Apartment complex rises from grain silo's kernel

Construction manager Gary Young (left) and site manager Ron Triezenberg outside the Northern Roller Mills site. Picture / Greg Bowker

An old grain silo will soon be home for Auckland apartment-dwellers.

Manson Developments will soon finish converting the 12-level silo in the central city into 138 apartments.

Manson has three separate developments on the site: the Silo apartments, the Lumley office tower and retention of the historic facade of Northern Roller Mills building, which is being converted into a carpark.

Holes have been cut in the concrete walls of the 1940s silo and 2.5sq m balconies attached to the side.

Internal fitouts of the units are also well under way. Workers are lining walls and are almost ready to install dozens of kitchens and bathrooms.

Work at the Northern Roller Mills site in Fort St started with a crane lifting a digger on to the top of the building. For 15 months, the digger slowly crunched its way down through the centre of the silo, demolishing the internal storage network of honey-combed concrete and reinforcing steel.

"The digger was larger than any of those honeycombs so it couldn't fall through the centre," said construction manager Gary Young.

Gas torches were used to slice through steel reinforcing once the concrete was removed. "In some cases, those rods were 30ml thick and solid steel bar," said Young.

Steel props were erected on the inside of the silo's exterior walls to support the structure while it was gutted.

The exterior wall is 24cm thick concrete, and opening up each floor to the outside was another challenge.

Railing was attached to the outside of the building to guide a concrete saw which was used to carve out openings for each apartment.

Accuracy was paramount, Young said. The cutters' worst nightmare was striking a reinforcing bar.

Aluminium doors will soon be installed and cedar shutters fitted to complete the job.

Inspiration for the novel silo-apartment conversion - the first in New Zealand - came from Manson staff who saw that a series of circular side-by-side silos in the United States had been converted into an hotel.

"But that was easier," said Manson chief Ted Manson, "because structures were built between the silos, whereas we are building inside the silo.

"This has only been done two or three times in the world."

The apartments are not large, ranging from a tight 17sq m studio and a 35sq m one-bedroom unit. Larger two-level apartments were built on the top and ground floors.

The units all sold, for a minimum of $135,000.

Floors were built within the silo by laying metal plates then pouring the concrete in place. Stairs were precast off-site and lifted into the silo.

The first residents are to move in around Christmas.

Manson bought the site from Goodman Fielder more than two years ago.