28 Andrew Vines is the latest Conservation Officer to benefit from the SPAB course and report back THE SPABAUTUMN REPAIRCOURSE We took the cement off and rendered the front of the house with lime, just as we were advised, and now all my wallpaper's falling off It's the sort of telephone call you would rather not receive at the end of the week. A few days later, and not having had time to resolve the problem, I set off for the SPAB repair course in London, with this agitated caller's voice ringing in my ears. The use of lime, its rediscovery, versatility and beneficial properties for historic buildings was a recurring theme of the week, although the course subjects were many and varied,. Several speakers' enthusiasm for the material was tempered by the message that success only comes with experience of how to work traditional mortars, plasters and renders and an understanding of how they perform in practice. For example, knowing how long to work lime plaster when applying it to an interior may vary from one mix to another and can only really be gained by experience. Our knowledge of the effectiveness of different pozzolanic additives may still only be partially complete, whilst research on the addition of cement shows that it may inhibit the carbonation of lime. Conventional wisdom that lime renders cannot be used on sandstones may not be entirely true. It appears that sandstone was often limewashed pre1850 and current research centres around the reaction of the lime with the binding agents in certain sandstones; other types may be entirely suitable to receive lime treatments. Clearly it is only when our knowledge in these areas is more complete that the Conservation Officer can promote such traditional techniques with total confidence. Previous generations would no doubt have built up their knowledge of lime over many years of trial and error whereas today we may try to rediscover the material from a more scientific standpoint. One speaker on the SPAB course stressed that we sometimes try to be cleverer than we need to be when adopting the best practice. Some contractors have realised that the best results are only achieved by adhering to traditional ways of preparing and applying lime-based materials. 'Convincing many builders and contractors who are new to such materials, with time and costs against them, may be an uphill struggle. ' ' "I couldn't do this every day or I would go bust" was the rather disappointing comment of the builder. ' Some of these issues became apparent during the SPABstudy tours. A renovation project on a modest 18th century house in Spitalfields, East London, made widespread use of traditional materials both inside and out, including rivened oak lath ceilings, lime plasters, and limewashed internal surfaces using traditional pigments. The contractors had learnt to handle these during the course of the work, but the process had not been without frustration. A lime plaster ceiling had refused to adhere even after the third attempt, but once the material had been mastered it was claimed to be as easy to handle in its own way as modern plaster. The builder's enthusiasm for these new-found techniques was real and not merely laid on for the visit - although someone did claim they had spotted a bag of cement in the cellar! Contractors elsewhere commented that mixing lime putty and sand takes a certain amount of conviction as it remains 'dry' for a long time before suddenly becoming 'wet' and thereby useable. Convincing many builders and contractors who are new to such materials, with time and costs against them, may be an uphill struggle. The cost of the work at Spitalfields, when compared with a 'rip-out and start again' specification had increased by some 25%. "I couldn't do this every day or I would go bust" was the rather disappointing comment of the builder, who reckoned he had not made anything on the job, but it had nevertheless been good for business. No doubt more widespread use of such materials will bring costs down in time. At present lime putty is fairly expensive as demand remains relatively small. Greater experience should also allow builders to price such jobs more accurately. During another part of the course, Ian Constantinides of St Blaise noted that his firm is developing a fairly sophisticated book of rates based on time and motion studies for handling different types of plasters and renders. A visit to St Margaret's Church, Blackheath, showed the effects of limewash applied to the exterior of an imposing Victorian Gothic church, clad largely in Roman cement with freestone dressings and spire. Much of the work concerned its fine interior including the restoration of wall paintings, CONTEXT 50
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