terms of procurement, construction and in-use environmental impact. Sustainability and quality will steer the hotel’s interior design, too. The Grand Hansa will be a unique 5-star luxury hotel and the first member of the Unbound Collection by Hyatt chain in the Nordic countries.
The old properties are renovated to meet modern hotel standards while honoring their heritage. In accordance with the Finnish Heritage Agency’s highest preservation category SR1, the facades and the wall and ceiling surfaces will be preserved, and, for example, some of the old wooden beams in the cupola must be preserved. The entrance hall lobby is restored to comply with the original design. The properties’ floor heights vary from 2 to 5 meters, and inside the building as well as relative to the adjacent buildings, all floors have different elevations. The project involves very distinctive structures, which is why its structural design is demanding. About 60 percent of the measurements were missing. However, all necessary sections of the building were modeled, which resulted in a very exceptional structural model.
Modeling a renovation site is challenging compared to new build, yet absolutely necessary
Challenges in the project include lack of initial data and fitting modern building services technology among old structures. Many measurements taken on location and investigation of the load-bearing structures including demolition were needed to form a basis for the design. However, it was possible to use point clouds as initial data, and the structures measured “as built” in the model and reviewed against old drawings were color coded. It was challenging to fit in new building services systems because of fairly thin intermediate floors containing old steel and concrete beams that cannot be broken. There was a risk that modern components, such as drain pipes and floor drains, clash with the load-bearing structures. Steel structures were installed on site, however, and converting natural ventilation to a mechanical system required constructing new shafts through the building while using Delta beams, for example. Building acoustics were improved by adding intermediate floors and acoustic profiles.
Tekla Structures was used for the structural design of the project. Modeling helped considerably in connecting new and old structures that are tilted and skewed in many directions. It would have been completely impossible to perceive the existing geometry in 2D, with all floors at different elevations and the unique, multidimensional structures. The cupola and its structures are so complex that it is not possible to understand their geometry from the drawings alone. New and preserved old structures are easier to understand in the Tekla model. In addition to modeling, drone photography was used to help perceive roofing structures.
In addition to adding attribute data, old and new structures were categorized in the model by using color coding. This made it easier to focus on the most important structures during the design. Thanks to Tekla Model Sharing, the structural steel fabricators were able to utilize structural design information in real time. The building component provider of the raised section Teräsnyrkki designs and models their steel structures, and Peikko designs the new elevator and ventilation shaft’s Delta beams directly into the Tekla model created by AINS. In addition, the provider of the glass facades designs by modeling using the structural IFC model as reference, and their model is imported as reference to the Tekla model. The model is more than 100 m in diameter, containing circa 1,300 modeled wood assemblies, more than 7,500 concrete assemblies, circa 4,400 steel assemblies, and more than 1,000 renovation-related drawings.
Structural design: A-Insinöörit Suunnittelu Oy
SPR- design: Sweco Talotekniikka Oy
Owner: Ylva Palvelut Oy
Contractee & BIM coordination: Sweco PM Oy
Operator: Primehotels Oy
Project Management Contractor: Skanska Talonrakennus Oy
Principal design & Architect: Arkkitehdit Soini & Horto Oy
Interior design: Sisustusarkkitehtitoimisto Carola Rytsölä Oy
HVAC design: Insinööritoimisto Leo Maaskola Oy
Electrical design: Rejlers Finland Oy
Delta beam parts supplier: Peikko Finland Oy
Glass facade supplier: Metek Oy
Steel structure parts supplier: Teräsnyrkki Steel Oy