He was unable to get in touch with the new owners and was unsure of their plans for the site, Mr Hamilton said.
It had been a tough decision and they would be doing everything they could to help their two full-time and six part-time staff find new jobs, he said.
"There's been lots of tears and lots of whisky. I haven't slept for the last month or two -- there's been a bit of pressure and we just have to work out what's happening and get through it.
"We just can't put our staff and customers at risk any more."
A garage has been on the site since 1949, when Roly Warrington set one up at the rear of the section.
The existing garage was built in the early 1960s.
Mr Hamilton and his wife took over the garage from Matt Cutfield four years ago.
Mr Cutfield's father Bruce, who bought the garage from his son before selling it in January, said he never intended being a long-term owner.
There had been nothing to indicate the building was not up to code, Mr Cutfield said.
"There was nothing about it being earthquake-prone at all, no one even talked about it."
"It's been there for many years, it's been through some pretty big shakes and there's no cracks."
The building was still sound, he said. "People don't need to be particularly scared, if you got an earthquake that big half the Wairarapa would fall over. It's pretty solidly built."
It would cost "six figures" to bring the building up to code, Mr Cutfield said.
He was unsure of the new owners' intentions.
The new owners were contacted but had not responded by the time this issue went to print.
The property is listed on the Carterton District Council's Earthquake Prone Building Register.
Council's planning and regulatory manager Milan Hautler said being under code did not necessarily mean a building was too unsafe to use.
"It [a building] may be on our list as earthquake-prone but not be bad enough to vacate or get it done right away." Buildings that are less than 34 per cent of the building code must be improved by 2021, unless a building consent is applied for earlier.