Prewetts Mill

Working predominantly on the external envelopes, surrounding landscape and common areas, t-sa were appointed to consider the renewal of the exterior facades and roof of an old flour mill and adjacent vacant office building. Alongside repair of the existing external fabric, an economical palette of materials was introduced to form a new façade with a civic presence at an important gateway to the town centre. Internally, t-sa defined the character and atmosphere of the spaces to support the client team's internal housing design.

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Re-use: Facade and Common Space

Prewetts Mill, Horsham 2019

Exploring what it is to give structures new purpose, t-sa have completed a façade and common space project in Horsham, West Sussex.

The client asked for a reimagined future for an old flour mill and office building set to create 59 new apartments. Awarded by invited competition, the commission was to design a façade for the conversion, to enhance the site through economic design and careful consideration of the public and shared spaces and to provide design direction to the apartment interiors.

The site is approached from the south over the River Arun and the north from the higher vantage point of the town centre. The site’s visibility and recognition changes seasonally, distant glimpses of its roofs are caught through trees. The mill sits proudly on a busy intersection with retail surroundings. The office building adjoined, with its imposing horizontal slabs and band glazing, sat at odds with the host mill.

A market town, Horsham town centre is characterised by the steep roofs and dormers (the Carfax, market square) and the London plane lined streets of 17th, 18th and 19th century housing. Nearby areas that were formerly industrious with numerous mills or occupied by artisan cottages, are now predominantly offices, large retail premises and mixed use developments.

To re-establish the structures in the townscape, a vertical rhythm was applied with a formal composition of openings and materiality, fracturing the overwhelming horizontality and association to the open plan function. Whilst retaining and re-using as much of the existing structure and material as possible, a new rigour was instilled through inserting a set number of window proportions and facade details. The new language of the façade and roof-scape characterises the residential purpose, evokes notable local characteristics and speaks simultaneously to a universal language of proportion and order.

A subtle and muted colour and material palette is employed. Tactility is emphasised through simplification by painting the existing brick, exposing the concrete banding, introducing larch cladding and subtle relief between planes. The integrity of the old flour mill façade is restored by removing the 1980s structural glazing and reinstating modest window proportions. Pre-treated timber cladding infills the large glazing bands, referencing intricate local detailing. Breaking the dominance of the cantilevers, wrap around balconies, Juliet balconies, expressed rainwater pipes and render details around larger windows bring tactile sensitivities – relating this building to its past and future.

t-sa were also asked to design the common areas, the spaces connecting the public realm with the private domain of the home. Often neglected, the client sought a distinctive design for these in-between spaces, showing the same spirit of generosity to the lobbies, staircases, corridors and connecting walkways. t-sa continued the language of verticality, rhythm and tactility to these spaces. A warmth and elegance is evoked through careful use of terrazzo tile and walnut joinery. A floor-scape marks journeys, thresholds and transition spaces and an awareness of the individual and the communal simultaneously. Horsham’s many open spaces and pedestrian routes have places to pause, sit and take in the environs. The same spirit was carried through to enrich the public realm of Prewetts Mill through planting, seating and lighting, which buffer the site’s edges with the river Arun and the surrounding streets.

Jennifer Frewen

Associate Director


t-sa Team: Takero Shimazaki, Jennifer Frewen, Haruka Nogami, Craig Mitchell, Siong Wang

Photographs Anton Gorlenko, Paolo Emilio Pisano, t-sa