18 C O N T E X T 1 1 3 : M A R C H 2 0 1 0 Mike Coull is on secondment from Grampian Fire and Rescue Service to Historic Scotland, where he is the lead officer on the Scottish Historic Buildings National Fire Database project and heritage coordinator for the eight Scottish fire and rescue services. As a result of past and current research, there is now a better understanding of the actual performance of doors in fire. This permits a more realistic assessment of historic doors in these situations, leading to solutions that can keep them in place. There are a number of techniques that can be employed to improve the fire resistance of a door. These include: • facing the door with non-combustible boards, which can be removed at a later date with minimum damage • sealing all cracks and gaps with an intumescent paste, and applying coats of intumescent paper, varnish or paint • fitting proprietary intumescent strips and flexible cold smoke seals, to seal the gap between the door and frame. In the selection of upgrading treatments, the effect to the character of the door must be weighed up against the heritage value. Doors often vary within a single property, and greater intervention to the inner face of plainer doors in upstairs rooms may be feasible. A couple of current projects are aimed at addressing the needless removal of historic doors. In 2006, a project led by TreSenteret of Trondheim, Norway was proposed. The goal of the project is to provide a unique new e-tool to predict fire behaviour of timber doorsets in situ, against detailed specification (door characteristics and function). This reduces the need for destructive testing of historic doors. Historic Left: Smoke penetrating joints at the perimeter of panels Right: A panel burning through Scotland, English Heritage and the National Trust are all partners in this project, recognising the benefits that such a tool would deliver. In March 2009, the technical conservation group of Historic Scotland undertook a small testing programme to assess the fire performance of traditionally constructed Scottish doors. The doors were not ‘high-end’ doors such as hardwood doors in a stately home, but the types of doors endemic in traditionally constructed homes across Scotland. The doors were recycled and were all four-panelled, made from soft wood, and of mortice-and- tenon construction. Six doors were subjected to rigorous furnace tests, to BS 476, part 22, 1987; one was left untreated; and the remaining doors were upgraded by varying degrees, including with intumescent varnish and paint, and non-combustible boards. The results are currently being analysed. The findings will be published on the Historic Scotland website in mid-2010. Test certificates or compliance with published standards of construction are frequently required by local authorities. Testing for guaranteed performance is to BS 476, part 22. This is an acceptable process for new prototypes, but obviously a highly destructive process for existing doors. In many cases, an independent assessment by a recognised fire safety consultant, taking a holistic view of the building and in the context of other fire precaution measures, may lead to more sympathetic solutions which will be acceptable to the local authority.
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