Innovation Benefits Whangarei Girls

Because many schools were built prior to the current building standards the New Zealand Ministry of Education, in 1998, undertook a nationwide structural survey of all school buildings throughout the country. The result of the survey identified high priority work which was to be completed by 2001 and would further allow education Boards of Trustees to rectify any other building defects, which failed to meet their requirements, in each school’s 10 year property plan. The purpose of the survey was to identify specific structural defects that could potentially cause death or serious injury during wind or earthquake or every day loadings. As well as buildings, site structures such as retaining walls were also checked.


Geoff King, of Designgroup Architects H+K Ltd in Whangarei, has had a 15 year association with the board of Whangarei Girls’ High School and has an extensive appreciation of the history of the school and the future requirements. In 2002 the Ministry’s survey identified remedial seismic work required to strengthen the school buildings and allocated approximately 1.1 million dollars to complete the work. Working closely with the school and engineers, Duffill Watts and King Ltd, the conclusion reached was that the majority of structural work to strengthen the walls was required in order to support the heavy clay tile roof. By removing the clay roof and replacing it with a metal roof (considered lightweight under the building code) the strengthening required was reduced to selective areas. This solution had the benefit of significantly reducing the cost of the work required.

The School wanted to retain the aesthetic appeal of the original building and to achieve this Architects H + K chose Gerard Roof’s Tuffcoat Tile in Marseille Clay. The lightweight nature of the tile solved the weight issues and provided the aesthetic appeal. In addition to this the horizontal fixing of the tile provides additional integrity and security in high wind applications.

This innovative approach and collaboration between architects and engineers resulted in a saving of over 500,000 dollars that the school was then able to use in an extension to their existing gymnasium.

Whangarei Girls’ High is, by any standard, a very large building complex first built in 1920. The majority of the buildings are two stories with parts being three storied. Because the school has been built in various stages over the years some aspects connecting the building were also able to be resolved improving undercover foot traffic between levels and buildings. As an apprentice builder Ian Douglas (formerly from Douglas Roofing) worked on these buildings and during the re-roofing project was able to find both his name and the date which he had carved into rafter some fifty years before.

The roof area covers 2800 square meters requiring 5800 Gerard Tuffocat tiles which were supplied and fixed by Douglas roofing Whangarei. The new Gerard roof weighs 12.76 tons compared to the estimated weight of clay tiles removed at 70 tons. This represents a weight saving of approximately 57 tons reducing the need for major structural change.  Removing the clay tiles and replacing them was a huge task which was done in stages over a ten week period to ensure that the function of the school was disrupted as little as possible. The clay tiles that were removed were loaded into trucks using a Geda rubbish chute. The roof height ranges between 8 and 12 meters which required 2000 face metres of edge protection scaffolding including loading platforms and the Geda chute. These were all supplied and erected by Northland Scaffolding.


Earthquakes.

New Zealand lies on the boundary between the Pacific and Australian tectonic plates which basically follow the country’s mountainous areas, diagonally from east to west. The eastern areas of this divide generally experience shallower earthquakes than the western areas as indicated in figure 1. It is estimated that between 100 and 200 earthquakes are significant enough to be felt each year. Most earthquakes which cause damage are of a magnitude of 6+ and we generally experience one of these per year. A magnitude of 7 occurs about every 10 years and a magnitude of 8 about once a century. The largest known earthquake in New Zealand was the Wairarapa earthquake in 1855 which was an estimated magnitude of 8.2. The biggest New Zealand earthquake since instrumental recording began was the 1931 magnitude 7.8 Hawke’s Bay earthquake with a death toll of 256. New Zealand is fortunate that whilst experiencing earthquakes in a similar Richter scale range to other countries we have not suffered similar loss of life. Much of this comes down to three factors. The standards of our buildings and building code, the low density of our population and for want of a better expression, “luck”.



Wind.

The “wind uplift” performance of roofing products is becoming an increasingly important factor in New Zealand as more and more people build on sites that take full advantage of our undulating topography and coastal environment. All Gerard roofs feature interlocking tiles secured in place with a unique horizontal fastening system. The result is a very strong roof with superior wind resistance, which allows specification in very high wind zones. High winds blowing over a roof cause a difference in air pressure between the inside and outside of the roof. The stronger the wind, the higher the pressure differential. This results in “wind uplift” perpendicular to the roof which is the primary cause of failure in roofs with vertical fastenings. In this instance the clay tiles were fitted with vertical fastenings.

Designgroup
Architects H+K Ltd.

Architects H+K is a member of Designgroup New Zealand Ltd, an association of architectural practices located throughout New Zealand. Members have the ability to call on a range of specialist services and extended resources available to benefit their clients.

Designgroup architects h+k offer specialist and personal service in the fields of architecture and resource management. The 10 team members have extensive knowledge in areas of healthcare, education, commercial, residential, interior design, town planning and project management and have a commitment to excellence in design and project delivery.

Over the last 22 years they have established a reputation of providing sound architectural services to a wide range of clients that includes Government departments, state owned enterprises, local authorities, hospital boards, school boards and other industrial and commercial organisations, while also providing an extensive service in residential architecture.

Designer:
Designgroup Architects H+ K Ltd
Whangarei
Telephone: 09 438 8426
michelle@ahk.co.nz
www.ahk.co.nz

Engineer:
Duffill Watts and King Ltd,
Telephone: 09 630 4882

Roofing Manufacturer:
Gerard Roofs
Profile: Gerard Tuffcoat
Colour: Marseille Clay
Telephone: 0800 104 868

Roof Installer
Douglas Roofing
Whanagrei
Telephone: 09-438 8485