Fonmon, built by the St. John family and listed Grade 1, is one of the few medieval castles still lived in as a home. The rectangular keep was built c.1200 and is still the core of the castle, although most of the present building dates from the postmedieval period: the Georgian interiors are exceptional.

Small cracks in the ornate plasterwork suggested potential problems, though gave little hint of the repairs ultimately required. The integrity of the timber roof structure over had been severely compromised through rot and water penetration, significant replacement of the existing structure consequently being required. This replacement had also to be carried out whilst ensuring the existing ceilings remained undamaged and insitu.

The investigation, diagnosis and repair typifies the services provided by DSA to conserve our heritage, repair always being preferred to replacement wherever possible.