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Vernacular architecture is any localized architectural style addressing local building needs through the use of local materials. It is often in direct response to the local environment. An important part of every country’s unique heritage, it should be preserved for future generations. Unfortunately natural and human-induced threats are causing the loss of many vernacular sites in South Africa. The African Conservation Trust (ACT) in partnership with the University of KwaZulu-Natal (UKZN) have been using 3D laser scanning technology to create permanent digital records of South Africa’s threatened vernacular architecture. Laser scan data is used to isolate building weaknesses, take accurate measurements to determine severity of damage, and create detailed cross sections to assess structural integrity. This information can be used to assist land owners and heritage management authorities in the preservation of heritage sites.
Corbelled houses
The corbelled houses in South Africa’s Northern Cape Province are the earliest examples of vernacular architecture in South Africa. The unique structures were built by the early Dutch settlers who arrived in the harsh semi-desert landscape from about 1820. The settlers found that within this landscape trees were sparse but stones were aplenty. To adapt, they made use of an ancient method of construction known as corbelling. In corbelled architecture successive courses of flat stone are placed atop one another, with each row moving further inwards until they almost met at the apex. A single, larger slab is used to cover the remaining hole.
Examples of corbelling can be found across Mediterranean Europe; and the corbelled Trulli Houses of Arabello, Italy have been inscribed as a UNESCO World Heritage Site. The corbelled houses in the Northern Cape are the only known examples in Southern Africa. Approximately 136 of these South African houses remain. The structures represent a unique phase in South African vernacular architecture, yet many of the buildings have been lost as a result of neglect, damage from use as shepherds’ housing or livestock enclosures, theft of building materials, earth tremors, and modern resource extraction.
Hydraulic fracturing (fracking) applications are underway in the Northern Cape and the corbelled houses fall directly within the proposed fracking area. Earth tremors have already caused the collapse of several corbelled buildings and it is expected that additional tremors from fracking in close proximity will cause serious damage to the sites. The buildings are also threatened by modernization and loss of traditional knowledge. The art of corbelling is no longer practiced and as such many land owners are stabilising the houses with modern building materials and techniques. Buildings have been patched with cement or in some cases entire walls have been plastered to stabilize the structure. These non-traditional modifications are not approved by preservationists but with a lack of funding support by heritage authorities, land owners are resorting to changing the vernacular nature of the buildings rather than leaving them to collapse.
In order to digitally preserve the vernacular styles of the heritage sites, nine corbelled houses representing a range of styles and conditions were scanned. Data was collected with a Leica ScanStation C10 and a Z+F Imager 5010C. The corbelled houses project is additionally part of the larger CyArk 500 Challenge, which aims to digitally preserve 500 significant and/or at-risk cultural heritage sites around the world within 5 years. The scan data of the corbelled houses was used to assess damage to the structures.
Figure 2 shows a cross section of a corbelled house in very poor condition. Large cracks are visible on the outside of the house. Using the scan data, it was possible to show that the building is bulging by 60cm on one side. The bulging has put considerable strain on the walls and caused the structural cracks. The scan data also revealed that this shift in the walls has caused the wooden door frame to pull 15cm away from the building. As a result, the door frame is offering no support to the failing structure. Without any stabilizing reinforcements, this building is likely to collapse in time. Many of the already-collapsed corbelled houses in the Northern Cape have been lost due to similar unaddressed conditions.
Zaaylager Voortrekker Homestead
Built in 1853, the Zaaylager homestead is one of the oldest Voortrekker (early Dutch settler) houses in South Africa’s KwaZulu-Natal Province. The homestead is a rare example in which the outbuildings are still in existence (though they are in a poor state). On most historic Voortrekker farms, only the main house remains extant and the outbuildings such as the milk room, store room, carriage house and kitchen have long been destroyed, mostly due to neglect. The Zaaylager farm is also the location of the first battle where the Voortrekkers successfully defended their position against the Zulus and is associated with important Voortrekker leaders such as Gert Maritz. Although the building has been declared a National Heritage Site in South Africa, it has suffered from many years of neglect.
The farm is also bordered by a quarry mine. Subsequent vibrations resulting from the mine blasting have caused damage to the structures. Despite the significance of the homestead, the mining has been allowed to continue. The homestead’s foundations are also sinking, which is putting additional strain on the structure. As a result, water now collects around sections of the house, exacerbating the problems.
Figure 3 shows the main homestead and the carriage house as it was in 2010. Figure 4 was taken in 2014 and the rapid deterioration of the structure is evident. Some of the outbuilding walls have collapsed and one side of the main house is being held up with support beams to prevent/delay catastrophic loss of this significant piece of South African heritage.
The Zaaylager homestead was scanned using the Leica ScanStation C10 scanner. The final dataset consisted of 18 individual scans and a total of 170 million points, registered in Leica’s Cyclone software. The laser scan data offers an accurate digital record of this architecturally significant homestead which is already in a dire state. The scan data and processing software were used to assess the structural damage of the building. The reinforced wall was analyzed to determine the extent of its lean and the span of the major cracks (Figure 5). This information is crucial to establish whether the current beams can adequately retain the wall or if further support is required.
Conclusion
Vernacular architecture in South Africa faces numerous threats and many sites are highly degraded. Additionally, with ever-increasing demands on resources to support global population growth, organizations such as UNESCO are pushing for the study and re-instatement of traditional (vernacular) architectural practices. It is believed that vernacular architectural methods, having evolved directly from local conditions, are more sustainable and should at minimum be used to inform sustainable contemporary architecture. 3D laser scanning and other digital preservation methods are providing the tools to assess threats and damage to these structures. That information can be analysed to inform management and restoration plans, or to educate architects on sustainable construction techniques. In cases where there is a lack of resources to complete restoration, laser scanning provides a lasting digital record to serve as an accurate model for architectural research and cultural posterity.
Michelle Dye is a member of the Heritage Documentation Unit, a partnership between the African Conservation Trust and University of KwaZulu-Natal in South Africa. Dye’s background is in geography. She manages GIS and data processing for the African Conservation Trust, where she has been utilizing laser scanning since 2012. For more information contact michelle@ projectafrica.com or www.projectafrica.com.
A 3.399Mb PDF of this article as it appeared in the magazine complete with images is available by clicking HERE