How Can We Measure The Lifespan of A Building?

Lewes Castle in East Sussex was in the news last week when a wall collapsed. Luckily no one was hurt and structural engineers have been called in to investigate why the wall fell down. The castle is one of the oldest in the country, built just after the Norman Conquest in the late 11^th Century. This being the case, I wondered just how long can a building be expected to last?

Reading around this subject I found a range of opinion on the average lifespan of a building. Brick buildings are apparently most reliable, lasting for 100 years or more as, perhaps surprisingly, are wooden structures – although think ancient cathedrals with their hefty wooden frames. Between 50-100 years seemed to be most common for those made of concrete, some commenting that a building may last up to 150 years whereas others may be falling down after just 20! Here, perhaps, lies the point, that there are many variables involved. Quality of the materials used is a key issue, along with how much attention is given to regular maintenance and checks for leaks, damaged mortar and cracks. The structural design of a building also plays its part. If areas are not strong enough or carry too great a load this will lead to problems, as will inadequate foundations.

Today’s precision engineered construction materials allow for beautiful, sleek modern design which many believe has great positive impact on our built environment. The flip side of this can be seen in the thick columns, beams and slabs of older buildings, many of which are however still pleasing to the eye. Concerns about cost and the environment may rightly encourage the use of less raw material, but will these buildings still be standing in hundreds of years?

Lewes Castle was built out of raw stone to withstand attack from medieval adversaries. At getting on for 1000 years old it has outlived almost every other building built at that time but, despite being inspected regularly by experts, has perhaps simply reached the end of its natural life. Whatever the verdict, it remains a fine example of the skills of our engineering ancestors.