A huge fire which began in the Japanese restaurant Coo had quickly destroyed large sections of the nearby businesses and covered the CBD in a smoke haze.

One year later, the damage from the fire can still be seen in the scaffolding which covers a large section of the Sydney Building.

Station officer John Wilson, who was among the first firefighters to arrive on the scene, said the main thing he remembered was the heat.

"We worked from the back of the building," he said.

"Visibility was zero, the heat was just intense, there was a mezzanine above us that partially collapsed.

"It just rained ash and the heat was so intense that we had to eventually pull out. It was very hard."

ACT Fire and Rescue commander Danny Brighenti said at one point the fire had taken all ACT resources except for a single fire truck.

"The old design had been renovated for there were walls which meant we couldn't get in to attack the fire directly," he said. "We didn't get water on it directly for several hours until the Bronto knocked down the roof."

Many business were affected by the blaze, including popular nightspots such as The Phoenix Pub and Shooters.

While some businesses have moved on and found new premises, some of those which have stayed are finding it hard to attract business with the ongoing construction.

Croissant D'Or manager Gina Carvalho said she remembered being scared on the morning of the fire.

"We didn't even notice, we were just working and then the police said 'get out, you don't have time'," she said.

"So we left everything behind.

"Customers say to me they don't go through here because there's nothing to go through," she said. "It's hard, it's been very quiet and someone has told me [construction] might be another eight months. It's not very good for business."

Salsabor Dance Studio was on the second level of the Sydney Building before the fire, but was forced to relocate due to the extent of the damage.

Co-owner Andrea Paez-Warner recalled the shock of going back to the office after the fire.

"[It] was completely devastating because you put your heart and soul into it," she said.

"All of our trophies were melted and most of our stock was destroyed. It was a sad day."

One year on, Ms Paez-Warner said they had more classes than before at their new premises in City Walk, a couple of which are even sold out.

"We had a lot of vision to see it becoming a great facility for us to keep doing our classes so we did it ourselves," she said.

"A lot of time was spent getting it up and running again ... [but] we have 30 classes running a week now ... we're over the moon."

Work to restore the outside of the Sydney Building began in November and is set to be completed next month.