Bald arch

Bald arch is a technical term used by engineers to describe the decay of the crucial keystones in medieval buildings, particularly churches and cathedrals.

Causes and symptoms

Many attribute the decay to low pitch vibrations produced by late 19th Century pipe organs, the proliferation of the 32 feet pipe particularly responsible, although some blame the vibrations from inner city traffic. The stone becomes crumbly, producing a fine powdered stone. Also, large sections loosen and often fall off, creating another hazard.

Remedies

The arches can be reinforced using steel trusses. Some opponents believe that this degrades the appearance of the arches, that it makes them look like dental braces. Without this support, the building would be structurally unsound.

Examples

On Wednesday, 14 March 2003, the church of St Alfwold in the village of Ramsbury in England was closed temporarily while the masonry was reinforced with steel braces. An example of the damaged stonework is on display in the shop and has been made into a box for donations.

Further reading

• The Observer’s Book of Architecture – John Penoyre and Michael Ryan
• The Churchwarden’s Guide to Church Maintenance – James Redcock