Elizabeth Farm - Australia

Westox Cocoon Case Study

Elizabeth Farm is an historic estate located in Rosehill, a suburb of Sydney, New South Wales, Australia. Elizabeth Farm was the family home of wool pioneer, John and his wife Elizabeth Macarthur. The estate was commenced in 1793 on a slight hill overlooking the upper reaches of Parramatta River, 23 kilometres (14 mi) west of Sydney Cove.

The small, solid three-roomed brick cottage in the Australian Old Colonial style was transformed, by the late 1820s, into a smart country house, surrounded by 'pleasure grounds', orchards and almost 400 hectares (1,000 acres) of semi-cleared land. Enveloped within later extensions, the early cottage remains intact, making it Australia's oldest surviving European dwelling.

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The Problem

Elizabeth Farm. Circa. 1794 is Australia’s oldest European style building, where previous unrestrained salt contamination has caused substantial fabric loss and structural deterioration. Elizabeth Farm was the home of John and Elizabeth Macarthur and was operational from 1793.

The original house was built with bricks, rendered and marked with Ashlar blocking and the servants quarters and kitchen were built from Sydney sandstone. The sandstone walls were suffering from decay due to high salt contamination caused by rising damp and in some cases previous lateral water problems. Several attempts had been made over the years to try to arrest the problem with limited success. Sacrificial renders have been on the building for some years and have been helpful in holding back the rate of decay, as has the use of traditional type lime washes particularly in the basement area.

Elizabeth Farm Gallery

The Solution

The “Westox Cocoon” material was used on several of the bad walls after the removal of the sacrificial render or lime wash with the aim of reducing the salts to a “safe” level so sacrificial renders or traditional lime wash could be used with some longevity.

The Cocoon was applied in two applications, each application being left for two weeks before removal. Analysis was carried out to verify the transfer of salt from the wall to the Cocoon. The first set of samples was taken prior to application, the second set of samples taken two weeks after the first application. These samples also included a sample of the Cocoon material taken from over the drill site of the previous samples and the third set of samples taken after the removal of the second application, also including a sample of the Cocoon from over the drill site.

The Result

Because Elizabeth Farm was comparatively high in salt contamination, especially nitrates, it should prove as a good indicator for other properties where deterioration from salt contamination needs to be controlled by doing the minimum amount of work. The traditional lime wash used over the desalinated areas should, by there sacrificial nature, provide early warnings of when the salt levels have again reached a stage where there is enough contamination to cause further deterioration.

In theory, if it took 210 years for the salt contamination to reach the stage it was at, if all the salt was removed, it should take another 210 years to reach the same level, of course it would not be allowed to reach the same level when preventing further deterioration is as simple as two more applications of cocoon as and when any areas of exfoliation become visible.

An inspection of the areas of desalination carried out in the November 2002 work was made in February 2010 and the results are quite impressive, only one small area of salt contamination is visible in the laundry area where the sacrificial render was used and another on the outside wall of the servant’s quarters where the lime wash was used. All other areas including the basement had no visible signs of salt action; even the flag stones on the verandahs which were deteriorating at a very fast rate have no signs of exfoliation after the cocoon treatment. The former curator of Elizabeth farm Mr. Gary Crocket confirmed that the maintenance costs associated with lime washing and sacrificial renders had been reduced dramatically.