10 C O N T E X T 1 2 5 : J U LY 2 0 1 2 replaced, howwalls can be taken down prior to rebuilding and, a particular interest and recurring problem of mine, how delaminating faces on tall towers can be taken down and rebuilt.With any of these problems it is often best to consult a structural engineer who is experienced in such matters. Do old buildings and structures collapse without warning?Yes, but in my experience, apart from a couple of very badly decayed structures, collapses usually occur during repair works.There has not been sufficient attention paid to the detail of the temporary works, they have been put in the wrong place, they are too small or they have not been put in at all. It has long been my practice to ask to see details of the temporary works that the contractor proposes to use two weeks before they are installed. Although this muddies the waters of responsibility, I believe it to be vital. I may have been involved with the building for months, if not years, visited many times, and have a good understanding of how it works.The contractor, on the other hand, has probably not been involved for long at all. I can think of several cases where the contractor’s proposals might well have caused serious problems if not amended before installation, usually through a lack of understanding of how the building worked. This applies to anything from the use of a couple of telescopic props as to major temporary works schemes. Early reinforced concrete is worth a brief mention. There were some weird and wonderful methods of reinforcing concrete structures in the late 19th century and early 20th centuries. Some of the methods resemble the system of top and bottom bars with links with which we are all familiar, but many methods consisted of bottom reinforcing bars only,with no top reinforcement and little if anything by way of shear reinforcement.This may well influence the way in which the structure can be safely altered or how temporary works can be installed. Probably one of the most difficult things to do is to ‘uncondemn’ a building that someone else has condemned as incapable of conservation or repair. I have been asked to do this on a few occasions. It all boils down to understanding the structure, to inspection and to experience. I have one particularWestminster building in mind, which now stands happily albeit after some major intervention. I recall a great deal of rot and significant settlement, due to the almost total lack of foundations. Structural monitoring is a useful tool in the armoury of conservation structural engineers. Is it moving, how much is it moving and which way is it moving? My experience suggests that the longer one looks at cracking and deformation, the worse it seems to get. Cracks often get grubbier and settlement often looks worse than it did whenwe looked last time.Answering these questions often involves structural monitoring: the careful measurement of cracks, leans and settlements. Such measuring can be very expensive, but there are a number of modest ways of tackling the problem if the job you are dealing with can not support great expenditure. A series of articles in Context in March, June and September 1996 dealt with simple monitoring in some depth.We can be quite convinced that a structure is stable while others are convinced it is moving. All of this leads me on to a committee with which I have had a long involvement.The ConservationAccreditation Register for Engineers (CARE) lists structural and civil engineers who have proved to their peers that they have a good track record of dealing with historic fabric in a sensitive way. Find the list by going to the website of the Institution of Structural Engineers and typing CARE into the search box. Having encouraged you to ask the contractor what is proposed by way of temporary works, it is often a good idea to ask contractors and craftspeople how they would go about the repairs.They often have long experience and great skills, and professionals can often learn a great deal from them. Rather than concluding that I did not have a clue as to how to tackle a particular problem, craftspeople were always pleased to be asked for their views, happy to share experiences and ideas, and pleased that a professional thought their views and ideas important. Health and safety are clearly important but there is often a fine balancing act. I recall a debate about the relaying of the Donkey Road atWhitby.The road is paved with stone blocks and has distinct raised courses every 200mm or so to allow donkeys to grip the otherwise smooth surface of the steep pathway. Having been dug up in sections and relaid in a piecemeal fashion over the years for laying cables and so on, the road needed proper relaying.There was discussion about these raised courses causing a tripping hazard to people, there not being many working donkeys left in Whitby, as against the need to retain them as part of the character of the surface. In the end, the raised courses were preserved, their existence being considered to be clearly visible and regular in pattern. Inspections are very important. Do not ever jump to conclusions about what is wrong with a structure; check everything as best as you can. I recall visiting a country Some elaborate temporary works at Castle Howard Mausoleum Would you walk on this floor if you knew about the joist?
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