Cantilevered terrace marks out Gillespie Yunnie’s extension to house on Dartmoor

We were asked to refurbish and extend a 20th-century house in Ashburton on the south-western edge of Dartmoor. The project included replanning interiors, adding a contemporary living-space extension, and significantly improving thermal performance and energy efficiency. The completed work features a new roof structure, a dynamic first-floor extension with a cantilevered terrace, and an insulated render system, achieving excellent air tightness and incorporating renewable energy sources. Specific requirements included maximising views of Dartmoor, ensuring privacy at night, and creating functional, contemporary family spaces.

Can you describe how you treated the exterior?

The external treatment includes an insulated render system over the existing structure, new triple-glazed windows within existing openings, and highly insulated new roofs. The composition is clean and modern to elevate the existing house, with a focus on enhancing energy efficiency and visual appeal. The construction involved significant fabric upgrades and the integration of renewable energy sources.

How did you approach the interiors?

We designed the interiors with a clean, simple aesthetic, using a soft natural palette. Functional family spaces were created, and the layout was reformatted to maximise views of Dartmoor while providing an open-plan, contemporary living space connected to the surrounding landscape. Floor-to-ceiling glazing in the new extension allows natural light to penetrate deep into the interior, while soft linen curtains address privacy and light spill concerns.

What was your approach to sustainability?

The project prioritises sustainability with enhanced thermal performance, excellent air tightness, and renewable energy sources. Triple-glazed windows, highly insulated roofs, photovoltaics and a large air-source heat pump contribute to the house’s energy efficiency, reducing the client's monthly energy bill to just £6 during July last year.

What was the main challenge and how did you overcome it?  

Integrating modern energy-efficient features within the constraints of the existing 20th-century structure and Dartmoor National Park’s planning requirements was a challenge. We overcame this through design solutions such as insulated render systems, triple glazing, and renewable energy installations while respecting the park’s ‘dark skies’ policy by using low emissive glazing where possible.

What is your favourite detail in the project?  

Our favourite detail is the first-floor extension and cantilevered terrace, with stick balustrade and timber fins. The terrace offers stunning panoramic views of Dartmoor while improving the living experience by connecting indoor spaces to a floating terrace within the tree tops.

Are there lessons from this project that might be applied elsewhere?

This project demonstrates the importance of integrating modern energy-efficient features within existing structures, emphasising thermal performance and renewable energy. The use of these can be applied to similar retrofits. Additionally, the focus on maximising natural light and views, while addressing privacy and light spill concerns, highlights a balanced approach to contemporary living needs. These principles can guide future projects in enhancing both sustainability and occupant comfort.

Philip Yunnie is a co-founder of Gillespie Yunnie Architects

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Key data:
Total contract cost Undisclosed
Area of extension 242m²