Law firm Thomson O'Neil & Co in Eltham this week vacated its High Street offices after a fire police say was deliberately lit caused extensive damage under the building.
Neal Harding, a partner, told the Stratford Press he was called to the scene shortly after the fire was reported.
The first call said the dental centre was ablaze, but he says it was soon apparent that the fire was under their side of the building.
``We did not lose anything of value, but the rafters under the floor and the floor are badly damaged, so we are moving out.''
According to the police the fire started after a lit piece of paper was thrown into a filing room under the building. No valuable files were lost, says Neal.
The reception remains on the premises, using some of the dental centre's empty office space, but the rest of the staff has moved into the old town council building in Stanner Street. Contact numbers remain the same, for now, says Neal.
``The insurance company is currently working through the process of deciding whether to demolish and rebuild or whether the building can be fixed.''
The adjacent Eltham Dental Centre only suffered smoke damage. It closed on Monday for a clean-up but was in full operation again on Tuesday.
The Eltham Fire Brigade was called to the scene just after 11pm on Sunday where they battled the fire for close on 1 hours.
A 14-year-old boy has been charged with arson. He appeared in Hawera District Court and was referred to Youth Aid.
Neal says he doesn't suspect a personal motive against anyone in the building.