THE ARCHITECT / RETROSPECTIVE
Dumas House Conservation The Dumas House conservation was a large scale exercise in the conservation of a mid-twentieth century building which provided some valuable lessons for future conservation of buildings of the period.
WORDS AND PHOTOGRAPHY: PHIL GRIFFITHS
Dumas House was the result of a desire for government to focus a large part of their civil service in one location and a subsequent design competition won by then government employees Finn, van Mens and Maidment. Of the five towers that were planned at the time only Government Offices, later renamed Dumas House, was built. It opened in March 1966 and originally housed the Public Works Department, who moved from the Barracks and a number of other locations around the city. The building was steel framed with fire protection, concrete protection to the exterior, built up membrane roofs, precast concrete spandrel panels, faience block panels to the ends of the building, terrazzo cladding to columns and Tyrolean soffits. A number of failures were exhibited over time which led to its conservation, the most dramatic of which was detaching sections of spandrel panel, giving rise to parts as large as 3 kgs falling a number of floors. Prompted by the more obvious failures, a more detailed investigation was undertaken of the building envelope with the overriding aim to have a conservation outcome and a building that would be stabilised for a further 50 years.
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Investigations revealed building defects that arose from a combination of factors including design, changes to design during construction, poor construction practice and materials reaching the end of their design life in the case of waterproof membranes. Remediation was undertaken off mast climber platforms that were moved sequentially around the building. The precast spandrel panels were designed as stainless steel reinforced monolithic exposed aggregate elements. In fact, they were made with unprotected steel reinforcement, a very thin layer of concrete protection and an applied exposed aggregate finish. Inadequate cover caused carbonation and there was failure of the panel aggregate surface and of the concrete itself. The simple solution was to remove all of the failing panels and replace them with panels made to the original specification with Xpex added to improve water proofing qualities, which took some time to achieve to ensure the quality of the finish. A new levelling and fixing system was devised to achieve a more positive fixing system. Concrete repairs were also required in preparation for loading up the new panels.
RETROSPECTIVE / DUMAS HOUSE RESTORATION
