A dispute is brewing over the prospect of the historic Gables building in New Plymouth being reroofed with corrugated iron.
Built in 1848, the former colonial hospital is a Category One historic place and traditionally roofed in wooden shingles.
Sir George Grey, a New Zealand governor during the 1840s, had the Gables built to provide care for Māori and Pākehā patients as part of his policy of encouraging the assimilation of Māori into European culture.
It is the only one of four such hospitals built in the North Island still standing today.
Designed by the architect Frederick Thatcher, it is made of heart rimu and brick and has steeply pitched roofs and decorative cross-bracing typical of the Anglo-Gothic style.
New Plymouth historian Ron Lambert said reroofing the building in corrugated iron would be a cost-cutting measure and unthinkable.
"I guess it's economics and to be quite honest when first I heard about it I was absolutely appalled.
"It is one of the top New Zealand early colonial buildings. It's not quite as well known as the Stone Store or Kemp House but it is in that league and it needs to be treated with the dignity it deserves and that's not corrugated iron."
Mr Lambert said corrugated iron would ruin the building's entire aesthetic.
"I think it will destroy it visually, completely and utterly. It's meant for shingles, shingles are what it was originally built for and it's never had anything else but shingles on it for its 170 or so years."
Located at Te Henui, the hospital was deemed too far away for many Pākehā and it dropped out of favour with Māori after it was made tapu when Te Atiawa chief Rawiri Waiaua died there in 1854.
It was converted into a military outpost during the Taranaki land wars of the 1860s and, after a period of neglect, it was bought in 1904 for £10 by Mary King, the wife of businessman Newton King.
They named it the Gables and moved it from Te Henui to Brooklands, where it is today.
It was gifted to New Plymouth after Mrs King's death in 1934.
The Kings' granddaughter Adrienne Tatham said she had an emotional attachment to the building, and her family would be horrified at the prospect of a corrugated iron roof.
"My parents lived here as did other members of the family while their houses were being built. Dad came home from the war - the 1914-1918 war - and he and Mum married and lived here while they waited for their house in Shortland Street to be built.
"I have that connection but that's an emotional one, so I have to put that to one side. I also have a long-standing gardening commitment in here and I'd hate to see the building roofed in corrugated iron because it is quite out of character."
New Plymouth District Council manager of infrastructure projects Andrew Barron said the Gables' roof was leaking and needed replacing.
He said Heritage New Zealand had given the council the OK to consider using corrugated iron, among other roofing options.
"We've been in discussions with Heritage New Zealand and it they have no [problem with iron] and it didn't have to be replaced with like for like so we are still looking at the options of which replacing like with like is one of the options."
Mr Barron said corrugated iron would cost about a third less than reroofing in cedar shingles.
Heritage New Zealand said the country had a long history of shingles being replaced or even overlayed with corrugated iron.
Central region architectural advisor Alison Dangerfield said this was one of the options discussed with the council before Christmas.
"In the early stages of our discussions we consider all options and one of the matters that seemed important to the council seemed to be the associated costs and we are mindful of the costs to councils."
However, Ms Dangerfield said Heritage New Zealand had reconsidered its position and would be recommending the roof be replaced with shingles.
"I have since looked at the materials, the significance of the building, the proposals and looked at our heritage principles and referred back to charters and the conservation plan - particularly the conservation plan - because that gives direct advice for work to this building and have really come to the conclusion that shingles are the best option for replacement if replacement is needed."