Cloaked House was a test of precision, sequencing, and trust. Perched on a steep, land-slip-prone site in Mosman, the project involved retaining and remediating the existing mid-century structure while excavating a new basement beneath it, all without compromising its integrity. From stabilising the hillside to removing asbestos and treating concrete cancer, early works were carried out with care and foresight.
A new insulated timber skin was wrapped around the original blockwork, dramatically improving passive performance without the need to demolish and rebuild. Structural steel was retained, stitched into, and extended with timber and recycled Australian hardwoods, allowing for new services and high-performance glazing. Much of the home was built from within, requiring close coordination, careful access planning, and a collaborative approach from every trade.
Rather than starting over, we enhanced what was already there, extending the life, performance, and story of an existing home. This is what we mean by craftsmanship and care.
Extensive Structural Remediation, Renovation & Landscaping
Trias
SDA Structure
Clinton Weaver
Open riser staircase in the central courtyard.
The handing pendent lights and ceiling rafters pay homage to the original design of the home.
Polished concrete floors in the downstairs living room.
Large solid entry door.
Redesign of the timber and steel balconies.
Australian hardwood joinery and green tiles that give reference to the midcentry era of the home.
Curved sheer curtain to seperate the entry and upstairs living.
Recycled timber floorboards.
Eastern elevation of the balconies with Abodo stained timber cladding.
Sliding doors pull back to connect the balconies to internal areas.
Openings are enlarged for light, air and view.
Full view of the rear of the home.
Recycled mosaic tiles and square cabinets call back to the homes original design.
“Arc. took our documentation and design intent and realised it with great skill. They supplemented our knowledge where it was needed and developed positive working relationships with our clients, a complex suite of neighbours, and our consultant team.”
Our Impact
Built to Last
Much of the existing building was retained, including slabs, perimeter walls, and structural steel reducing waste and preserving embodied carbon. The existing structure was meticulously reinforced then cloaked in a thermally modified cladding that allows for an additional layer of insulation.
Reuse with Intention
Salvaged and recycled materials played a major role. Sandstone cut from the new basement rooms were used throughout the landscape. The old rafters were remilled to become joinery pieces, furniture and outdoor benches. All the doors and windows were made using timber reclaimed from houses in the Illawarra.
Comfort and Performance
The rebuilt envelope introduced insulation and thermal upgrades while working within the retained structure. Double glazing, cross ventilation, and passive heating strategies helped reduce energy use. All-electric systems were supported by a 13.2kW solar array, hydronic heating, and in ceiling cooling panels.
Working With the Landscape
Site works were carefully managed and stablised to avoid disturbing the surrounding land and vegetation. Native plantings were introduced to enrich biodiversity, while mature trees and existing topography were protected respected throughout.
Our Process
Pre-Construction
In addition to progressive preliminary pricing, pre-construction focused on understanding the existing structure, determining how best to remove, retain, reinforce, and support it. Key trades were brought in early to ensure the build was achievable on a steep, land-slip-prone site. We worked closely with the architect and engineer to cost design options, refine sequencing, and value manage key packages, aligning architectural outcomes with program, access, and budget realities.
Original Photo taken in 1960.
Initial design model by Trias.
Early Works
Early works were extensive; stabilising the land, remediating the structure, and preparing for excavation beneath the existing house. Works included piling, shotcrete, and major earthworks through sandstone to carve out a new basement. Tree protection, asbestos removal, and treatment of concrete cancer were undertaken with care, alongside the safe removal of original balconies and other compromised elements.
Shotcrete Stabilisation to retain the existing site conditions
Subterranean Rock Excavation a complex operation demanding careful sequencing and structural oversight.
Structure
The existing structural skeleton slabs steel and perimeter blockwork was retained and remediated, becoming the backbone for the new works. Careful propping and sequencing allowed us to insert new framing and infill without disturbing the structure’s integrity. Timber was used strategically to introduce warmth, lighten loads, and ensure buildability on a constrained site. Much of the new work was stitched directly into the old requiring high precision and close coordination between trades.
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Temporary Void during temporary propping and infilling of perimeter walls
Structural Timber posts extended three floors high supporting all the balconies, balustrades and roof.
Enclosure
A new timber-framed skin was built around the existing block structure, allowing for insulation to be installed continuously across the facade. This was then wrapped in high-performance membranes, tapes, and flashings to ensure airtightness and elevate passive performance. The cladding is rapid growth and thermally modified timber. Doors, windows, and ventilation hatches all double-glazed and made from recycled Australian hardwoods punctuate the enclosure with precision.
Insulated Timber Skin installed between new timber framing over the original blockwork, forming a continuous thermal envelope beneath the cladding.
Recycled Hardwood Joinery integrated into the Abodo cladding with operable hatches and windows for ventilation, shading, and performance.
Interiors
The interior fitout was carefully coordinated to ensure performance, durability, and visual clarity. Heating and cooling systems were integrated early, with in-slab hydronic heating to the ground floor and concealed ceiling systems above, delivering year-round comfort without compromise. Services and plant were planned from the outset to be fully concealed, allowing for clean detailing and reduced visual clutter.
Solid timber floors and custom spotted gum joinery provide warmth and longevity. All finishes were executed with minimal trims, no skirtings or architraves, demanding zero tolerance and exact setouts. Tiling was planned in coordination with cabinetry and structure to ensure alignment. External elements like wire balustrades, brick paving, and recycled hardwood were carried inside to maintain consistency and quality throughout the home.
Precision Execution steel, timber and block work coming together around the central atrium.
Kitchen tiles micro adjustment to joinery and structure to ensure a full tile bench and splashback.
Aftercare
We've remained actively involved through seasonal and on-demand aftercare, from routine timber oiling, tile sealing, and repainting to coordinating services and trades. We’ve ensured fittings remain sound, systems operate smoothly, and the home continues to perform as intended. Our knowledge of the build allows us to provide fast, efficient care when needed, even as the home evolves.
We’ve also supported the clients in upgrading and expanding the house post-handover, providing trusted assistance for everything from new fixtures to EV infrastructure and a proposed pool addition ensuring continuity, care, and craftsmanship beyond completion.
Recycled Timber benches made with the old rafters form the seating for the Western terrace.
Routine timber oiling on north facing balcony.
Recognition
Awards
Publications
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