The mill's roof, corrugated iron, door and window sills all recently received a new coat of paint as part of ongoing maintenance to protect and preserve the historic building.
Clarks Mill is New Zealand's only surviving water-powered flour mill (though now run by electric motors) with early machinery still substantially intact.
The mill was built about 1865 as part of the nearby Totara Estate and has been owned by the trust since 1977.
The trust's heritage destinations manager, Paul McGahan, said considerable work had been done by an enthusiastic group of volunteers over recent years on the interior of the building and it was pleasing to finally upgrade the exterior.
A further improvement is about to be made with the installation of safety barriers around the flour mill machinery.
This will enable the mill to be operated, giving visitors a glimpse of how an early flour mill worked.
Dedicated restorers tend the wooden sifters, metal rollers and the labyrinth of belts that power the machinery.
The mill is significant because it is the second-oldest in New Zealand.
Mr McGahan said the trust was considering holding a series of open days next summer so the public could experience the workings of Clarks Mill.
The mill and its machinery provide an insight into early industrial processes in New Zealand.
Clarks Mill is now closed for winter but volunteers will re-open the building for public viewing between 1pm to 3pm each Sunday from October to April, or otherwise by arrangement through Totara Estate.
