The fire allegedly started in an exhaust duct system attached to the restaurant’s gas-and-wood-fired pizza oven.

The blaze gutted Flint, Parlour Wine Room and upstairs office space and damaged the adjacent Diamant Hotel.

An inquiry into the fire today heard installing ceiling sprinklers in the heritage-listed building was problematic.

But ACT Fire and Rescue fire safety engineer Jeffrey Dau told the ACT Coroner’s Court an “alternative building solution” was reached.

The alternative design plan involved the erection of a firewall bounding Flint and Bicicletta restaurants.

The court has also heard the flue system catered for two stove units as well as the pizza oven.

Mr Dau today said fluing the three devices together was a breach of an Australian standard, but one not enforced by the Building Code of Australia.

Likewise he said a lack of access ports for cleaning amounted to a standards breach, but again not one enforced by the code.

The inquiry has previously heard a fire safeguard in the oven, a spray device designed to cool rogue embers, was not active at the time of the fire.

And investigators found combustible material in the ductwork in the aftermath of the blaze, which could have contributed to the spread of the fire.

Fire investigator Anthony Walker also told the court the single-sheet thickness of the ductwork was unusual, and double- or triple-thickness was preferred.

But under questioning from Robert Clynes, counsel for Allianz Insurance, he acknowledged the oven manual described triple-sheet ducting as “highly recommended” but not mandatory.

The hearing before Chief Coroner Lorraine Walker continues.