Jamie Lee Morrison and Chloe Arnott started the blaze within a top-floor flat on Francis Street, Lochgelly, on October 23, 2023.
The building – which was home to twelve people – was demolished in December 2023 due to the damage caused.
The rebuilding costs faced by Fife Council are approximately £2.1 million.
The fire was started in the bedroom of a flat belonging to the ex-partner of 31-year-old Arnott.
A piece of paper was set alight using a cigarette lighter before the couple left the building without attempting to alert the block occupants.
Eight residents were later evacuated after a neighbour heard a ‘loud crackling noise’ coming from the adjoined flat.
He touched the wall of his living room, which was ‘very hot’.
The neighbour ran out of his flat in a panic and could see orange flames through the glass panel of the nearby flat’s door. The glass was starting to shatter.
He ran downstairs, knocking on the doors of all the flats on the way down and telling the occupiers to get out. No one was hurt during the incident.
The fire service sent five appliances to the scene and worked throughout the night to extinguish the flames.
After leaving the block of flats, Morrison, 34, admitted to a friend that he had set paper alight and the flat had gone on fire, which he said he did not intend to do.
On July 25, 2024, at the High Court in Edinburgh, the couple admitted a charge of wilful fire-raising to danger of life.
On September 5, at the High Court in Stirling, Morrison was jailed for 64 months and Arnott for 52 months.
She was also made subject to an eight-year non-harassment order.
Moira Orr, who leads on homicide and major crime for the Crown Office and Procurator Fiscal Service, said:
“This was an extremely reckless act that could have had devastating consequences had it not been for the swift actions of a neighbour.
“Instead of alerting residents to the fire taking hold, Morrison and Arnott simply left the property without raising the alarm.
“They will now have to face the consequences of their dangerous actions, and I hope this conviction brings some comfort to those affected by their offending.
“Our prosecutors will continue to do our utmost to prosecute those who carry out dangerous acts such as this to help keep the communities we serve safe.”