Fire raced up 13 storeys of a Melbourne apartment building in part because the outside wall was not clad in fire-resistant sheeting, the city's Metropolitan Fire Brigade says in a report.

The fire, started by a cigarette on an eighth-floor balcony of the Charter Hall-developed Lacrosse apartment building last year, raced up to the 21st floor in as little as 10 minutes and stopped only because it reached the top of the building, the MFB report said.