First conceived in the weeks leading up to the birth of film-maker João Rosas’s first child, this documentary portrait of Lisbon was initially intended to be a memento between father and daughter. What began as a record of private memories, however, soon expanded and metamorphosed, as the film takes in the unsung labour that undergirds a rapidly changing urban landscape. Here is an elegy to a vanishing city, whose history is being erased, brick by brick.

Diaristic in form, Rosas’s camera takes in the day-to-day of a construction site; here nearly all of the workers are immigrants, mostly from Africa and South Asia. Once home to a printing workshop, the building is now being torn down to make way for luxury condos. Flourishing in the aftermath of the financial crisis and the tourist boom, the condo-isation of Lisbon purports to signal an economic rebirth. In reality, such development projects heavily rely on the maltreatment of marginalised workmen, who endure harsh conditions for little pay.

Rosas, who is also an author, brings a literary touch to his narration, which takes up the bulk of the film’s soundscape. His turns of phrase are frequently poetic, but also create a distancing effect between viewer and subject. We seldom, for example hear directly from the workers; their life stories are largely conveyed through Rosas’s retelling.

Furthermore, although well-intentioned and empathetic, the director’s observational approach neglects to situate the workers’ stories within larger social contexts. The specific hierarchy of labour depicted in the film might have resulted from the great recession of 2008, yet it is naive to perceive the exploitation of foreign labourers as a recent phenomenon. Considering Portugal’s colonial past, it would seem vital to observe that not only the “new” Lisbon, but the past eras of the city were built on the blood, sweat, and tears of the global south.

• Death of a City is at the ICA, London from 14 June.