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.
The gallery and full exhibition programme will remain open to the public during the renovations.
The unique architecture of the building such as distinctive roof lines will be retained with special detailing.
Aside from minor alterations, the current roof is largely the originally built roof from the 1970s.
The building was designed by local architects Natusch, Wilcox & Co and was expanded to its current size in 1975.
The spokesman said disruptions would "be kept to a minimum, although there may be some noise and some programmes may need to be moved around the building as required".
Three exhibitions are being held over summer: Leanne Morrison: Off the Edge, Richard Brimer: Harvest and Andy Leleisi'uao: Kamoan Mine.