San Francisco Frontiers - Why did a Dominican nightclub roof cave in?

Experts, meanwhile, said the causes appear to be clear: insufficient support for too heavy a structure also weakened by a fire almost two years ago.

Video footage of the last moments before the roof of the Jet Set club came crashing down in the wee hours of Tuesday showed people leaving the venue in a rain of dust from above.

Survivor Iris Pena told local television she made for the door after dirt started falling into her drink and a stone fell and cracked the table she had been sitting at.

Another video showed the stage with merengue performer Rubby Perez singing to an adoring crowd as someone comments that a piece of slab had fallen down.

The videos end in darkness, crashing sounds and screams.

- Overloaded? -

The Jet Set nightclub was 52 years old, and operated in a building originally constructed to house a cinema.

Standing two floors high, with walls painted black, it featured a large hall with a spacious dance floor adorned with disco balls, large, heavy speakers and light fixtures.

It could host 700 people seated at tables, and 1,000 standing.

An aerial view of the disaster site shows air conditioning machines and power generators weighing tons lying among the roof rubble.

"Imagine you put two or three 42.5-kilogram (93.7-pound) cement bags on your head... your feet are not going to hold," explained Persio Diaz, a civil engineering professor at the Autonomous University of Santo Domingo, adding: "the supports were not sufficient to withstand the loads."

He added: "If you overload a structure, it will not support you."

Architect Garivalddy De Aza analyzed photos of the roof slab on Instagram, and observed "not a single column to relieve the load" of the structure.

"The roof collapsed under its own weight," he concluded.

- Fire damage? -

In 2023, a fire broke out at the nightclub after lighting struck. Firefighters who put out the blaze said at the time the building's integrity had not been compromised.

But Diaz said that "when a structure like that is affected by a severe fire, the durability of the concrete... deteriorates significantly" and it "turns into a kind of weak concrete."

He also pointed out that steel corrodes with time, and the high humidity in the Caribbean country can affect the soundness of building materials over time.

De Aza said there appeared to have been "a lack of planning in the building's growth."

Juan Villar Gonzalez, a former president of the Dominican College of Engineers, Architects and Surveyors, said the building also lacked circulation and emergency doors.

"There has been little supervision," noted Villar, adding the tragedy needed to be studied in detail and lessons learnt to prevent another in future.

The Jet Set said Tuesday it was working "fully and transparently" with authorities investigating the calamity.

T.Martin--SFF