More to moving than meets the eye

Once the preparation work is finished on the Rob Roy, its move is expected to take just one day. Photo / Dean Purcell

Auckland's 600-tonne brick Birdcage Hotel - now known by its old name the Rob Roy - will be shifted in early September.

Bryce Irving, Fletcher Construction project engineer, and Adam Thornton from civil and structural engineers Dunning Thornton in Wellington, said they expected the hotel move to take only one day. It has to be shifted because it is in the way of the Victoria Park Tunnel job.

An acoustic wall has been built alongside Franklin Mews to screen residents from construction din and it is near that wall that the hotel will move temporarily.

The pub will be shifted twice: first in early September up Franklin Rd on a slight angle to the south to avoid street trees while the tunnel is being built and then three to four months later back to its original site above the tunnel's roof.

Work is well-advanced to strengthen it for the shift, bolting 1.8cm thick plywood to walls, steel reinforcing rods being run through the bricks and building new structural walls on the exterior.

Those walls are rising atop the existing brick plaster-clad walls on three sides of the building.

The structural walls will help hold the hotel together ready for the move and in case of earthquakes.

Thornton said that towards the end of the job, plaster would be applied over the top of the reinforcing so the walls would appear as they did before any of the work started.

But the basement is a big focus for the workforce now, with excavations around exterior and interior walls.

The ground floor has been gutted from the inside to allow access to the footings and for structural strengthening.

Brick walls are being vertically stressed with high-tensile bars inserted through holes core-drilled from the top of the building, then tightened up.

The rear non-heritage walls of the building are being coated with reinforcing concrete so these act as sheer bracing walls.

Carbon fibre reinforcing strips are being inserted into the chimney walls to provide seismic strengthening.

Concrete sandwich beams are being inserted under the building and those will soon sit on top of sliding bearings that will carry the Rob Roy along runway beams to its new temporary home and back again.

To transfer the building load on to the runway beams, hydraulic flat jacks will be inserted between the sandwich beams and the runway beams at 14 points, Thornton said.

These jacks will be monitored every metre to ensure that all points of the building remain level as it moves, he said.

Beneath each flat jack will be a sliding bearing made of a low-friction Teflon puck that will slide along a stainless steel strip fixed to the top surface of each runway beam.

The jacks will be incrementally loaded until the building's entire weight is transferred from its existing foundations on to the new beam system, Thornton said.

Irving said the building was not being lifted up. Hydraulic pushing rams will be installed between the building and the runway beams to provide the moving force. Each stroke of the rams will move the building forward by about 1.5m at a time.

While the tunnel is built under its original site, the Rob Roy will sit on temporary foundations 40m up Franklin Rd.

The transport process will be repeated when the building is moved back after the tunnel construction.

No one will say precisely what day the shift will be but Tommy Parker, NZ Transport Authority Auckland and Northland state highway manager, said 350 people were on-site at the bigger Victoria Park tunnel job this month. At its peak in November, about 450 people will be working there, he estimated.

Shanghai Lil's, the business which operated in the Birdcage, last year shut and has re-opened in a colonial-style underground bar in Parnell Village.

TUNNEL JOB

*One of seven roads of national significance identified by the Government.
*First to be constructed and due to be the first completed.
*Will increase State Highway 1 capacity between the Auckland Harbour Bridge and city.
*A 450m cut-and-cover tunnel for three lanes of northbound traffic.
*Southbound traffic will continue to use the existing Victoria Park fly-over.
*Widening motorway through St Marys Bay by one traffic lane in each direction and a citybound bus lane.
*Reconfiguring Victoria Park Viaduct for four lanes of southbound traffic.

Three historic structures are being protected by the NZ Transport Agency:

*Birdcage, now called Rob Roy Hotel, built on the original Freemans Bay foreshore.
*Campbell Free Kindergarten, Auckland's first kindergarten built in 1908 on Victoria Park.
*Jacobs Ladder built in the 19th century to provide pedestrian access down the St Marys Bay cliff face to the harbour.