An office building in central Wellington is being evacuated, after engineers expressed safety concerns.

Workers have been ordered to leave 79 Boulcott St, getting their marching orders at 2pm, and being told they'd have to be out by 4pm.

Wellington City Council building resilience spokeswoman Jacqui Hastie said they were conscious of the lessons from the Christchurch earthquake, and weren't leaving anything to chance.

"Engineers have looked at the building, and they want to do further investigations on it.

"For now, they're not confident saying it's safe to occupy. So as a precaution they've asked the tenants to evacuate."

Hastie said she couldn't comment on what the specific problems were, but that engineers had been doing routine work when they came across something they "weren't expecting".

The tenants have been told they'll be out of the building for at least 48 hours, by which time they'd be able to get more accurate information.

Some workers, speaking on the condition of anonymity, said they'd been told cracks had been spotted in the walls.

Many staff took office equipment with them when they left, and plan to work from home until further notice.