A Christchurch man who extensively renovated a beach house in the Awaroa Inlet has been fined for failing to gain building consents.

A "classic Kiwi renovation" turned in to an expensive "nightmare" for a Christchurch man who failed to get consent for the building work done on his beach house in the Abel Tasman.

Semi-retired Christchurch businessman Volkmar Wollenweber​ appeared in the Nelson District Court on Wednesday on six charges of carrying out building work without a building consent and three charges of carrying out restricted building work without a license on his Awaroa Inlet property. He was fined $17,250.

Defence lawyer Marty Logan said Wollenweber never intended to breach of the building regulations as he hadn't anticipated doing such extensive work on the house.

"What this has turned into is almost a classic Kiwi renovation nightmare."

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Wollenweber purchased the property with his wife, with the plan to keep it as a bach.

"The intention was he would give it a lick of paint and repair the cracks in the stucco cladding but the rest of it was to make it more comfortable, installing insulation in the walls, ceiling and under the floor and double glazing for the windows."

Logan said Wollenweber started in one room where there was a terrible smell due to a rat infestation in the walls and the floor "bounced like a trampoline" due to rotten piles.

He then discovered the cladding was not watertight and needed to be replaced and Logan said things "steamrolled" from there.

The first time the Wollenweber's used the fireplace smoke came out of the chimney breast revealing structural problems with the chimney. The wetback fireplace disintegrated and flooded the house. Daylight was visible through rusted out parts of the roof, which needed to be replaced.

"It wasn't a pre-planned complete rebuild, it was just one thing after another."

Logan said given that Wollenweber was replacing "like with like" he didn't think consent was needed. In hindsight, he wished he had demolished the bach and started again.

Last November, a Tasman District Council investigator visited the property following reports of unauthorised building work.

It was observed the building had be re-clad, the roof was at a different angle, a kitchen had been built outside, an outdoor shower had been plumbed in, there were new piles under the house and a new logburner had been installed. No building consents had been applied for or issued.

Wollenweber told the council he had personally done the building work, that the entire roof – including trusses had been replaced and no advice had been sought from the council.

BRADEN FASTIER/STUFF Tourists and visitors enjoy Awaroa Beach in the Abel Tasman National Park, which is also known as New Zealand Beach after a crowdfunding campaign succeeded in buying the beach back from a previous owner.

Tasman District Council lawyer Nathan Batts said it was submitted that Wollenweber "genuinely believed he did not have to obtain a building consent", which the council found difficult to accept.

"Mr Wollenweber comes from a family of builders and when he started working in New Zealand it was in the trades, tiling, painting and renovation."

Batts said Wollenweber was clearly familiar with the Building Act and its requirements as he sought to rely on the statutory exemption of maintenance and repair.

The work done on the house amounted to a "complete rebuild" of the existing dwelling, along with significant new additions.

Judge David Ruth said the court's view was that Wollenweber knew "full well" what his obligations were and chose to ignore them.

"This wasn't a weekend do-up, this happened over months."

He said it was concerning that Wollenweber had admitted some of the work carried out, particularly in relation to load bearing piles had not been to standard.

"You must be held accountable for what you have done to promote in you a sense of responsibility and to denounce your conduct and deter others from doing it."

He agreed Wollenweber had taken some responsibility for the problems with the build and fined him $17,250. In accordance with the Building Act, 90 per cent of the fine would be paid directly to the Tasman District Council and the remaining amount to the Crown.