C O N T E X T 1 3 3 : M A R C H 2 0 1 4 9 A church at Llanfair Gilgeddin inWales with a distorted gable wall that was about to be pulled down is now in the care of Friends of the Friendless Churches. SUPPORTING COLUMNS Structural cracking to historic structures Structural engineer Brian Morton encourages professional advisers to think twice about major rebuilding or underpinning when simply making good may be enough. I have recently been reminded how little newly qualified engineers understand about the structure of historic buildings. If the codes of practice and buildings regulations are not complied with, ‘the building will fall down’, we are told, regardless of its existence for hundreds of years. But practical experience and understanding of how structures work is vital before drawing any conclusions as to necessary work to stabilise a cracked structure. A significant amount of my involvement is in inspecting churches as honorary engineer to four diocesan advisory committees (DACs).This involves looking at proposals put forward by other engineers or architects to remedy and stabilise structures that are causing some concern to the church and parochial church council. These structures are mostly constructed of stone or brickwork, but there are sometimes elements constructed of timber. In order for this article to be balanced, I have also considered non-secular buildings, where generally I have been asked to give an opinion with regard to the stability of solid walls constructed of brickwork, thin stone or flint. To simplify this article, I have first assumed that brick and stone structures of historic buildings have similar crude foundations from earlier time, which gradually become more sophisticated.This is particularly so with brick structures which, because of their comparative thinness compared with stone walls, tend to have stepped-out spread bases. However, earlier walls of brickwork are generally found to be set onto flint or rubble stone, simply dropped into trenches of shallow depth. Stone buildings generally of comparatively massive construction were also built on rubble or flint, generally loosely dropped into trenches and usually mixed with lime to hold this fill material together. Stone columns or brick piers, on the other hand, would have spread foundations to carry the high concentrated load. Walls very rarely fail in direct compression because, historically, the builders made walls thick enough at their base to support the loading from the particular height of the structure.Walls were generally restrained horizontally by floors and roofs, and thus a wall built vertically adequately restrainedwill have a good chance of AVictorian tower to a church in Lincolnshire, built over graves, was about to be demolished, but was saved.
RkJQdWJsaXNoZXIy MjgyMjA=