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Library extension with timber-framed walls

Working details

This two-storey extension to a Tudor farmhouse contains an office and library on the ground floor and master bedroom suite on the first floor. The ground floor is sunk below ground level to align the first floor with the floor of the adjoining farmhouse while giving generous ceiling heights to the library and office. The library is glazed with large, storey-height sliding windows and the walls are lined with bookcases made of oak-veneered ply, which are set within the depth of the walls. The windows lie flush with the inner face of the wall to align with the face of the bookcases. The resultant deep overhang shades the south-facing glazing.

The structure of the extension is a modern, environmentally conscious version of the timber frame. The walls are formed of storey-height prefabricated panels of timber - a 200mm timber stud framework with 12mm Panelvent breathable external sheathing on the outside face. The panels were assembled on site, and Warmcell breathable insulation was damp-sprayed between the studs before the internal wall lining board was fixed. The sheathing is lined with a breather membrane and clad with a rainscreen of board-on-board vertical oak boards. They are fixed to battens with their top edges cut at an angle to drain rainwater away from the sheathing. The boards are 25mm thick and dished slightly to give each a distinctive profile.

On the ground floor, the timber wall panels are fixed through a waterproof membrane to a waterproof concrete upstand.The window lintel is formed of a glulam beam, which projects over the corner as a cantilever to support the first-floor prefabricated wall panels.

The floor is paved with Portland stone and has an underfloor heating system.

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