WHY IS HERBERT GARDENS BUILT OF CONCRETE?

HG Newsflash 18 November

 

                                     

New Zealanders are remarkable people. They were among the first in the world to use concrete in construction; the lighthouse on Burgess Island, built in 1882, was a pioneering use of pre-cast blocks. At the same time, pioneer engineers were experimenting with reinforcing concrete – the Sacred Heart Cathedral in Wellington, built 1895, is an example of this.

After that, reinforced concrete really took off. It has many advantages.  It is fire-resistant, looks good once clad, and if well designed, it can withstand earthquake movement, because of its inherent strength. It has much better sound-proofing than other materials.  It transfers heat and cold more slowly, too, reducing the need for high-maintenance air-conditioning.  So, by the late 1920s, concrete was the choice for building everything from bridges to public buildings that were as much as three stories high.

In 1964, when Herbert Gardens was designed by Biggs, Power and Clark, and built by P. Graham and Sons, using reinforced concrete for a high rise building was still a novelty. People used to gather on the Terrace during office lunch hours, to watch the building grow. Unusually for that time, too, it was a slab and core construction, where the floor/ceiling slabs were built around a core.  It was a method that did not become common until the 1980s.

The core has to be very strong, as it takes a lot of stress; it is where the lifts are sited, for a start.  The floor slabs have to be connected to it very firmly. The problem is that concrete “creeps” over time, and this stresses the connections. And this means that after sixty years of withstanding wind, heat, cold and earthquakes, it is time to fix the slabs more firmly to the core.

It is not an easy process. There was much research, into old photos and news reports as well as architectural drawings, and on-site tests had to be carried out. Then the job had to be analysed in detail, with many drawings made. It is extremely important to know exactly where the reinforcing has landed after all these years of creep. Meetings for workshopping have been frequent. And when the job starts, it will involve a lot of testing, and a lot of drilling. And drilling means a lot of vibration, which can shake off masonry dust and ceiling plaster – plaster that may have asbestos in the mix.

But it will be worth it, to return Herbert Gardens to the grand lady that aroused such interest and admiration back in the mid-1960s.