Structure Review: St. Paul's Cathedral, London 🇬🇧

Structure Review

St Paul's, London by Mark Fosh

General Info 📚

• Location: London, EC4, UK

• Style: English Baroque

• Years of construction: 1256 and 1675

• Construction cost: cost covered by a special tax on coal

• Total height: 365FT (111 m)

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Design 🏗

Design of St Paul's was very challenging due to the relatively weak London's clay, meaning the heavy structure would sink through the years. St Paul's is unusual among cathedrals in that there is a crypt, the largest in Europe.

Half the space of the crypt is taken up by massive piers which spread the weight of the much slimmer piers of the church above.8 piers support the dome of the cathedral which is frankly unusual since only four pier foundations were used on most cathedrals at that time.

William Dickinson's plan for the floor paving (1709–1710)

Another challenge was the height of the dome. Christopher Wren was to create a landmark dome for the city of London. Wren planned a double-shelled dome, as at St Peter's Basilica.

His solution to the visual problem was to separate the heights of the inner and outer dome to a much greater extent than had been done by Michelangelo at St Peter's, drafting both as catenary curves, rather than as hemispheres.

Wren inserted a brick cone which supports both the timbers of the outer, lead-covered dome and the weight of the ornate stone lantern that rises above it. Both the cone and the inner dome are 18 inches (45 cm ) thick and are supported by wrought iron chains at intervals in the brick cone and around the cornice of the peristyle of the inner dome to prevent spreading and cracking.

Cross-section showing the brick cone of the dome

History 📑

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Old St Paul's 1087 - 1666

The Normans began building the ''old St Paul's". During the period of construction, the style of architecture had changed from Romanesque to Gothic and this was reflected in the pointed arches and larger windows of the upper parts and East End of the building.

Dimensions of the cathedral were, 585 feet (178 m) long and 100 feet (30 m) wide (290 feet or 87 m across the transepts and crossing. The spire was about 489 feet (149 m) in height.

Present St Paul's 1669-1708

In July 1668 Dean William Sancroft wrote to Wren that he was charged by the Archbishop of Canterbury, in agreement with the Bishops of London and Oxford, to design a new cathedral that was "handsome and noble to all the ends of it and to the reputation of the City and the nation".

Wren planned to replace the dilapidated tower with a dome, using the existing structure as a scaffold. The result was the present iconic St Paul's as it is known to everyone.

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Source: Wikipedia

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