Hastings City Art Gallery will begin installing a new roof next week.
The current roof cladding has "reached the end of its serviceable life" and will be replaced with galvanised iron for the pitched roofs and membrane roofing for the flat roofs starting next week.
Renovations are expected to last until the end of August.
The total cost for the new roof including design, engineering compliance, building consent, air conditioning and the roof itself is about $1.35 million, said a Hastings District Council spokesman.
The new roof is expected to last at least 50 years.