Their residents pay rent to an enforcer who collects the money illegally. They do not have access to the most basic of services.
Just last week, the city of Johannesburg raided two buildings where the living conditions were described as deplorable.
According to a report on iAfrica, residents were paying rent for beds, not units, ranging from R250 to R1200 a person.
The city said it would find alternative accommodation for the former occupants of the raided buildings. It planned to redesign them into low-cost housing apartments.
With the living conditions that bad, one can only imagine the fire hazard buildings like this pose.
It is a complicated problem to solve. Joburg's mayor, Herman Mashaba, is on the record as saying he is trying to find a solution.
But until then, the reality is that hundreds of poor South Africans are left with no choice but to live in these death traps.
And that is the crime.