Auckland's historic Birdcage pub is on the move - 1.8 metres at a time.

All 740 tonnes of the 19th Century pub and hotel are being moved 40 metres in a painstaking process today to make way for the Victoria Park tunnel project.

Once the tunnel is complete, the entire structure will be moved back to rest on top of the tunnel.

The Birdcage, also known as the Rob Roy Hotel, was built 124 years ago and has been designated a heritage building.

It is being moved on a specially designed concrete track with a greased teflon surface at a cost of $2.5 million.

Dunning Thornton Consultants director Adam Thornton said the building was initially shunted by two 30 tonne hydraulic rams which could move the building 1.8m at a time. By 11.45am, the Rob Roy had moved 3m.

"It is a slow process. Speed is not the issue here, the important thing is that it gets to the other end, unstressed," Mr Thornton said.

He said an engineer was monitoring the stress levels that each bearing was under at all times.

Mr Thornton said each of the bearings sat on a hydraulic pressure pad that could be adjusted, shifting the 740 tonne weight of the building to other bearings if necessary.

"Some of them have changed because it only takes a minute change in the foundation beam and the pressures can increase and decrease," Mr Thornton said.

New Zealand Transport Agency (NZTA) State Highway manager Tommy Parker told reporters that it was "so far, so good".

"Everything is going to plan," Mr Parker said.

He said today was a "unique challenge" for NZTA staff and they were excited.

Mr Parker said the roof of the tunnel had been strengthened to take the weight of the Rob Roy but the weight of the fill used to cover other parts of the tunnel was heavier.

"It's a piece of history and we're really happy to keep it in its original position," Mr Parker said.

The Rob Roy

The Hotel and bar was built in 1885-1886 in Auckland's Freeman's Bay when Victoria Park was a busy industrial area that included ship builders, sawmills, a brass and iron foundry and glass works.

The Hotel was built by Samuel Jagger who employed architects Edward Mahoney & Sons, who designed many of Auckland's early hotels as well as St Patrick's Cathedral.

The Rob Roy had three storeys. The basement housed the kitchens, pantry, beer and wine cellars and servant's diningroom. The ground level had a bar, three sitting rooms and a serving room. Upstairs were nine bedrooms and another sitting room.

After Mr Jagger's death, the hotel was owned by Hancock and Co until it was sold to Tony White and John Banks in the early 1980s. It was later renamed the Birdcage Tavern. In 2002 the NZTA bought the Rob Roy/ Birdcage to extend the motorway.