- Flame Retardants
On 20 May 2008, a spectacular blaze destroyed one third - around 1 600 square meters - of the Berliner Philharmonic roof. Although the first fire engines arrived at the scene just six minutes after the alarm was sounded, fighting the fire proved difficult. The firefighters had to cut a hole in the zinc sheeted, tent-shaped roof some 50 meters above ground to get to the fire and extinguish embers and glowing parts in the roof structure over the concrete ceiling of the concert hall. Copious amounts of smoke developed up to 500 meters around the fire site. The concert hall underneath and the precious instruments were not damaged. Nobody was hurt.
Initially is was not clear how the fire started. One week after the blaze, the investigations on the fire cause were completed. It had now become evident that the fire was caused by welding work. Repairs had been done on the roof of the Philharmonic, and parts of the zinc roof were removed to exchange defective roof sheeting. According to the police, a burner was used and obviously, the insulation structure under the roofing ignited, leading to a smouldering fire.
The roof structure consists of:
Basis: Concrete roof
Next layer: bituminous sealing
Next layer: wood structure with mineral wool in between
Next layer: wood planking
Next layer: bitumen roofing sheet
On top: Zinc sheeting
This fire has shown that even roofs insulated with non-combustible insulation materials like mineral wool may contribute to blazes with strong smoke development. The reason is that insulation materials are not used alone but in conjunction with combustible materials like wood and bitumen. The non-combustible mineral wool may lead to smouldering fires and promote the formation of embers difficult to fire fight.