24 CONTEXT 178 : DECEMBER 2023 There could be as many as 60 courses, so it is easy to get lost between them. The solution is to photograph every course with the slating raked back and including scales. Mistakes can then be checked later, and if the slating has slipped it can be Photoshopped back to its original position. Better still for the most complex details, such as some valleys, is to video the whole process so that the stripping can be viewed repeatedly. Each part of the roof should be examined in turn. Do the eaves include a wall plate and tilting fillet to raise the slating, or do the rafters foot on to the wall head, with the eaves slating having two short under-eaves slates to make it level and provide tilt? How are verge and top course slates fixed? They may rely on mortar to make them secure, sometimes without pegs or nails. Abutments probably will not include lead soakers or flashing, but is the slating slightly tilted by packing up the laths, or over a raised rafter to direct water away from the vulnerable joint? Is the mortar flaunching protected with listings? How are hips and ridges detailed? Most of all, any valleys need careful recording, understanding and accurate description. There are many types, some restricted to quite small geographical areas. Recent work in north Wales has revealed four valley types within a 30-mile radius: single cut, shale, Welsh open, and Welsh close-mitred. None relies on lead, and some were devised to cope with the very small and narrow, local slates. Inevitably, the survey will throw up questions and options for repairs or renewal. Currently the building standards are the main source of guidance but, as explained, they are not ideal. More appropriate guidance is available from the national conservation bodies. Historic England’s Practical Building Conservation: Roofing1 is excellent on roof detailing, and its Stone Slate Roofing Technical Advice Note² (English Heritage) is being revised to include metamorphic slates. A Code of Practice for Slate and Stone Roof Repair and Conservation is in draft. English Heritage’s research on stoneroofing is available as a free download³. More generally, The Pattern of Traditional Roofing⁴ by Gerald Emerton describes the evolution of slating and tiling. References 1 Historic England (2014) Practical Building Conservation: Roofing, Routledge Taylor and Francis Group, Oxon. https:// historicengland.org. uk/images-books/ publications/roofingconservation/ ² Historic England (2005) Stone Slate Roofing: Technical Advice Note. https:// historicengland. org.uk/imagesbooks/publications/ stone-slate-roofingtechnical-advice-note/ stoneslate/ ³ English Heritage (2003) Stone Roofing. https://tinyurl. com/32u44zs7 ⁴ Emerton, G. (2018) The Pattern of Traditional Roofing, Glebe House, Acton, Nantwich CW5 8LE Information on slate and stone-slate roofing is available at www. stoneroof.org.uk/ historic/Historic_ Roofs Terry Hughes is chair of the Stone Roofing Association and a specialist consultant. He has been a member of the BSI slating and tiling committees since 1983, and was chair of the European slate committee from its inception in 1988 to 2004, and continues as a member. The many types of valley slating were usually developed in response to the properties of the local stones or slates. Clockwise from top left: single-cut, shale, Welsh open, and collar-and-tie valleys.
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