BCX)l(S MUD,MUD, GLORIOUSMUD Earth - The Conservation and Repair of Bow/Jill, Exeter: Working With Cob. English Heritage Research Transactions: Research and CaseStudies in Architectural Conservation Volume 3. Ray Harrison. James and James (Science Publishers) Ltd, 35 - 37 William Road, London, NWl 3ER, UK. 1999. 108pp. A4. 19 colour plates, 250 black and white plates and drawings. Softback. ISBN 1 873936 64 8 £30 This is one of a series of research transactions commissioned by English Heritage to help fulfil its role in securing the welfare of historic structures and advancing knowledge of their preservation. So far, six volumes have been published or are imminent, these covering metals, stone, wood, earth, and two on thatching in England. With the reawakening of interest in earth walled construction, both in terms of its historical significance and its benefit as a 'green' material, the publication of this case study covering earth walling and daub at Bowhill, Exeter, is most timely. The first part of the study places Bowhill and the works in a broad context and explains the role of the state in the direct conservation of historic buildings. Bowhill is grade 1 listed, being a small manor house or mansion of around 1500. The main surviving elements of this courtyard house are its open hall with screens passage and its two storey south range comprising first floor chambers over parlour and service rooms. The construction is of jointed crucks with the vertical elements set in largely cob walling. As the author, Ray Harrison, explains, 'Bowhill is important amongst houses of its type. . It is outstanding, even at the national level, because of the timber roof structures of the ball and great chamber'. Here, then, is a building of high status which includes cob as a major constructional element. This surely gives the lie to the common assumption that cob is an inferior material of low durability used only in humble vernacular buildings. Bowhill was taken into state guardianship as a threatened building in 1976. English Heritage took over responsibility in 1984 from the Directorate of Ancient Monuments and His48 toric Buildings at the Department of the Environment. This volume focuses primarily on repairs and re-instatement during the period 1990 to 1995. Considerable work had been undertaken during the earlier years, but a lack of records from that period has prevented detailed commentatywithin this volume of the initial repair work. As a prelude to his commentary on the repair and reinstatement works, the author has included a brief but very informative background on the place of earth walling and daub both within Devon and throughout the British Isles. This includes an assessment of the physical qualities of the materials, the common problems encountered, and the difficulties in implementing repairs. Commentary on the changing approaches to conservation exhibited at Bowhill is covered separately in an article by Ray Harrison in the ASCHB Transactions, 20 0996). The reason for omitting it from this volume is not given, but perhaps rests with a desire to focus on the practical aspects rather than the philosophical background. The main body of the work starts with a chapter covering the techniques of mixing cob and daub, and making cob blocks. This is followed by an account of the building of a new cob cross wall between the oriel and inner chambers. Further chapters cover cob repairs, daub repairs, plasters and renders. Collectively, these chapters deal with a wide range of situations, including the repair of some attendant structural elements such as beams and lintels. Until the mid 1990s, English Heritage had in place a direct labour system which enabled specialist staff to be brought in as and when required from some of their other sites. Whilst this differs from the usual contract procedures generally in place nowadays, it has facilitated controlled experiments in repair and reinstatement. The range of situations covered is probably wider than elsewhere in Devon, and perhaps beyond. Generally, materials closely matching the original have been used, and although little information on costs or time spent is included, the author has grasped the opportunity to record thoroughly these exempla1y repairs. The account of how the different methods have been considered, selected and implemented is clearly presented both in text and ample illustrations, and includes very useful commentary on how the problems of dealing with drying shrinkage have been addressed. This book is a worthy addition to the growing number of texts on earth building, usefully extending the volume of information about repair and reinstatement techniques. It deserves to take its place alongside the recently reissued ' 'Building in Cob, Pise and Stabilised Earth' by Clough Williams-Ellis, and undoubtedly will serve as a valuable aid in promoting practical and sympathetic care and repair of earth buildings. Bob Notber REDRESSINGTHE BALANCE SIru ctural Repair o/Traditional Buildings P Robson. Donhead Publishing Ltd, Lower Coombe, Don head St Ma1y, Shaftesbury, Dorset SP7 9LY 01747 828422. 312pp 148 b/w drawings/diagrams. Hardback. ISBN 1873394 40 3 £37.00. Training in the construction industry and professions continues to be focused on new build rather than refurbishment. This book aims to redress that balance in relation to structural matters by providing architects, surveyors, and structural engineers more used to new design, and students, with an appreciation of the technical principles governing structural repair. The difficulty the author faced, and acknowledges, is that his readers may have widely differing appreciation from one topic to another, yet each needs to be able to understand the basics. The resulting mixture of concentrated textbook and succinct coverage of a wide range of problems does not make for particularly easy reading. I found myself thinking of a highly-distilled version of Melville and Gordon's "The Repair and Maintenance of Houses", with much of that book's text boiled away, but going into greater depth in its narrower field. The four sections cover: Basics; Defects; Options; and Management. The first three chapters ( "Structural Beha viou r", "Soil Behaviour", and "Uncertainty and Performance") may seem like part of a structural engineers' textbook, but provide a useful summary for others. Most importantly, the third chapter makes the point that observation of an existing structure's performance can be more sophisticated than an engineer's model for a new building. The examples used include timber floors and stone cantilever stairs. These chapters are followed by just 3 pages on "Conservation": a chapter which refers to the new British Standard and provides a very basic summary of conservation concerns. Readers are advised that "There are many publications that describe how the protective system works (see Further reading). In addition, the local planning department or Conservation Officer will normally be able to give practical advice, if asked in good time". This treament is too cursory to give someone new to the field an adequate picture: while the extensive bibliography includes a very good selection of relevant material (from PPG 15and English Heritage's "Principles of Repair" to a wide range of more specialist publications, including the same author's Structural Appraisal of Traditional Buildings) there is no attempt to guide the reader to the key texts for further information (an opportunity missed). The "Basics" section concludes with chapters on "Health and Safety" and "Diagnosis". The second part "Defects" starts with an extremely useful summary of causes of structural damage, before considering "Below Ground Defects", "Ground Floor Defects", "Loss of Equilibrium" (in which it warns of the possible implications of, for example, notching for services in timber joists or masonry walls), "Movement" , "Fire", "Chemical Attack on Concrete" and "Deterioration". The third part "Options" contains the meat of material likely to be of particular interest to Context readers, with clear and succinct coverage of a wide range of issues and possible approaches. Starting with "Purposes of Repair", this section covers "Foundations", "Timber", "Masonry", "Weak Materials" (soft stone and unfired earth) and "Restraints". The final part "Management" covers "Preventive Maintenance", "Planning and Conducting Work", "Insured Perils" ,· "Law", and "Surprises". The "Law" chapter is largely devoted to the process of organising repair works -tort, Context65Morch 2000
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