Council announced last week it would close on May 10 and reopen on May 27 at James Cumming Wing hall.
It would be at the new location for 18 months.
Regulatory and community services general manager Ian Davidson-Watts said the mould did not present an immediate risk to the public.
Gore’s council had flagged spending $1.1 million in its 2018-28 10-year plan to fix the roof.