The ACT Industrial Court heard miscommunication between workers prompted an excavator driver to smash his bucket into the roof of the Torrens home, sending a plume of dust into the air, before workers had started to spray it with water.

But Industrial Magistrate Lorraine Walker said on Tuesday there had, "fortuitously", been no asbestos contamination as a result of the demolition despite initial fears workers, including a WorkSafe ACT inspector, had been exposed to deadly fibres.

Samarkos Earthmoving pleaded guilty to failing to comply with its duty under workplace health and safety laws for failing to ensure adequate water suppression and effective communication between workers and machinery operators at the property.

The company was principal contractor at the private demolition of the Darke Street home on August 20 in 2015.

It had experience in dealing with asbestos, enlisted the help of asbestos removal specialists and had prepared numerous safety plans before the August 20 demolition, which WorkSafe attended.

Workers had also discussed safety measures, including dust suppression, during a "toolbox talk" soon before the demolition began. The court heard workers said the house had previously been sprayed with water and was already damp on the day.

The excavator had been in place when a ground worker asked the operator, "Righto ... are you alright to go?", to which he had replied, "yep".

The court heard the driver mistakenly believed that exchange meant he could start to demolish the house immediately, rather than begin once workers had started spraying water on the house.

"This was a clear miscommunication," Ms Walker said.

The driver dropped the excavator bucket into the roof of the house, causing a cloud of dust to emerge from the building.

Workers on the site yelled at the operator to stop as the radio inside the machine was not working and there was no air horn available, despite advice the previous day there should be one on site.

They eventually spoke to him on his mobile phone and he stopped the machine, but only after two people on the site had climbed under the site's safety barricade as they tried to get his attention.

The workers immediately decontaminated themselves.

Ms Walker noted work on the site had started again that afternoon and said: "Despite earlier concerns, no contamination from this breach has been established."

But Ms Walker said she needed to take into account the overall risks that could stem from the company's behaviour, noting the potentially deadly dangers of asbestos and the number of people in the vicinity of the demolition.

"The risk to members of the public, as well as to workers on the site, was significant."

Ms Walker accepted the company had generally acted responsibly in enlisting the asbestos removal business and preparing the required safety plans, but said its approach to implementing those precautions "ultimately rendered them ineffective".

She noted there was only one water hose at the site, instead of two as required, and said the lack of effective communication channels between workers was "a significant breach".

Ms Walker rejected the defence team's argument the breach was minor and caused partly by an "over-exuberant employee" as opposed to a "preventable or predictable systems failure".

She noted the company's cooperation with the court case, its otherwise good character and lack of prior offending.

Ms Walker said the incident before the court wasn't trivial, but considered it less than mid-range seriousness for offences of its type.

She recorded a conviction and gave the company six months to pay the fine.

Access Canberra acting deputy director-general David Snowden welcomed the court's decision and said in a statement it sent a "clear message" to the construction sector that "dangerous and unsafe work practices" were not accepted.