Stabilising the stone archway at Vaucluse House

A team of specialists undertook a delicate and complicated operation to rescue a significant 1830s stone archway from an invasive climbing plant.

Vaucluse House is one of the few 19th-century houses on Sydney Harbour that have retained a significant part of their original estate setting. A distinguishing characteristic of the 19th‑century estate is its careful division into specific areas, both functional and ornamental, such as the kitchen garden, stables and rear service yard, paddocks, carriageway, pleasure garden, creek, estate backdrop, and beach paddock.

When William Charles Wentworth purchased the property in 1827, Vaucluse House was a small cottage. Over the next five decades, William and his wife, Sarah, extended the cottage into a magnificent villa, set in a large and picturesque estate.

The aesthetic significance of Vaucluse House and its outbuildings is embodied in the substantial use of locally quarried sandstone. Another noteworthy feature is the use of delicate castiron posts and tracery valance on the verandah, in contrast with the heavy battlemented parapet on the house itself. Together, these exhibit the attributes of the Old Colonial Gothick Picturesque style, also known as Colonial Gothic Revival.

Signs of decay

With areas of the external stonework and metalwork on Vaucluse House and its outbuildings showing signs of decay and corrosion, in 2018 Sydney Living Museums (now Museums of History NSW)conducted a comprehensive condition survey. We then developed a conservation strategy prioritising the areas most in need of conservation and repair. The first area identified was the 1830s elliptical stone archway leading to the courtyard, and the adjacent wall. These were structurally compromised by the deeply embedded root system of a Ficus pumila (climbing ficus) that had displaced some stone blocks.

Due to the complexity of the works and the types of material requiring conservation, an interdisciplinary team of specialists was established to scope and undertake the works. The team included a heritage architect, an engineer, material specialists, heritage stonemasons, and our Heritage and Horticulture teams. Before works began, detailed measured drawings were prepared of the area to map the condition of the heritage fabric and its built details.

An invasive climber

Although many climbing plants are non-invasive and pose no threat to masonry walls, the mature climbing ficus had become deeply rooted in the stone joints of the archway and adjacent wall, causing irreversible damage and compromising their structural integrity. Large and fine fibrous roots were embedded in the joints, accelerating the loss of mortar, particularly around the keystone, voussoirs (the wedge-shaped stones that create an arch) and the parapet blocks. The Heritage team determined that the only effective treatment of this well-established ficus was its complete removal by dismantling the elliptical archway and stone wall to eradicate all roots.

First, the Horticulture team removed the climbing ficus from the surface of the stonework. The timber gate was then detached from the four iron pintiles (hinges) in the archway in order that a full damage assessment could be completed. So the archway could be safely dismantled, the stonemasons constructed a temporary timber falsework to take the load of the stone blocks. Before dismantling, each block was tagged with a unique number annotated on the measured drawing to ensure it was later reinstated in the correct position.

As the archway was being dismantled down to its base stones, the four iron pintiles, embedded in poured lead in the archway blockwork, were retrieved and partly reconstructed by the metal conservator using stainless-steel shanks, or tangs. The original iron tangs had corroded and expanded, causing cracks in the stones.

Conserving the original fabric

With the stone blocks numbered and laid out for detailed assessment and inspection, it was determined that the two cracked stones that support the upper pintiles needed to be pinned together using stainless-steel dowels. The two stones supporting the lower pintiles were pinned back to the parent stone in situ.

Holes were drilled into the stone sections, dowels were cut to length and everything was dry‑assembled to check for a good fit. The holes in both sections were then filled with adhesive, the dowel fitted into one section, and the break surfaces covered with a fine colour-matched mortar. The joint was then immediately assembled, and any excess mortar cleaned away.

Our conservation approach is to maintain the authenticity and integrity of our properties. Therefore, where some stones showed signs of delamination, or separation into layers, rather than remove the lamination, discrete lime mortar fillets were applied to the edges of the laminations to extend the life of the original stone surface. Only one badly fractured stone had to be replaced in the rebuilding of the archway, which was completed in December 2018.

The next area identified for conservation work is the 1830s flagstones on the verandah, where the corroding bases of the cast-iron posts have expanded, damaging the surrounding stone flags. These are just two of the many complex and significant conservation works in train at our properties.

Contractors

• Nicola Ashurst, Adriel Consultancy, heritage architect and material specialist
• Ken Ellis, Artisan of Stone, heritage stonemason
• Eamonn Madden, Partridge, structural engineer
• David McBeath, OHM Consultants, material specialist