Within a conservation area, the Watercress Cottage is a grade II-listed cottage next to the Farleigh Hungerford Castle ruins which are visible from the cottage's patio.
Connected to both the kitchen and main living room, the 33-square-metre extension adds an additional bright living and dining space to the historic cottage.
"Watercress cottage demonstrates that it is possible to extend a historic building in a way that respects it whilst making a positive contemporary architectural statement, the result of which is a new life for the building with amazing views," said Greenaway Architecture.
"The design is an architectural expression which is both bold enough to demonstrate the commitment to quality and modernity and modest enough to sit happily in the historical setting."
With three walls built from glass, the extended space opened up the cottage's northwest wall, which brought more light and better views of the surrounding countryside and spring-fed pond.
The extension was built from a thin steel frame with glass-to-glass corners to give almost unbroken views to the pond.
The studio opted for a sedum roof to help trap warmth inside the extension and enrich the biodiversity of the environment. Rain chains instead of gutters were used to drain rainwater from the roof.
With the aim of creating a warm and energy-efficient space, the walls were constructed with high-performance double glazed panes.
With studios in London, Hampshire and the Cotswolds, Greenaway Architecture was founded in 2015 by Duncan Greenaway.
Other recent extensions on Dezeen that were designed to extend and modernise historic buildings include a glazed extension to a Victorian villa in Edinburgh and a timber extension to a cottage in Devon.
The photography is courtesy of Greenaway Architecture.