Neil Patel who has been fined for altering a historic building without consent.

The damage to the outside of a heritage-listed Wellington building has cost the owner and company $69,000.

Naginbhai Neil Ghelabhai Patel and Ganesh Superannuation Fund had bought the century old Sir James Elliott House on Kent Terrace in 2013 and began work to convert it to apartments.

The historic building had been the home of the Royal Australasian College of Surgeons for 25 years.

Sir James Elliott house on Kent Tce now empty after conversion work to make it into apartments was halted.

The prosecution by the Wellington City Council under the Resource Management Act and the Building Act was for converting a commercial building to residential without consent and for unconsented work done to the exterior.

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The building is a category one historic place and the facade cannot be altered without permission.

Patel and the company pleaded guilty to the charges last year.

Patel, who also owns the Shalimar Dairy in Aro Valley, was a shareholder in the company.

Wellington District Court judge Craig Thompson on Wednesday fined them $20,000 each on the Resource Management charge and $14,500 each for the Building Act charge.

He said the building was a landmark one in Wellington and deserving of respect.

Patel had begun converting the building into apartments, installing kitchens and bathrooms.

Outside heat pump and gas units were put on the building.

After a complaint was received council inspectors noted the work in January last year and issued an abatement notice. Further inspections showed the work was not removed and in fact further work had been done.

The judge said the notices from the council were ignored. An application to the council for consents was rejected as deficient.

"I accept that this is not deliberate demolition of a protected facade but it was still done in the face of clear requirements for consent. There was an abatement notice and that has still not been complied with," the judge said.

Patel's lawyer Kevin Smith said he was a first-time offender and became caught up in an earthquake strengthening issue, which he was told could cost up to $800,000 to bring the building up to 100 per cent of the code.

Smith said the damage was minor and the structure of the building was not damaged.

Outside court, Patel said he had found working with the council on the building and consents to be very difficult.

The current consent process was "bloated, strenuous, and inefficient," he said.

"Developers and consultants are becoming frustrated and this is hurting, not helping, the current housing shortage in Wellington."

Patel felt harshly treated by the council, and hoped in the future he would be able to work with the it in a positive way.

The building was designed in 1913 by notable New Zealand architect William Gray Young, who was president of the NZ College of Architects in the 1930s.

Gray was also responsible for designing such buildings as Knox College in Dunedin and Turnbull House in Wellington, and had designed Elliott House for the Wellington surgeon.

Elliott occupied the building as his home, consulting practice and surgery until selling it in 1960.

The building had been assessed as earthquake prone in 2013 and Royal Australasian College staff moved out.