What was Old London Bridge like, and why was it always being repaired?

Old London Bridge was a medieval stone bridge, completed in 1209, that carried a street of houses and was home to around 500 people. It needed constant repair mainly because its massive foundations narrowed the Thames and made the water rush through the arches, which kept scouring the supports. Sources also point to fire, ice and a drawbridge that had to be replaced more than once. [1] [2]

The bridge replaced an earlier wooden crossing and stood about 150 feet east of the present London Bridge. It was the only fixed crossing of the Thames downstream of Kingston-upon-Thames until Fulham Bridge was built in 1729. Its 19 piers were linked by arches averaging 24 feet wide, wide for the period, when the average bridge arch was under 18 feet. A drawbridge gap let masted boats pass. [1]

The bridge was not straight, with slight kinks between its three sections, and the piers were irregularly spaced and varied in width and angle. The middle pier, which held a chapel, was much larger than the others. Houses were built along it, and the roadway was narrow: in 1683 the surveyor William Leybourn recorded a width of 12 feet 5 inches beneath Nonsuch House and 18 feet 5 inches near the Southwark bank. [3] [1]

Houses were planned from the start, and inhabited bridges were common in Europe, with rents paying for maintenance. Guide London reports about 140 houses holding 800 people in the fourteenth century, with the population averaging 500. Rents were the main income of Bridge House, a body dependent on the City of London, which also took tolls from carts and boats. [1] [3]

The houses were far larger than on other European bridges. Dorian Gerhold notes that they had only a toe-hold of 2 to 5 feet on each side of the bridge itself and extended up to 34 feet out. Roughly every alternate house was part of a cross-building straddling the road, which created tunnel-like stretches. Struts lodged in the piers helped hold the overhanging parts up. [1] [3]

The protective starlings around the piers shrank the river to 508 feet at high tide and 237 feet at low tide, about a quarter of its full width. The bridge acted as a dam, with water levels differing by up to 5 feet from one side to the other. The accelerated flow made shooting the bridge dangerous and constantly scoured the foundations. Erosion contributed to collapses: five piers fell with their houses in 1281, and two arches in 1437. [1] [3]

Engineer Roger Hobbs of Imperial College London says bridge piers are liable to damage from shipping and the force of the river, and need maintenance before problems become dangerous. He says this finished the life of the medieval bridge and probably earlier ones. The bridge did not simply fall down, though; it survived two major fires and was removed by design. Narrow roadway problems led to the houses being cleared by 1761, and an Act of 1823 authorised a replacement, Rennie's bridge, which opened in 1831. [4] [1]