The ministry's preventing falls from height project sought to tackle falls from height on construction sites, which it estimated cost the country $24 million a year.
The majority involved workers falling less than 3m, mainly from roofs and ladders, which meant more scrutiny was on safety in those areas.
The ministry wanted to see more use of building platforms and scaffolding in place of ladders, and additional steps to protect roofers, among other changes.
However, Versatile Homes and Buildings general manager Peter Gouverneur, of Dunedin, said the "big push" also risked adding thousands of dollars to the cost of a new home.
That was because scaffolding would need to be installed during construction of even single-storey homes, to ensure the safety of workers, he said.
"It is going to put the price of housing up. It'll put at least a couple of thousand dollars on per house."
Otago Master Builders Association president Mark Ward said the focus on small falls of less than 3m meant use of ladders and saw-horses was being targeted.
Builders were now encouraged to replace old ladders with new platform ladders, and not stand on saw-horses while working, he said.
"They reckon instead of standing on a saw-horse, you're meant to have two of them and have two planks on them.
"But, you know, if you can't stand on a bloody saw-horse ... you probably shouldn't be in the industry."
The project was unveiled late last year, but inspectors had only been out enforcing the new requirements since July 1.
That led to one unnamed employer, responsible for a Mosgiel residential building site, being spoken to this month by a ministry inspector following a complaint about unsafe work at height, a ministry spokeswoman confirmed.
The inspector also visited the site, but no further action was taken.
Mr Ward said he had been warned inspectors would be "out and about" enforcing the new rules, and that an additional 50 inspectors had been recruited nationwide for the tough new stance.
He was aware of the cost of falls to the industry, but also warned the new requirements would add costs to the building industry.
"But our point is there's a lot of home handymen who get lumped in with us.
"We try to be as safe as we can, but not to that extent."
Mr Gouverneur said his company was "definitely taking it seriously", and it was hard to object to the new approach "when you're talking about the safety of people".
He expected some companies would be "dobbing-in" others, if some firms attempted to avoid the new requirements and the costs that came with them.
"I think there's a strong signal going out now from the Department of Labour [Ministry of Business, Innovation and Employment] that doing nothing is not an option."
The ministry spokeswoman said the Government had allocated $37 million to workplace health and safety over the next four years, funding a 20% increase in health and safety inspectors - to 180 nationwide - as well as other initiatives.
Ministry information showed more than half the "unacceptable" number of reported serious harm accidents involved falls of less than 3m, mostly from ladders or single-storey roofs, and mainly on residential building sites.
The crackdown meant inspectors were targeting workplaces with inadequate precautions to prevent falls from roofs and other structures, or those using ladders or trestles instead of more appropriate alternatives, including scaffolding or elevated work platforms.
Builders, roofers, electrical workers, painters and decorators at high risk of falls of less than 3m would all be targeted.
"If there's a chance of a fall - from any height - precautions have to be taken."
Dunedin city councillor Syd Brown, who is behind a 10ha residential subdivision on Hagart Alexander Dr, said he had been surprised to spot scaffolding going up at his subdivision recently.
"I've never seen single-storeyed houses get scaffolded before. You see double-storeyed ones, when they're trying to do the roofs and all that, but it's the first time I've seen the single [storey] ones."
Dunedin City Council chief building control officer Neil McLeod said the crackdown was "nothing whatsoever" to do with council building inspectors.
However, they were obliged to talk to builders about any unsafe practices they saw, and had in the past alerted ministry inspectors as well, he said.
