The fire destroyed the heritage-listed building that housed office space and popular eateries Flint restaurant and Parlour Wine Room.

Bicicletta restaurant and the Diamant Hotel were also damaged.

Chief Coroner Lorraine Walker handed down her findings on the June 23 fire in the ACT Coroner's Court on Friday. The Coroner found the fire was accidental and started in the exhaust ductwork attached to Flint's pizza oven.

She said the fire started when combustible material in ducts above the restaurant was ignited by heat or embers from the woodfire oven.

The court heard that a lack of cleaning access panels in the ducts led to a build-up of the combustible material, and a spray filter designed to cool hot embers was inactive at the time of the fire.

Ms Walker made three recommendations, including that certification processes needed to be clearer.

She said contracts for work to be undertaken needed to be more clearly defined in formal documentation between subcontractors and project managers.

Third, she said all hospitality staff should be required to sign an agreement that they have read the instruction manual before being granted permission to operate commercial cooking equipment.

During the November hearing, the court was told the subcontractor hired to install the ducts was an experienced air-conditioning installer but had little experience handling commercial kitchen ducts.

The Coroner was told that some elements of the exhaust ducts breached Australian building standards.