But ACT Fire and Rescue station officer Jeffrey Dau, a fire safety engineer, said a firewall was erected as an alternative.

Chief Coroner Lorraine Walker is presiding over an inquiry into the fire, which destroyed Flint, the Parlour Wine Bar, upstairs office space and damaged the Diamant Hotel.

Allianz Insurance brought in expert fire investigator Greg Kelly to find the cause of the blaze.

Mr Kelly concluded it most likely began in the Flint kitchen, in the exhaust ducting above the ceiling.

He told the court several access panels - meant to help cleaners reach into the ductwork - were not installed despite appearing on designs for the ductwork.

Earlier in the hearing Mr Dau said a firewall was installed in Flint as an alternative to an overhead sprinkler system.

Robert Clynes, counsel for Allianz, asked the witness if he believed sprinklers would have made the area safer. ''For the purposes of life safety and protection of other buildings the solution, in my view, achieved its purpose,'' Mr Dau said.

But, he added, ''for the purposes of property protection, such as a heritage building'', a sprinkler system might have provided additional protection.

Mr Dau said some elements of the exhaust ductwork were in breach of Australian building standards, but the Building Code of Australia did not presently enforce those standards.

The court has also heard a spray mechanism designed to cool timber and embers shooting out of the gas-and-wood fired oven was inactive at the time of the fire.

Fire investigator Anthony Walker earlier this week said he believed the device, if working properly, could have prevented the fire.

The hearing continues today.