It comes despite all other states and territories signing up to the 2019 Building Code of Australia on May 1.

The decision has come as a surprise to the ACT's peak building group, which wasn't made aware of the delay until the day before the updated code was due to be adopted.

Minister for Building Quality Improvement Gordon Ramsay on Monday signed off on a measure allowing the ACT to delay the adoption of the code until September 1, 2019.

The national construction code sets out minimum standards for buildings, including design, fire safety, accessibility, health and energy efficiency.

The codes have historically been updated annually, with an "assumed" adoption date of May 1 each year.

However, it has been three years since the last update after state and territory building ministers agreed in 2014-15 to move away from annual refreshes. Governments are not required to adopt the code by a particular date.

A preview of the 2019 update was released in February, before an online version was published on March 25.

The 2019 code, which spans about 2500 pages, includes new requirements for fire sprinklers in apartment buildings four storeys and above, revised energy efficient targets for commercial blocks and added provisions for condensation management.

A statement explaining Mr Ramsay's decision stated that the "short period" between the preview's release and the slated May 1 adoption date had not given owners and practitioners enough time to tweak designs for planned projects to ensure they met the new rules.

The statement said the update included "substantial changes" to the code, including to "increase the stringency of some standards".

"It does not provide a practicable transition for projects for which an application for a development approval has been made but not determined, or for a development approval that has been granted but there is no building approval," the statement read.

"To allow people to familiarise themselves with the new requirements and make any necessary changes to projects in the planning and design phase, this instrument amends the adoption date for the ACT to 1 September 2019."

Mr Ramsay did not directly address which changes the statement was referring to when contacted by The Canberra Times.

He said many jurisdictions had different approaches to adopting the code, noting Western Australia used a 12-month transitional period to usher in the changes.

He said the government had considered industry feedback before deciding on the delay.

Master Builders Association of the ACT chief executive Michael Hopkins said he first learned of the government's decision to delay the adoption of the new rules on April 30, a day before they were expected to come into effect.

The Australia Institute of Building Surveyors ACT branch also emailed members on April 30 stating that it had just been advised of the government's move.

Mr Hopkins said the association had held workshops with members to help them prepare for the code's May 1 introduction. He was not opposed to the delay, saying it would allow for extra time to adjust to the changes.

But he was critical of the government's lack of communication, particularly given the widespread concerns about problems in the ACT's construction sector.

The ACT government has faced constant criticism over its handling of issues plaguing Canberra's construction boom, which have been laid bare in an ongoing assembly inquiry.

On Wednesday, the inquiry heard claims that Access Canberra's lax approach to enforcement was "emboldening" builders and contractors to cut corners and deliver substandard work.

"With building quality being such a high-profile issue at the moment, I think that it's important that the government works closely and communicates with industry," Mr Hopkins said.