Ensuring fire safety at world’s tallest timber building Mjøstårnet

Mjøstårnet in Norway will be the world’s tallest timber building when it is completed in 2019 and fire safety has been very much at heart of the build. Timber Construction takes a closer look at the measures that have been put in place.

The 18-storey Mjøstårnet tower in Brumunddal will stand at 81 metres (over 265 feet) when it is complete.

Groundwork started in April 2017 and construction of the glulam structure in September of the same year. The building is being assembled four storeys at a time, during five construction stages.

Designed Voll Arkitekter AS for AB invest AS, Hent AS is turnkey contractor and Moelven Limtre AS is turnkey subcontractor, supplying supply glulam columns, beams and diagonals, CLT elevator shafts and stairs, and Trä8 floor slabs for the tower building and swimming hall

Up until 1997 it was prohibited to build timber houses taller than three storeys in Norway, due to the old “brick law,” which came into effect after the Ålesund city fire in 1904 but much has changed since then said Rune Abrahamsen CEO of Moelven Limtre.

“At Moelven we have long experience building tall and fireproof timber buildings,” he said. “The key is in the structure and the use of glulam beams.”

The building has been designed to withstand a burnout fire which means a fire that is allowed to develop freely without active extinguishing. It is the same concept as when you place a huge log in the fireplace. It won’t keep burning unless replenished with kindling and while the log will quickly develop a layer of charcoal, the fire will die out by itself.

“The fire safety measures that have been implemented in Mjøstårnet make the timber building far safer than a corresponding building with a traditional steel and concrete structure. Mjøstårnet is one of the safest buildings along lake Mjøsa, and can withstand even an extensive fire,” said Even Andersen, fire consultant with Sweco Norge AS, the company responsible for fire safety in the building.

In addition to Mjøstårnet being designed to withstand a burnout fire, a number of additional measures have been implemented. For example, the façade is protected against fire spreading, the building has an upscaled sprinkler system, and each individual room on each floor is designed as an individual fire cell to prevent fire from easily spreading to the next room.

For more information on the fire safety measures at Mjøstårnet watch this film –

Six fireproof measures in place at Mjøstårnet:

The glulam structures: The glulam structures have such huge dimensions that they retain their load-bearing ability in the event of a burnout fire and are positioned so that they won’t affect each other in the event of a fire.

Sprinkler system: A state-of-the-art sprinkler system covers the building inside and out. It differs from a traditional sprinkler system in that it is scaled to provide a greater water volume and has an independent extra water supply, as well as a greater degree of monitoring.

Facilitation for the fire brigade: Dedicated control room with graphical overview that enables fast and efficient extinguishing. The fire alarm is linked directly to the fire brigade, and the fire brigade’s water supply is doubled.

Fire strips: The weakest point in a timber structure in the event of fire is the steel used for the actual connections in the structure. The glulam structure therefore has fire strips to protect the steel sheets and dowels in the junctions and joints. The fire strips consist of a material that expands 20 times at 150 degrees Celsius. The strips protect the steel from the increase in temperature, close openings and prevent fire from spreading.

Fire cells: Each individual floor, apartment, and each hotel room are designed as separate fire cells that will restrict fire from spreading.

Protection against fire spreading in the façade: The outer wall elements have been treated with a fire-retardant material, and cavities in the façade are broken on each floor.

IMAGES – Jens Haugen/Anti


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