Sometimes, we can’t see the evidence of thought in designing the building unless we attempt to trace it through careful measurement of the structure and spaces. Measuring is a great tool in getting to grips with the methods of the builders who once arrived at a site with pegs and rope to set out their resolved plan. If we’re lucky we might identify a system of repeated units or perhaps an overall dimension in a round number. In the middle ages, people tended to use the pole, a unit that varied between 16 and 18 feet in length, but occasionally, 20 feet, or maybe 24 feet might be chosen if it suited the site. In any case, Britain retained the use of the Roman foot, all of which makes imperial measurements helpful in identifying whatever system was used. Subsequent rebuildings might each incorporate existing structures, or perhaps demolish old walls, creating a mosaic of parts with no obvious system. But as a general rule, the grander the building, and the fewer periods of change, the likelier you’ll find clear measurements.

Proportion is another excellent method for the buildings archaeologist. Let’s say you have a medieval great hall which is 100 ft long by 40ft wide. You already have a measurement system involving 20 foot units. But those units are set proportionally as a 5 x 2 grid. Is this typical? Studies of medieval halls have in fact shown that fifteenth- and early sixteenth- century halls tend to have a larger area and are proportionally longer than thirteenth-century examples. The natural question is: why? Well, the broad proportions of the earlier examples might be due to their structure: by the twelfth century it was usual to have two parallel arcades within a hall, dividing the room into three long aisles, the arcades either supporting the roof in two places or dividing it into three (a high, pitched roof flanked by two low, sloping roofs). Later halls have no aisles, but a single roof over the whole width. So it makes sense that with extra supports, or three roofs side-by-side, a typical early hall would have the capacity to be wider than an unaisled later hall with its onerous single span. Later builders could make up for the resulting relative narrowness by extending the length of the hall, making its stretched proportions even more obvious.

When printed books offered interpretations of the principles of Classical architecture (strictly after 1486; more so after c. 1540), favourite proportions were promoted. Authors either advocated the instruction given in the only surviving treatise by an ancient Roman writer - Vitruvius (c.30 B.C.) - or they studied ancient monuments for themselves. Some created their own refinements of proportion. The square is one of the most basic of the classical proportions; permutations of squares and double-squares (and cubes and double-cubes for the volumes of halls and formal rooms) echo through the seventeenth-and eighteenth centuries. But there are many more latent ratios and geometries that manifest ideals of beauty.

Another means of diagnosing the changing eras of historic buildings is to observe advances in technology which can be subtle and far-reaching. Knowing that cast-iron framing was first used in a factory in the 1790s can give us a starting-date for any such building we come across. Soon, the early Victorians pioneered methods of glass manufacture that increased the possible size of window panes. In thousands of surviving houses across Britain glaziers installed one pane for the top sash, one for the bottom sash, rendering obsolete the century-old Georgian pattern of 3 x 4 panes. By 1851, Crystal Palace presented a world famous monument to the techniques and opportunities of mass-produced frameworks in iron and glass. Today, Manhattan, Shanghai and Canary Wharf continue the legacy. Even the most modern buildings are archaeology of a sort. 

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Content last updated: 29/11/2005

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