Garage owner Chaz Forsyth said he had heard noises during the night, but had not thought anything untoward was afoot.
"We heard quite a lot of thumping and banging, we thought it was some animal running around on the roof.’’
Instead he woke up to a collapsed garage, a crushed vehicle and a visit from the fire brigade.
A fire crew from Willowbank station cordoned off the Evans St garage about 7am and contacted the Dunedin City Council.
Mr Forsyth said he was concerned for public safety and had taken advice from the council inspector who visited.
The garage was standing when he returned home from a meeting about 10pm on Monday.
A spokesman said the council would be issuing a dangerous building notice and changing the traffic plan for the street to allow remedial work to be carried out.
