8 C O N T E X T 1 2 4 : M A Y 2 0 1 2 Supporting Columns My years in conservation Ian Hume, who confesses to being a ‘fairly ancient’ conservation structural engineer, reflects on a long career, and regrets that common sense is no longer all that common. This the story of how failing the 11+ entrance examination to the local grammar school led to some 8th century Hindu temples in Cambodia and toWestminster Abbey, by way of a multitude of fascinating buildings and structures. My family tree has a fair sprinkling of carpenters, masons and builders (plus the occasional publican and draper), so perhaps the building trade is in the genes. Going to a secondary modern school rather than a grammar school led to learning technical drawing, and gaining a strong urge to become a draughtsman. Nobody from my school went to university, so on leaving school I went into employment with the Ministry ofWorks as a student draughtsman. I did a day release course at what was then the Brixton School of Building. The first tasks of a student draughtsman were learning how to print neatly (I never really mastered that), and how to draw in pencil on tracing paper and on tracing linen in ink, all for £2 13s 4d (£2.67) per week. Dad thought I was overpaid. College studies included the design of reinforced concrete and structural steelwork buildings, using the relatively simple analytical methods that existed in those days. Slide rules were used, calculators unheard of and computers decades away.Those simple thought processes of how structures work and the straightforward analytical techniques have stood me in good stead over the years. Getting complicated in thinking about structural analysis of buildings has never seemed to me like a good thing or indeed, except rarely, necessary. Nothing built before about 1860 was designed in the modern structural sense. Even after that, analytical methods were straightforward. Structures were built by people who understood by experience, and by quite simple thought processes, how they worked and how far they could push the limits.That is not to say they were simple people. Far from it. Clearly the people who developed the great gothic cathedrals,whenmost folkwere living in very rudimentary homes, were far sighted and clear thinking.Their designs were based on a clear understanding of the strength of materials and of how forces flowed around walls, vaults and buttresses, and on into the ground. A computer can not do much better when one bears in mind that a small parish church, let alone a great cathedral, is composed of countless small elements of stone of a multiplicity of shapes bedded on mortar of various qualities and thicknesses. It is impossible to model all this in a computer. Any results emanating from computers can be no more than a guide to the stresses that arise. We can now analyse the stresses in timber beams to umpteen places of decimals. But we come to more or less the same conclusions on the size of joists in domestic buildings as we did when all we had to do was measure the span in feet, call it inches, divide by two and add one inch.Thus a 12-foot span joist was seven inches deep (12 divided by 2 = 6 plus 1 = 7"). Sorry to all you metricated people, but it only works in feet and inches. (See ‘Floor loadings in historic buildings’, Context 70, June 2001). Not long ago I was asked to look at proposals for repairs to a major monument in south east Asia. A great deal of computer analysis (many tens of thousands of dollars’ worth) had been done on a structure which had stood the test of time and the elements for about 800 years.The results were seriously impressive visually but made very little impact on decisions for its future repair. The best way to repair the monument was to ensure that its original and successful construction details were maintained. I also studied traditional building construction. That no doubt proved to be almost totally useless for those in the class who spent all their lives dealing with modern structures, but it was invaluable to those of us who went on to deal with old ones. If we understand how a building or structure was put together, we can understand how it stands up, what might be wrong with it, where to look for possible problems, and what the best solutions to those problems might be. Learning about traditional building construction has helped me sound as though I knew what I was talking about when on site. I understood that kneelers are to be found in gable walls of a church as well as in the pews, No 2 Carlton Gardens, London.The decaying building had stood completely open to the elements for some 17 years.
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