Design Considerations 6.1 Roofing Elements In roof replacement, faithful replication should be the first option to be considered. Where not possible, due to unavailability or budget constraints, materials with similar visual characteristics and performance should be chosen. Where the appropriate material is no longer in production, it may be possible to substitute from another less visible part of the building or to source from a reputable architectural salvage company. With stone, slate or old tile roofs, all visible pitches should retain the original finish. Substitute materials should be chosen with care as modern equivalents may be heavier than the original covering. Roof structures may only have been designed to carry the weight of the original material, and major problems can be caused with the substitution, for example, of slate by concrete roofing tiles.
Heritage: Care and Development Strategic Planning NR/GN/CIV/100/05 July 2020 67/130
Whenever undertaking works to existing buildings, earlier and inappropriate repairs should be rectified. This should include the removal of crude ‘emergency’ repairs such as ‘Turnerising’ or ‘Flashband’ where they disfigure the appearance of the building. Repairs should never be undertaken by covering existing tiles or slate with bitumen or other substances that may prevent their eventual reuse. This does not mean that temporary repairs cannot be carried out when they are essential to stop water penetration and worse damage occurring while a more permanent solution is being organised. In these circumstances, the choice of methods should be limited to those that are quickly reversible without damage the fabric of the building.
There are, however, exceptions and slates have been known to be replaced by clay pan-tiles in cases where it was confirmed that these were the original material. The priority should always be to prevent water ingress and a change of material and detailing may sometimes be the better solution.
Image 6.4 Rainwater goods — replacement lead hopper and downpipe, reproduced in style of original at Bishopstone station, Grade II listed