Antrim House Roof Replacement Balances Heritage Integrity with Modern Performance

Antrim House is a Category 1 heritage building in Wellington, originally constructed in 1905 and designed by Thomas Turnbull and Sons as the family home of prominent businessman Robert Hannah. Since 1981, the building has served as the national office of Heritage New Zealand Pouhere Taonga.

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Addressing a Roof at the End of Its Service Life

The existing corrugated steel roof had last been replaced in the late 1960s, during a period when the building was used as a public service hostel. Over time, shortcomings in the original detailing, combined with natural material degradation, resulted in increasing maintenance demands and ongoing weathertightness concerns.

The replacement project provided an opportunity not only to renew the roofing material, but also to correct historic design weaknesses. Improvements were made to rainwater disposal capacity to better handle modern weather patterns and more intense localised rainfall. Structural changes within the roof and attic, along with the removal of three masonry chimneys, also contributed to improved seismic resilience.

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Addressing a Roof at the End of Its Service Life

The existing corrugated steel roof had last been replaced in the late 1960s, during a period when the building was used as a public service hostel. Over time, shortcomings in the original detailing, combined with natural material degradation, resulted in increasing maintenance demands and ongoing weathertightness concerns.

The replacement project provided an opportunity not only to renew the roofing material, but also to correct historic design weaknesses. Improvements were made to rainwater disposal capacity to better handle modern weather patterns and more intense localised rainfall. Structural changes within the roof and attic, along with the removal of three masonry chimneys, also contributed to improved seismic resilience.

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Selecting a Roofing Profile Appropriate for a Category 1 Heritage Building

For a building of this significance, visual authenticity was critical. Any new roofing system needed to closely match the original corrugation profile while delivering modern durability and low maintenance performance.

Roofing Industries’ True Oak long-run corrugate profile was selected to meet these requirements. Featuring deeper curves and distinctive shadowlines, True Oak replicates the appearance of traditional high-profile corrugate commonly used on early 20th century buildings. This makes it particularly well suited to heritage applications where standard modern corrugate profiles can appear visually flat or out of scale.

The roofing was manufactured in 0.90mm aluminium and finished in Colorcote Alumigard, specified in Gull Grey. This combination provided both the visual texture required for the building and superior long-term performance.

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Material Performance and Longevity

Colorcote Alumigard uses a marine-grade aluminium alloy substrate, offering excellent durability, corrosion resistance, and reduced maintenance requirements over the life of the roof. Compared with coated steel, aluminium provides improved drainage capacity and long-term resilience, particularly on complex heritage structures where access for future maintenance may be limited.

The Gull Grey finish complements the renewed exterior colour scheme, contributing to a lighter overall appearance while remaining sympathetic to the building’s historic character.

Installation and Project Completion

The roof replacement was completed by Classic Metal, with Naylor Love acting as the main contractor. Following installation, the exterior of Antrim House underwent repair and full repainting for the first time since its original construction in 1905.

The completed project successfully balances heritage stewardship with modern building performance, delivering a roof that is durable, low maintenance, and visually authentic.

A Heritage Outcome Built to Last

The new roofing system enhances the architectural integrity of Antrim House while ensuring it is better prepared for future environmental and structural demands. Through careful material selection and profile design, the project demonstrates how contemporary roofing solutions can be applied to heritage buildings without compromise.

Project Credits

• Main Contractor: Naylor Love
• Roofing Installer: Classic Metal
• Roofing Manufacturer: Roofing Industries Central
• Architects: R&D Architects
• Engineering Consultant: Dizhur Consulting
• Exterior Repair and Repainting: LT McGuinness and JPB Painting

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