A NSW upper house inquiry into the regulation of building standards, quality and disputes sat on Tuesday for the third and final day after a spate of incidents involving damaged unit blocks - including Mascot Towers and Opal Tower which were both evacuated due to cracking.

Property owners have complained about shortcomings in the private certification process, arguing profits are being prioritised over quality.

But Association of Accredited Certifiers president Craig Hardy says the construction industry needs systemic reform with both Labor and coalition governments failing to ensure industry accountability.

Mr Hardy agreed under questioning that certifiers had been "left holding the can" for the regulatory failure of successive state governments with a patchwork system of amendments currently in place.

Certifiers neither supervised building work nor remained at the site full-time, making defect detection difficult.

Furthermore, the property owner - not the builder - was responsible for selecting the certifier.

Mr Hardy said a diverse range of practitioners across the construction process - rather than solely accredited certifiers, as is currently the case - should be obliged to take out professional indemnity insurance.

Low confidence in the integrity of new projects had also pushed up insurance premiums for certifiers in NSW, he said.

"It's hard to come to any other conclusion than governments, successive governments and relevant ministers, have been asleep at the wheel while this has happened over the past 20 years.

"Continual attacks on the profession generally, regardless of who the employer is, we think (are) unjustified and unfair."

Mr Hardy emphasised the "vast majority" of certifiers acted diligently, with 47,000 certifications issued by the private sector in 2014/15.

Brett Mace, the chief executive of the Australian Institute of Building Surveyors, said a "complete overhaul" of Australian building regulations was necessary after the removal of red tape and ratification of free trade agreements prompted an explosion of new building products in the market.

"(The regulations) lack the essential rigour to actually provide safe, compliant buildings," Mr Mace told the inquiry on Tuesday.

"The sheer numbers of products, complexity of materials, construction system and services that go into buildings make visual detection of non-conforming products near impossible for almost all these items.

"The true responsibility for compliance rests with the person undertaking the work and there needs to be much greater accountability for all."

Representatives of Engineers Australia earlier on Tuesday called for the mandatory registration of engineers involved in the construction process.

Australian Associated Press