The vice president of the College of Industrial Technical Engineers of Valencia and specialist who examined the 14-story building in the Campanar neighbourhood, Esther Puchades, has attributed the spread and severity of the fire to the type of cladding used on the outside.

According to the expert, the cladding was made from polyurethane, which is a versatile plastic material, which exists in various forms. It is used in everything from shoe soles to sportswear fabrics and mattresses.

It’s also often found in building construction, particularly for cladding and insulation.

The material is highly flammable, and Puchades has explained that “when heated, it catches fire”. 

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The use of polyurethane in the construction of buildings in Spain was common during the 2000s and 2010s and it is not currently known exactly how many buildings in the country have polyurethane cladding.

The building where the Valencia fire took place was constructed in 2005 and completed in 2009, a time when the risks and dangers of polyurethane were not widely known, explained the expert. 

Professor Antonio Hospitaler who investigated a similar fire that occurred in the Windsor Tower in Madrid in 2005, explained that the spread of the fire when polyurethane is used is “much faster than an open-air fire” and would not have been such if the building had been built with brick.

Polyurethane cladding has also been attributed to the severity of other recent fires, namely the Grenfell Tower fire in London in 2017.

Since 2006, the Technical Building Code states that materials used on the façade of a building must not be combustible in order to avoid the spread of fire, however, the use of polyurethane in building construction in general is not illegal in Spain. 

“Today it is [Polyurethane] is not used, at least not in that way,” Puchades explained in a Valencian public television À Punt.

When asked if she knows if there are other buildings in the city built with similar materials, Puchades admitted that she doesn’t know, but claims that it is highly possible and highlighted the need to investigate further “for the safety of the people”.

She explained that currently the use of polyurethane is not prohibited in construction in Spain, but given the voracity of the Valencia fire, the use of the material could be reconsidered. 

The fire that ripped through a 14-storey apartment block in the city on Thursday evening has left at least four people dead, but officials say that 19 people are still unaccounted for.