As well as the apartments, the interior had also undergone extensive earthquake strengthening to take it up to engineering requirement standards.
Architect and heritage adviser Guy Natusch, who had bought the building in 1969 and sold it to the couple two years ago, was also taken on a tour of the apartments this week.
He said he was pleased to see the building in good hands and was impressed with what they had created.
Mr Natusch bought it after it was vacated by the Napier Fire Brigade and had been vacant for a time.
He redeveloped it as a design centre and it became fully tenanted and also became a home to the Art Deco Trust before it moved further up Tennyson St in 2012.
Mr Natusch had plans for the building but at the time of selling said he had got to an age when it was becoming difficult to keep battling to try to let it out for what he hoped would be a business centre as well as an agricultural centre.
Ms Campbell said it was essential to future-proof the building as it was an important part of Napier's architectural landscape.
As an interior designer she said she wanted to retain as much of the character of the building as they could - creating a mix of the modern and Art Deco.
She retained the "curvy" beams as well as the original doors throughout.
"As an interior designer Rod gave me free rein for that."
Historical aspects of the building's life are featured throughout - like a wall feature of the original Louis Hay design plans.
Mr Earnshaw said the decision to buy the building which he had long admired had come down to two things.
"I was always keen to do something to look after it as it is a treasured building in Napier and has real charisma about it."
And some years back he had been a volunteer firefighter.
"So it was in the blood," he said with a smile.