CONTEXT 178 : DECEMBER 2023 27 BUILDINGS IN THE COUNTRYSIDE there are incremental changes. Failures such as decayed groundsills, beam ends encased in damp masonry, and deep splits on the external face of timbers require a number of approaches to remedy and address the cause, as moisture contents persistently at 20 per cent and higher can allow wood-destroying organisms to infect the timber. Whatever the scale of the problem, addressing the cause of the moisture ingress is required, so that the timber is as isolated as possible from excessive moisture and as ventilated as practicable. Mitigating the environment to enable the timber to have a lower moisture content is the over-riding intention. Additional interventions such as repairing, replicating, reinforcing or substituting with another material are all potential options to be evaluated. Similarly, it may be that a new structural pathway could be introduced to circumvent the failed element and allow it to be retained as is. An example is the use of plywood sheets fixed to the external wall and roof frames to create a diaphragm structure providing improved racking resistance. Timber-framed structures have a unique characteristic compared to the other vernacular building materials such as earth, stone or brick, in that they are prefabricated. A kit of parts that can be easily assembled can also be disassembled, conserved and then reassembled. While this is not a default option, in particular circumstances dismantling either partially or completely offers a least-worst option. The interventions to the timber can be very well focused and allow more timber to be retained than if carried out in situ. All of these potential interventions can be evaluated against their potential impact on the significance of the timber structure. In doing so the options that cause the least harm, address the causes, and maintain this significance can be identified. This allows a specification for the conservation work to be agreed, and justified and defended, on this basis. This will answer to the question: ‘what is the best approach, and why?’ Ideally it is the responsibility of the decision makers, those commissioning and compiling the plan, to be clear and transparent about the choices they have made, and to demonstrate that they have minimised harm and maintained or, if appropriate, enhanced significance. The alternative is that little or minimal discussion or evaluation are provided, and a solution is proposed in relative isolation which often causes avoidable harm, costs more and takes longer. Few projects are able to combine the qualities of legibility, re-treatability, maximum retention, minimum intervention and like-with-like, to a high degree. It is this task of negotiating the optimum blend, based on reliable and up-to-date information and understanding of the value and potential impacts that is both exciting and challenging, and reminds us of the importance of context and a conservation plan. Joe Thompson, the programme leader of the timber building conservation MSc and carpenter-inresidence at the Weald and Downland Living Museum. He has been conserving timber structures for more than 30 years. A timber floor beam decayed at its end and supported by a wrought-iron beam The labelled offcuts from the repair of an 18th-century cottage, aiming for maximum retention
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