Are stone bridges really old-fashioned? Are ‘modern’ bridges so much more advanced? About 40% of bridges in the UK are masonry (stone or brick) and most of them were built 100-200 years ago. There are several examples of masonry bridges that were built by the Romans and are around 2000 years old. Are our new concrete are steel bridges likely to last 100, 200 or 2000 years? Probably not. The builders at the time knew something that we may have forgotten since.
What about sustainability? Are bridges that are likely to be often replaced within 50-100 years (1-2 generations) really sustainable? Longer lasting bridges are likely to be more sustainable on the long-term and have significantly lower impact on the environment. We need to think about how we think…
Would a classical stone bridge be suitable for the location?
A stone arch bridge is proposed to be appropriate for the area and respect the classical architecture in Clifton. Limestone of similar characteristics is intended to be used.
These bridges were designed to carry horse and carts or the occasional steam trains. Yet today they carry lorries, cars and heavy goods trains. This traffic which is many times heavier, faster and denser than the old engineers would have ever imagined. At the time the bridges were built to last. They were overdesigned, which is why we are lucky enough to have the current road and rail network. About 40% of all bridges in Britain and in Europe are were built out of masonry (stone or brick). Six out of ten of these masonry arch bridges are over 100 years old, but many examples are as old as 2000 years and were built by the Romans (think about the magnificent Pont du Guard). Clearly, the old masters have got something right.
No stone bridges have been built in Britain or Europe for around 100 years. Skills and experience in building stone bridge have been lost. Perhaps we have the opportunity to review lost skills and pass them onto future generations.
How long will this stone bridge last?
The primary aim of the project is to provide a safe crossing for pedestrians and cyclists enjoying the Downs. However, we want to build a bridge that will far exceed the current design life for new bridges (120 years!) and will last for a minimum of 300 years. The project would also re-generate traditional stonemasonry skills and offer a whole range of other benefits (e.g. educational, community, job creation, local employment) for Bristol and the surrounding area.
Isn’t building a stone bridge going to be too expensive?
Most engineers would expect masonry bridges to be much more expensive than concrete or steel bridges. However, using traditional building processes together with current technology (e.g. stone cutting or lifting equipment) is expected to make the costs competitive and a stone bridge a feasible option. Over the long term (300+ years), stone bridges need very little maintenance (compared to painting steel bridges at regular intervals for example) and would therefore be far cheaper to maintain than any other bridge type.
Take a walk around Britain’s magnificent medieval cathedrals. What you will see is the result of centuries of experience passed on to generation after generation of stonemason. Every moulding cut by hand, every tool mark made by a mallet and chisel of a master craftsman from a bygone era.
The same may be said of our heritage of stone bridges, an ultimate architectural solution that we simply take for granted. How often, whilst passing under, or crossing over a stone bridge have you stopped to appreciate the work that went into this, the most humble of constructions? No one comes to worship at a bridge as they do at a cathedral, yet the skills and talent that went into building both come from the same inspiration: man’s ability to transform stone from the ground into beautiful, elegant, timeless structures.
How did they lift those huge stones up to construct the arches? How is something so seemingly delicate able to stand on its own, let alone carry load above? It is by asking such questions that the true majesty of stone bridges starts to emerge. One thing can be said for certain. If these skills and knowledge are not nurtured and passed on to the next generation, we are doing a huge injustice to our forebears and will lose a unique aspect of Britain’s heritage.