Project Case Study: – Baronda House, Removal of Asbestos Roofing, Re-Roofing and Associated Works Project No. 708
CLIENT: Office of Environment and Heritage
Address: Baronda House, Nelson Lake Road, Nelson Lagoon, Mimosa Rocks National Park, NSW
SCOPE OF WORK
The project scope of works involved removing the asbestos roof materials, decontaminating, appropriate disposal of the asbestos materials, re-roofing, timber work, structural beam/pole works and and can be summarised as below:
- Site Establishment
- Set-up scaffold access to roof
- Removal of asbestos roof materials, decontamination and safe disposal
- Inspection of roof timbers and identify any required repair work
- Installation of new metal roofing and roof plumbing, flashing, cappings, gutters and downpipes
- Timber and roof trim works including fascia, eaves lining boards, pergola members, sunshade battens, external wall cladding
- Structural repair of poles and beams, underground and above ground sections
- Rendering of the brick chimney
- Other miscellaneous works as required
- Site Clean-up, disestablishment and handover
Located on the far South Coast of NSW, Baronda House is an outstanding example of a Modern Movement architect designed project house. Built by a specially selected local builder in 1968, the design features many of the ideas of the era and benefited from owner David Yencken commissioning leading Melbourne architect Graeme Gunn. A modular design repeats in spiral half-module rises around a central brick core surrounding the chimney. The house takes advantage of its remote location and environment, enjoying views of the surrounding coast and lagoon and the use of local timber in its construction. The construction materials used were in keeping with the minimalist ideas fashionable at the time, using locally sourced and milled hardwood spotted gum timber, a central core of brickwork and the then contemporary asbestos containing super-six fibre cement roof sheeting. The building was donated by the owner to the NSW National Parks in 1979 and has state heritage significance due to its innovative design and aesthetics.
Murphy’s completed the works using materials in keeping with the originals used. As the roof sheeting was originally an asbestos cement material, this involved sourcing metal roof sheeting specially designed to match the appearance of the now prohibited asbestos products.
Safe Access – Working at Heights
Access was safely provided with full perimeter scaffolding erected by licenced scaffolders around the roof and to all work areas at heights. The scaffolding was inspected every 30 days by the scaffolder.
Removal of the Non-Friable Asbestos Roof Sheeting and Asbestos Containing Mastic from Building Joints.
The building roof consisted of asbestos containing corrugated Super Six sheeting, a popular material of the 1960’s, which was now reaching the end of its usable life. The mastic joints of the building were tested in a NATA laboratory from a hygienist sample and these were discovered to be containing asbestos material and so also required removal to free the building from the hazardous materials known to the client. Murphy’s notified SafeWork NSW of the intention to remove the non-friable asbestos materials and developed an Asbestos Removal Control Plan and task specific SWMS. The surrounding areas were protected with black plastic and a licenced asbestos assessor ran asbestos air monitoring samplers while the asbestos removal works took place. Murphy’s in-house asbestos removal crews used full PPE protection including type 5 disposable coveralls, disposable gloves and half-face cartridge respirators while removing the hazardous materials. At the completion of the asbestos removal work the licenced asbestos assessor scrutinised the whole site and after a thorough visual inspection certified clearance from the removed asbestos containing materials. The asbestos materials were wrapped in two layers of black 200-micron plastic and sealed with duct tape before disposal at the locally licenced Central Waste facility near Frogs Hollow, with waste dockets retained as proof of legal disposal.
Roof Replacement Works.
Given the aesthetic heritage qualities of Baronda House, the removal of the asbestos roof was problematic as asbestos is now recognised as a dangerous carcinogen and prohibited in manufactured products. Consequently, that fibre cement type of roof sheet is no longer made. The solution proposed by Murphy’s was to nominate a roof sheet of the same shaped profile. The project team selected Lysaght Custom Orb Accent 35 in 0.48mm Base Metal Thickness. This gives the appearance profile of Super Six sheeting while being made of metal hardy enough for the corrosive coastal environment of Baronda House. The roofing was fixed in place using Class 4 65mm roof zips. Murphy’s skilled roof plumbers completed the roof with 0.55BMT Lysaght Custom Orb flashings, 150mm half round Colorbond gutter and installed 100mm round metallic Aries hand finished downpipes.
The brick chimney at the centre of the building was re-bagged/rendered by Murphy’s.
The structural heart of Baronda House is a centre of brickwork containing the chimney and a surrounding skeleton of vertical supporting timber columns. These posts are of locally grown and milled Spotted Gum tree species. Due to the aging process of the timber and the local environment, the feet of these posts needed repair work. Murphy’s provided these repairs using Acrow props for temporary structural support while the feet of the timber posts were cut-out, replaced and new concrete footings built in-situ. The work was completed by renewing the metal bolts and stirrups holding the main structural horizontal timber beams and vertical timber columns together.
All carpentry work was completed by Murphy’s in-house trade carpenters. Carpentry and timber repair work included pergolas, eaves lining, exterior cladding and timber blanking plates. Murphy’s procured Blackbutt, Spotted Gum and Oregon timber materials in keeping with the existing design of the structure and made like-for-like replacements. The work was inspected and approved by the client’s heritage architect.
Murphy’s managed all the main trade work for the Baronda House project in-house with employee roofers, carpenters and asbestos removers. All works were completed with great care and under the supervision of Murphy’s site manager in order to maintain the standard of workmanship necessary to meet the requirements of the heritage architect and the aesthetic integrity of Baronda House. Inspection and Test Plans (ITP) were used to confirm materials were of the correct type and were correctly installed at each stage.
A site-specific management plan was developed by Murphy’s to manage the WHS and Quality Assurance processes for the project. A rigorous project level risk assessment was created and specified safety controls which fed into the training requirements, project site specific safe work method statements and the site-specific induction taken by all project personnel. This suite of documentation formalised the procedures for the project personnel and for the company to follow to fulfil the responsibilities of Principal Contractor for the site. The site manager played a key role in monitoring and continually reviewing site conditions and activities, leading weekly formal safety inspections and adjusting work methods where required.
The project had a positive overall impact on Baronda House and the immediately surrounding environment. The chief benefits were the removal of the deteriorating hazardous asbestos materials of the super six asbestos roof sheeting, asbestos containing mastic and their safe disposal at a licenced waste facility. The heritage aesthetics of the building were maintained through replacement with matching materials and the life of the structure extended.
Environmental management requirements were communicated to the work crews via inductions and work method statements. Overall environmental management was documented in a specially developed project construction Environmental Management Plan.
Benefits offered to Client during Project Works;
- Heritage values of the building maintained through sourcing of appropriate building materials and high-quality installation by Murphy’s own employees
- Material deliveries and access successfully made using the sole rural unmade track to the site using smaller delivery vehicles
- Murphy’s own full-time Sydney trade employees were based with temporary accommodation providers in the local area allowing more effective management of the project personnel than outsourcing
- Effective management and coordination between Murphy’s Baronda House site team near Tathra and Murphy’s head office in Redfern, over 400km away.
- In person periodic management meetings at key times with Murphy’s project management team at the Baronda House site near Tathra throughout the project with the client
- The work was completed with no incidents affecting the safety project personnel or harming the local environment.