A grand mansion of almost hotel-like proportions is rising on Auckland's northern outskirts in a job so big that a commercial-grade tower crane is swinging above the site.

The 20-metre crane from Atlas Cranes Northland is on the site of the house, costing around $10 million, being built on a 24-hectare rural property at Coatesville.

In one of Auckland's most expensive residential construction jobs, award-winning PSL Construction is building the house, which has just more than a tenth of a hectare of floor space.

Phil Leach, PSL chief, said: "The crane is on the job to speed things up. There's been a lot of lifting. It's a very large home. We do believe it's the only home in New Zealand with a tower crane up.

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"The home consists of about six bedrooms including a guest wing. We have a helipad and helicopter hangar out the back and also obviously a swimming pool which works quite nicely here as well.

"This home is approximately 1200sq m plus a [helicopter] hangar and garaging. We have a pretty large team here to get the project moving along. We're around 30 to 40 people a day. It's definitely the largest home we have built," said Leach, whose company has three times won the supreme Master Builder of the Award.

Chris Hunter of builders NZStrong described the house plans as "amazing. Great to see little old New Zealand getting this scale of residential investment."

Leach said 10,000 to 12,000 concrete blocks had been laid, around 400 truck-loads of concrete had been delivered, and the whitest concrete he had ever seen was created to create dramatic marble-like internal columns which were poured from the bottom up to eliminate the potential for air bubbles.

PSL is working with Bannan Construction, a specialist in high-end architectural concrete homes and in situ concrete. Leach said Bannan built the white columns from self-compacting concrete, poured through a tube from below.

"Bannan has been critical to this job, on the concrete walls and white fins or columns which hold up the house," Leach said.

Instead of aluminium, all joinery has been made in more expensive, powder-coated steel.
But Leach said big floor-to-ceiling stacker glass sliding doors could be easily opened because the fittings were so well made: "It's the quality of the rollers."

Phil Leach of PSL Construction on the Coatsville site. Photo/Doug Sherring
Phil Leach of PSL Construction on the Coatsville site. Photo/Doug Sherring

The joinery was manufactured by Takanini-based Crittall Arnold which specialises in bespoke steel-framed windows and doors.

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Leach said construction techniques being used were more like those on bridges or commercial sites.

Up to 40 workers are on the giant build at Coatsville. Photo/Doug Sherring
Up to 40 workers are on the giant build at Coatsville. Photo/Doug Sherring

"Post-tension concrete beams are being used in the outdoor terraces. That's unusual in a house, it's used in jobs more like bridge-building. The flooring will be timber, terrazzo on some of the terraces, tiles and carpet," Leach said.

The property is entered via a grand sweeping drive more than a kilometre long, climbing towards the hilltop house, in front of a large grove of trees.

Plans by Hulena Architects show a covered hotel-style port-cochere to shelter people at the front door, then a grand entry foyer with separate coat-room and guest bathroom.

The 20m crane, swinging on the huge site north of Auckalnd. Photo/Doug Sherring
The 20m crane, swinging on the huge site north of Auckalnd. Photo/Doug Sherring

Formal dining and formal living areas are directly ahead, facing north towards sweeping views of the rolling green countryside, east loggia and pool.

The main wing of the house has a kitchen with separate scullery, then rooms to the north for casual living: dining/living on one of a grand double-sided fireplace, then another living area on the other side. Outdoors, a north terrace and northern loggia flank these informal areas.

A separate but connected wing behind contains the library/media room, wine cellar and a fireplace. On the floor above is an office with its own deck and a large file storage room.

On the other side of the formal dining area downstairs are bedrooms, each with en suites, separate dressing areas and extensive storage. The master bedroom is upstairs, facing north.

Separate rooms have been designed for linen, laundry and storerooms and a drying terrace is created outside the laundry.

In a separate wing, three double-garages have been built, with the helicopter hanger and landing area out to the back of the place. The walls of the hanger are up but the floor has not yet been built.

Leach said the site was ideal to work on and a wet summer had created few problems.

"We arrived on the site in March last year but it was already cut down," he said of earthworks carried out by another contractor.

The owner, an Auckland businessman, said the job would take about two years to complete and he expected to move in early next year.

Grand design:
• House by Hulena Architects
• 1200sq m plus extra garaging
• Helicopter hanger and helipad
• 18m x 6m in-ground swimming pool
• Commercial-like building techniques used
• 400 truck-loads or 2000cu m of concrete
• Up to 40 people there each day
• 10,000 to 12,000 concrete blocks used
• Four grand floor-to-ceiling fireplaces 7m high
• Foundations up to 12m deep
• One loggia has an 18m steel roof span
• Work started last March
• Due to be finished early next year