Under

This is how the underwater restaurant will be built

Published on January 18th, 2018

The construction will be built on a barge, and when finished, it will be lowered into the sea and attached to foundations on the seabed. That´s when the interior work can begin.

- Under will be the world´s largest underwater restaurant, describes Arne Marthinsen.

He is project manager in SubMar Group, an interdisciplinary group of companies, responsible for the wave calculations and the marine operations in the project.   He and his peers have dimensioned and planned the construction, the shipping and the subsea installation, as well as calculated what the construction must be able to withstand from the fierce natural forces.

According to Marthinsen, it isn´t the underwater building it self which is the most extraordinary about this project, that has been done since the 1970s in Norway.

- What makes it so complicated and unique, is the fact that it isn´t going to be a simple, concrete storage tank, but rather an amazing, unique experience for people due to the location, the architecture, the interior, the underwater view and the gourmet food.

Formed as a pipe
The underwater restaurant, designed by the architectural bureau Snøhetta, will look like a thick, rectangular pipe made out of rough concrete. One end rests on the shore, while the remaining part of the pipe slopes down below the surface, landing on the seabed approximately six meters below the sea level.

- The harsh and rough conditions we have in Lindesnes have made it necessary to pay additional attention to the construction it self and the materials used when building it. The construction must be able to withstand enormous natural forces from both the sea, the waves, the weather and the wind, he explains.

Therefore, when designing the construction, it was crucial not to design a geometric shape that would challenge the rolling of the waves, but rather live with them.

- And in collaboration with other academic communities, we have scrutinized weather data from the area, as well as taken into account a scenario of a thousand-year wave. After considering these and a number of other factors, Asplan Viak has found that the walls of the outer structure should be 0,5 meters thick and consist of reinforced concrete.

The 11 meter long and 3,5 meter tall panoramic window, which will give the guests a fantastic view of the subsea life, is of course also produced to withstand the fierce underwater conditions and pressure.

After having verified all the calculations, Marthinsen can guarantee the absolute safety of the construction.

- Should a thousand-year wave occur, you will be completely safe within the restaurant, he says.

Built on a barge
January 15, 2018 marked the start of the construction of Under.  

BRG is responsible for the building of the restaurant-construction, and the work is carried out on a barge anchored up close to the place where the restaurant will be launched into the sea in July 2018.

- The entire pipe structure will weigh between 1500 and 2000 ton when finished, says Marthinsen, illustrating the weight by comparing it to cars.

- If an average car weighs 1 ton, you will need around 1500 cars to amount the same weight.

When launched into the sea, the structure will be attached to steel rods glued into drilled holes in the ground.

- This operation is what I consider to be the most challenging part of the project. We have exact calculations which tell us where and how to lower the construction into the sea, but I must admit I will be relieved when the work is done.

Once it has been done, the interior construction work begins. The work also includes making state-of-the-art solutions for power, ventilation, water and sewage. When finished, the restaurant will consist of three levels; the entrance section at the top, the mezzanine in the middle, and the kitchen and restaurant on the lower level.

- The interior will have a dark wooden finish, which will work as a contrast to the rough concrete, says Gaute Ubostad, initiator and co-owner of Under.

- And in March 2019, the restaurant will open up to the first guests. We are really looking forward to it.

ABOUT THE CONSTRUCTION:

  • Weight: 1500-2000 ton
  • Bottom surface:  Length 26,5 m, width 12,5 m Exterior walls: Thickness O,5 m, reinforced concrete
  • Window: Thickness 0,32 m, width 11 m, height 3,5 m Mezzanine: 139 square meters
  • Restaurant 265 square meters
metres below sea level