The sheer walls of Blackwatch Pass are getting a makeover, with visiting contractors scaling the cliffs to remove loose rock and vegetation.

The link from North Shore Road to Hamilton, with the dramatic overpass leading to Government House, opened in 1934, and has been occasionally subject to falling rocks, such as in 2015.

Plants can bring down rubble, along with gradual weathering of the exposed stone.

The road has closed during the daytime for remedial work conducted by a team from Cimota Inc in Canada, who rappel the slopes of the pass on high-strength ropes with pry-bars and picks to dispatch trees and rocks.

According to a Public Works spokeswoman, the method is known as rock scaling, and is closely supervised by ministry staff, plus a rock slope expert.

After the work, masonry walls, anchors or “shotcrete”, where concrete is hosed onto a surface, will be deployed as needed.

Work began on April 3, and is expected to be completed by April 28.