Goggles on and black hair peppered with sawdust, French sculptor Vincent Mauger is intently studying the progression of his latest work, The Undercroft.

A new commission specifically for Fabrica, it is, ostensibly, a series of large shapes jigsaw-cut from oriented strand board (OSB) and slotted together. At once organic and architectural, its undulating peaks look, from the high vantage point of the gallery's pulpit, like a panoramic mountain range and from beneath, cave-like - somewhere goblins and trolls might hide. It manages to be simultaneously futuristic and rustic.

Vincent and partner Manon Tricoire have been working on it for several weeks. When I visit, it is part-finished, growing little by little by the hour. Vincent is drawing shapes freehand onto perspex and a team of helpers are then industriously cutting sheets of wood to his templates. Manon - who translates for her partner - says there is no blueprint. "He thinks about the general idea and then goes step by step, piece by piece. He works with a specific building system and then decides how the shape will progress."

Over the past year Vincent's work has been shown at galleries in Brussels, Paris and Nantes, but The Undercroft ("a cellar or underground room") marks the first solo UK exhibition for the 32-year-old, who comes from Nantes. Jonathan Swain coordinates Fabrica's summer exhibition, which last year saw Dominique De Beir create a "sparkly" site-specific construction of hole-punched cardboard boxes and fruit crates. He invited Vincent to create something for Fabrica after seeing works he had built in other former churches - from a "sea" of what look to be hundreds of balls of screwed-up paper to stacks of bricks that formed a church-within-a-church.

The Undercroft is a development of ideas presented in Vincent's untitled 2007 exhibition, in which he showed brightly coloured, interlocked geometric shapes and grey drainpipes cut and joined to form a topographical landscape.

"Every time, he is looking for a new way to work," Manon explains. "Every time, the materials and building system change."

Jonathan says: "At first sight, his formal concerns bring to mind the geometry of computer-aided design, but closer inspection reveals an artisan's pride in carefully crafted detail.

"His assemblages lie across the rather wayward creative path that starts with William Morris's Arts and Crafts movement, and ends in the rather fanatic excesses of an obsessive hobbyist."

As part of the exhibition, the gallery will be staging a series of talks and special events. These include an illumination of the structure, a series of evening acoustic sessions in which guests present audio interpretations of it, and a talk by Vincent himself.

For more information, visit the website at www.fabrica.org.uk.

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