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Domestic Extensions & Alterations
Chapel Fields, Hertfordshire
- Architect: Seth White Architects
- Project type: Single-storey rear extension and internal alterations
- Location: Chapel Fields, Wilstone, Tring, Hertfordshire
- Our role: Structural engineering
- Point of engagement: Put forward by the architect and instructed by the client
Project overview
This project involved replacing an existing conservatory with a modern single-storey extension featuring a striking 3m x 4m cantilevered glazing corner. Designed to enhance both aesthetics and sustainability, a green roof was incorporated, bringing additional structural considerations to the table.
Design process
- Managing the load of the green roof: Green roofs introduce extra weight compared to traditional roofing. We carefully designed the structure to limit deflections on the cantilever beams, ensuring the sliding doors remained fully operational throughout their lifespan.
- Spreading the load efficiently: To maintain stability and spread the load, we used steel spreader plates under the main knock-through beam bearing. This allowed both leaves of the existing masonry to distribute the load effectively, eliminating the need for additional steel columns and foundation strengthening reinforcements.
- Seamless design integration: The chosen cladding not only framed the extension beautifully but also provided the necessary depth to conceal the steelwork supporting the cantilever.
- Understanding the foundations: The estate, believed to be originally built on a former poultry farm, featured mixed foundations – trench fill and piled. Trial pit investigations confirmed the existing foundation was trench fill, enabling us to match it for the new extension, simplifying construction and reducing costs.
Why the green roof matters
Green roofs are more than an aesthetic choice; they contribute to energy efficiency, improve drainage, and enhance biodiversity. This project exemplifies how structural engineering can support sustainable architecture without compromising on design or functionality.
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