A prefabricated modular unit on North Stradbroke Island has taken out the prestigious Australian House of the Year award for 2025.

Blok Three Sisters by Blok Modular and Vokes and Peters is a set of three coastal terrace homes designed for three sisters who grew up spending their childhood holidays on the same site.

In their submission, the designers said the brief was to create a dwelling that would allow the sisters to continue to holiday alongside each other with their own families.

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"This meant each must be the same and have equal access to the beach. We needed to bring light and air and amenity into the centre of a skinny floor plan especially for this middle unit."

Prefabricated in the Blok Modular factory in Brisbane, the parts were then assembled on the island to increase efficiency and ease building costs.

An example of "stealth density", three houses have now been placed on the one site in what was considered sustainable and responsible residential design.

"This project sets a benchmark for lightweight, medium-density housing on the island, providing an adaptable and resilient solution to environmental changes/challenges," said the designers.

Launched in 2010, the Awards celebrate projects across 10 categories, including New House (under and over 200 square metres), House Alteration and Addition (under and over 200 square metres), Apartment or Unit, Sustainability, House in a Heritage Context, Emerging Architecture Practice, Australian House of the Year, and the newly created Small Project.

The Small Project award was introduced to recognise innovation and impact in small builds and the inaugural winner was Window, Window, Window by Panov Scott.

The project is a granny flat that is seamlessly inserted in the underneath space of an existing house, creating a functional second dwelling.

In a statement the jury said this project was "an exemplary secondary dwelling that employs clever siting and efficient planning without sacrifice to a rich interior setting."

Winner of the New House Over 200 Square Metres went to Studio Bright for its Hedge and Arbour House - a vine-covered Melbourne home where architecture dissolves into the site.

Sawmill Treehouse, a tiny cabin suspended among the gum trees, took out the win for New House Under 200 Square Metres.

With sustainability a very real concern for design studios, the winner of the Sustainability award - Cake House by Alexander Symes Architect - was considered to be a fantastic blueprint for a sustainable beach house that could be used elsewhere in Australia.

The renovated beach shack accommodates 17 guests and features passive house principles combined with high-performance, climate-resilient design.

This year's esteemed panel of jurors included John Ellway from John Ellway Architect, Polly Harbison, principal of Polly Harbison Design, Dimmity Walker, director of Spaceagency Architects and John Wardle, founder of Wardle.

They were joined by jury chair Alexa Kempton, editor of Houses magazine and Architecture Media, as well as Louise Honman as the heritage advisor and Pippa Soccio as the sustainability advisor.

In a statement, Kempton said the winners responded to their briefs and site with "skill and inventiveness" to achieve "elegantly resolved designs for welcoming, livable homes."

"Across multiple category winners, designs resolved this need for adaptable domestic space with a commitment to quality over quantity," she said. "These are homes without excess, with designs that optimise living environments to the last millimetre."

"The jury was encouraged by the replicable strategies demonstrated in the winning homes, and would be delighted to see such ideas proliferate in our neighbourhoods."

The complete list of winners

Australian House of the Year - Blok Three Sisters by Blok Modular with Vokes and Peters (QLD)

New House Under 200 Square Metres - Sawmill Treehouse by Robbie Walker (VIC)

New House Over 200 Square Metres - Hedge and Arbour House by Studio Bright (VIC)

House Alteration and Addition Under 200 Square Metres - Carlton Cottage by Lovell Burton Architecture (VIC)

House Alteration and Addition Over 200 Square Metres - Cloaked House by Trias (NSW)

Apartment or Unit - Blok Three Sisters by Blok Modular with Vokes and Peters (QLD)

Small Project (new category) - Window, Window, Window by Panov Scott (NSW)

Sustainability - Cake House by Alexander Symes Architect (NSW)

House in a Heritage Context - Mess Hall by Architecture Architecture (VIC)

Emerging Architecture Practice - Ellul Architecture