Skanska has been assigned to renovate and refurbish Nationalmuseum in Stockholm. Skanska is the general contractor, in collaboration with the National Property Board of Sweden. Renovation of the main building includes new visitor facilities, raising the floor in the atriums, lowering the floor in the basement, new windows, the installation of elevators, and replacing all electrical installations. We will also upgrade the museum park and build a loading facility.
Careful construction process
The project commenced in August 2014. We covered the sections that require protection and performed other preparatory work. It is essential that we protect this historic building from water, vibration, dust, subsidence and other elements of the construction process. This was followed by earthworks and foundation construction for the new loading facility.
“Since this is a waterfront site, we installed retaining walls and then excavated until we reached the groundwater table. Then we lowered the water table inside the walls to avoid having to excavate wet loads. At the same time, we sawed off 12 meters of the Annexe to make room for the loading facility,” says Pontus Lindeberg, Project Engineer.
The concrete structure in one of the atriums has been demolished to restore it to its original condition and allow the light back in again. The boarded-up windows in the main building will be reopened and replaced with more modern versions.
Better climate for collections and visitors
Modern demands on the indoor climate in museums are high. Preservation of the collections requires ideal temperatures and relative humidity. These levels are controlled by a system that is sensitive to variations caused by weather conditions and the number of visitors. We are working silently in the background to replace all installations in the building and significantly extend the climate-control system.
The Swedish National Heritage Board has set demanding requirements for how this should be implemented, which affect us in terms of the methods we choose, financial constraints and time. During the design stage, several special solutions were created that conceal the technology in smart ways.
The new and modern climate-control system can measure relative humidity and room temperatures, and maintain ideal levels. Skanska delivers a total solution. Fredrik Johansson, Project Manager, describes the challenges posed by the installation of a climate-control system:
“We are not permitted to change the layout of any of the rooms, and the size of shafts is highly restricted. Concealing so many space-consuming installations is not easy. We are reusing all vertical shafts. We are also installing a new duct system underneath the floors. This involves lifting the flooring, installing ducts and relaying the flooring.
Air will flow into the rooms through custom-made ceiling medallions in the beautiful domed ceilings. These medallions will also serve as ceiling sprinklers, thereby concealing two practical features in one beautiful detail. Such smart solutions will provide Nationalmuseum with an indoor climate that is ideal for both collections and visitors.
Basement dug out
The floors in the atriums will be raised to improve accessibility at entry level. At the same time, the floor will be lowered in the basement, which was previously no more than standing height. New visitor facilities will be created in this area, including toilets, wardrobes, stroller parking and a picnic room. We will also build several new ventilation and electrical equipment rooms, as well as a large kitchen on this level.
Since the entire building stands upon rock, the project requires rock and soil excavation under the building. We are blasting very gently to prevent subsidence.
Nationalmuseum is a unique project in many ways. According to Fredrik Johansson,
“The chance to refurbish a property of this caliber only comes along once in a lifetime. The project group is very committed, and we all have great respect for the building. We also enlisted the services of an antiquarian expert. Respect for the building means that we are working even more intensively than usual to prepare each stage.”
Project in figures
- 5,300 cubic meters for added installations, equivalent to 52 city buses.
- 2,300 square meters for expanded visitor facilities, almost as much as 12 tennis courts.
- 300 windows will be renovated. Some inner windows weigh 800 kg.
- 22 white-collar workers are involved in the project. A maximum of about 200 skilled workers will be on site.
- 75 meters – the depth by which the floors will be lowered in the atriums.