The sway-backed roof on the Whangarei Museum in the Kiwi North complex needs serious surgery to prevent it springing a leak.
A feasibility study is under way on options to repair the swooping roof which is in such bad condition staff are worried about possible damage to the exhibitions and other inside spaces.
Footage filmed by a drone sent over the building has revealed the state of the existing 30-year-old roof, operations director Allie Fry said.
"It's done very well for this long but it's a complex roof and repairing it isn't straight forward," Ms Fry said.
The district's collection is considered safe for now, she said.
"We're just trying to get there before it deteriorates any further."
The feasibility study is aimed at identifying whether to repair or replace the roof, and the costs of also building a cafe, offices and a large community space under it.
Some staff have been housed in portacoms for years and the current museum building does not have a large, versatile space for workshops and other interactive events, Ms Fry said.
"The roof is a 'have to', and so are maintenance of the Clarke Homestead and Oruaiti Chapel. Some of the others are a "want to'."
The Heritage Park component of the museum has a collection of historic buildings, including the large colonial villa known as the Clarke Family Homestead.
The kauri homestead, built 1886, was lived in by three generations of the Clarke family on land that was farmed for nearly 90 years before being bought by the museum in 1972.
The tiny, octagonal Oruaiti Chapel is made from a single kauri log and thought to have been the smallest chapel in New Zealand.
It was originally situated near Mangonui in the Far North and was moved to Heritage Park in the 1980s.
Maintenance on those two grade two New Zealand Heritage-listed buildings can not be put off for too long.
"We've had professional conservation and heritage architecture plans drawn up and they and the roof are our main focus," Ms Fry said.
Once the priority work and costs have been established, Kiwi North strategy and finance director Linda Ace will write up applications to various funding sources, including Lotteries, Oxford Trust and Foundation North.