Is your apartment balcony really safe? The signs a collapse is coming

All of a sudden, the balcony begins to collapse. One man is killed and five others are injured when they plunge several metres to the ground from a seemingly safe-looking balcony.

This incident took place in August in the German city of Hamburg, but echoes similar accidents earlier this year in Texas, Turkey, Mallorca and Naples.

Everywhere local media print headlines about incidents like these, people often find themselves thinking: Should I be checking if my balcony is safe to stand on? And what even are the signs of an impending collapse?

First, the reassuring news is that accidents like these are relatively rare, according to engineering professor Norbert Gebbeken. But the less reassuring news, according to the structural safety specialist, is that it is often impossible for tenants and homeowners to tell if there is a clear risk of damage.

"With a balcony you can of course see whether algae is forming. This gives an indication of moisture that can also penetrate the building component," says Gebbeken. However, as balconies are almost always covered with tiles or another covering, it is very difficult to spot what is going on underneath.

Cracks can be seen better from below

As a rule, cracks in a balcony - the clearest of warning signals - tend to be seen from below, meaning by those people who live the next floor down and looking up from their own balcony.

"If a crack is visible in the widely used cantilevered reinforced concrete slabs, it's usually too late," says Gebbeken. In this case: Do not go out on the balcony. Either inform the landlord, or, if you are the owner, contact experts who specialise in structural damage.

"They have experience, know where to look, have moisture analysers and cameras that can be used to see into cavities," Gebbeken says. Incidentally, experts should also be consulted if individual parts of wooden balconies have become deformed or look a little crooked.

Be careful about what you store on a balcony

In general, however, prevention is always the best action, says Gebbeken, though owners of residential buildings are not always obliged to have their balconies checked without a specific reason. He advises having a balcony checked by experts once every decade.

"If you have balconies that are not only used by tenants, but are also part of a restaurant or such, then they should even be checked every three to five years," he adds.

If you live in an apartment, can also avoid accidents by making sure the balcony is not overloaded. Balconies in buildings made to modern standards are generally designed to hold 350 to 500 kilograms per square metre, he says.

"This means that four, five, six, seven people can easily stand on one square metre of balcony. They don't even fit on one square metre of balcony," says Gebbeken. "So the normal use of a balcony by people shouldn't be a problem."

However, things can be different if you set up a small paddling pool on the balcony, for example. "Then it becomes problematic because you then quickly exceed these loads," says the structural engineer.

The actual load-bearing capacity of a balcony can be seen from the building's structural analysis documents, which are usually available to homeowners.