Case Study: Winchester Cathedral Presbytery Roof
H+R were approached to carry out a preliminary timber decay survey of the high presbytery vault roof at Winchester Cathedral as part of an application to the Heritage Lottery Fund. The aim of the survey was to identify damp and decay problems or relevant building defects. Some structural timber decay had occurred in the past which had been subject to remedial repair and there were some very minor areas of active timber decay infection.
H+R found that the lead dressing on the roof and the lead lining to the valley gutters was reaching the end of its life. These failings had led to damp penetration in the interior. Widespread historic woodworm and death watch beetle was found to be confined to the non-structural sapwood of timber elements, therefore, H+R concluded this had not caused any structural damage. H+R investigated the potential of future timber decay by taking deep moisture readings of timber elements. As the readings were well below the timber decay threshold of 22 per cent, H+R concluded that the conditions were not sufficient to support thriving wood boring insect infestations. However, some minor areas of timber decay was identified in the boards of the timber fan vaulting.
How we solved the problem
H+R recommended that the lead dressings on the roof and the lead linings on the gutter valley should be replaced to prevent further damp penetration. It was also recommended that an overflow gutter alarm system should be installed as part of the envisaged refurbishment. H+R concluded that only relatively limited allowance would need to be made for repair or replacement of boards forming the highly important vaulted ceiling due to the small areas of localized decay.