The nation's top spy says he has been presented with a range of reasons for the long delay.
Under questioning by Liberal Senator Zed Seselja in Senate Estimates, Mr Irvine said the automatic doors required a significant makeover and there had been problems with the chilling and cooling systems.
The ASIO director-general said the size and compartmented nature of the expensive new building had been a problem.
"That has then had an impact on the air conditioning and air pressure throughout the building, which in turn has an impact on fire, if there is a fire in the building.
"It has taken considerable time to work that out," he said.
"We are assured all [of] those matters will be addressed, or are being addressed, and we are proceeding now on the basis the end of next month will be for us the practical period where we can begin our work."
Remediation work on the building's air conditioning and fire control systems may still hold up the spy agency's plans.
Mr Irvine said ASIO has been given money for current rent and is not paying rent on the new building until it is occupied.
"In that sense the costs are neutral. Where the costs come is in the delay combining your staff into one building and all of the efficiencies that that provides," he said.
The ASIO building will eventually house the Australian Cyber Security Centre and will be dedicated to countering new threats.
