Taking care . . . Waitaki District Council heritage adviser Heather Bauchop and project and assets officer Grant Rhodes say it is important to look after Oamaru stone buildings. PHOTO: RUBY HEYWARD

The Waitaki District Council is using new techniques to clean old buildings.

The council recently started cleaning some of its historic buildings by applying a ‘‘mosskill product’’, project and assets officer Grant Rhodes said.

The product worked away slowly at the moss over time, and ‘‘mother nature’’ would wash it away with the rain, Mr Rhodes said.

It was a long process, slowly working over the next six to 18 months, he said.

Depending on the level of build-up, some buildings could require multiple treatments.

The moss-kill product would be followed up by a ‘‘passive’’ steam clean — a method the council would use sparingly.

Over two weeks, nine different buildings in Oamaru were treated, many of which had Heritage New Zealand category 1 and 2 listings.

This included the Waitaki District Council building, the Centennial Memorial Rooms, Oamaru Blue Penguin Colony, part of the Oamaru Opera House, and other council buildings along Itchen St.

Though not registered under Heritage New Zealand, the North Otago Returned and Services Association (RSA) building and Drill Hall were also given a freshen-up.

Waitaki District Council heritage adviser Heather Bauchop said it was a ‘‘thoughtful process’’.

When a historic building looked shiny, white and new, it was likely to be a sign of damage more than anything else, Ms Bauchop said.

Many years ago, some historic buildings were cleaned with water-blasters, which were now considered a big ‘‘no-no’’, Mr Rhodes said.

‘‘If you don’t look after them in the correct way, the buildings aren’t going to be around for future generations,’’ he said.

‘‘These are beautiful buildings and if you can get them to last hundreds and hundreds of years, that’s the aim — rather than being gone in 50 years like a modern building under the Building Act.’’

Ms Bauchop echoed this.

‘‘You can’t build like this any more. If you lose them, they’re gone,’’ she said.

‘‘The architectural skill and design and detail, that’s never going to be repeated in the same way.’’