Waterside House Extension, West Sussex, England

Waterside House Extension in West Sussex, UK

3 November 2026

Design: MortonScarr Architects

Location: West Sussex, south east England, UK

Photos: James French

Waterside Extension is a beautifully completed residential project nestled in the picturesque locale of Ashington, Pulborough, West Sussex, UK.

This distinctive development, completed in 2025, represents a thoughtful and harmonious expansion of an existing former barn, transforming it into a contemporary and highly functional kitchen and dining space. The primary aim of this architectural endeavour was to seamlessly integrate a new, open-plan extension with the surrounding garden and natural spring that runs through the site.

Spanning a generous project size of 120 square metres on an expansive 500 square metre site, the project is characterised by its single-level design, ensuring both accessibility and a harmonious connection with its natural surroundings through the use of full height sliding windows, one of which retracts into the external wall to leave a column-free open corner.

The design ethos behind this residential addition focused intensely on creating bright, inviting interiors that maximize natural light and offer a modern, sophisticated aesthetic, all while subtly referencing and respecting the unique heritage of the original barn structure.

This careful balance of traditional elements and contemporary design results in a truly unique and engaging living environment. The newly formed open-plan layout significantly enhances the physical and visual connection with the surrounding garden, providing an ideal setting for both everyday life and entertaining.

Located in West Sussex, UK, what unique site conditions or local contextual factors influenced the design and material choices for the extension? How does the project respond to its specific environment?

The extension was positioned on the northern elevation of an existing converted barn, adjacent to a natural spring which runs through the site and against a garden wall with the neighbouring property. The existing barn was constructed from a mixture of brick and flint, and features 3 large buttresses to the northern elevation, perhaps constructed to avoid subsidence caused by the adjacent water.

The concept for the design of the extension was to introduce a large amount of glass, to allow morning light to fill the space, as well as indirect light through the course of the day. Two sets of sliding windows address the corner of the extension, which is column free due to a cantilevered beam that spans over the entire corner of the structure. This allows the windows to slide back – in one case into a pocket within the external wall – and reveal the verdant garden and springs beyond.

The canopy roof, finished with a natural clay plaster, is tapered in elevation, to reference the adjacent sloping buttress structures. The walls of the extension are clad using a black board and batten system, to contrast against the adjacent red brick.