Stephen MacKnight, whose family is involved in restoring historic buildings in Dunedin, said the state the 135-year-old building was in when its roof collapsed should be of great concern.
Engineers said wet and rotting wooden support beams and crumbling bricks and mortar - the condition of which was not assisted by the ingress of water and birds into the building - had, with time, caused the collapse of the roof on to the second floor.
No-one was in the building at the time, although the Dragon Cafe on the ground floor of the property was open until early that morning, and was due to open again later in the day.
Dunedin City Council chief building control officer Neil McLeod said the council had no policy to inspect proactively the structural integrity of ageing vacant buildings, and only acted to ensure a building was safe once it had been made aware of a danger.
The council had no heritage building risk register, and setting up a regime to inspect the structural integrity of every building over a certain age in the city would involve a significant cost. He was not aware of any other council that had such a policy.
But Mr MacKnight said while Dunedin had a large stock of historic buildings, probably fewer than 10 in the central city were of great concern in terms of being dangerous, and they were not hard to pick.
"I think anyone could walk the streets of the central city and very clearly see the buildings that need inspecting. They are vacant; they are not being maintained; water and pigeons are getting in."
Some demolition by neglect was going on in the city, he said.
People were buying old buildings they intended to demolish but, Mr MacKnight said, to avoid arguments with the Historic Places Trust they kept them without maintaining them, until the buildings become so derelict they became dangerous and had to be demolished to address safety concerns.
He believed the situation could be addressed relatively easily, by the council either requesting owners to carry out an inspection and report back, or sending an engineer to do an inspection and sending the owner the bill.
The co-owner of the Rattray St building, Lincoln Darling, said he had never seen any outward indication the brickwork in the building was about to collapse, and the roof had been replaced within the past six years.
Other maintenance was regularly done to the building.
He said people might have got into the building from the neighbouring Crown Hotel, and it was possible they had opened windows, which could have been how birds and water got into the upper levels.
He said the owners' intention had always been to restore the "beautiful" old building, and they still hoped to do that.
"We hope that we will be able to rebuild and the institution [of the Dragon Cafe] will remain. We don't want to see it demolished. Of course, we have to make sure the building is safe first."
Mr McLeod said people who bought old buildings were not legally required to check their structural integrity, but they were responsible for ensuring people's safety in and around them.
At present, little was protecting people using old buildings from their collapse, other than landlords making sure it was safe to be inside or near.
The most common problem with old buildings was the deterioration of unreinforced masonry.
"After 125 or 135 years, often with limited maintenance, buildings are not very well stuck together.
"Also, they often have issues with leaking roofs and rotting timber."
Buildings should have warrants of fitness, but that related to systems such as fire alarms, smoke protection, escalators/lifts, etc, rather than structural integrity.
Dunedin Mayor Dave Cull was unable to be contacted yesterday for comment on the city's policy on inspecting historic buildings.
