Soaring Monuments
Heavy stones were brought to the site by water or cart. The masons of Laon Cathedral in France, grateful to the oxen that pulled their carts, carved oxen peeking out of the top of the towers. Scaffolding was used to reach higher parts of the building, and ‘put-log’ holes for this are still visible on many cathedrals and castles. Cranes and pulleys also helped lift materials. Arches were supported using wooden frames called ‘centring’ which held the stones steady before the keystone at the top locked the whole thing into place.
Gothic cathedrals were usually supported on deep foundations and had thick walls to make them strong. Sometimes structural problems did appear, especially in the area of the crossing where the tall central tower was supported on relatively small piers, or pillars. At Salisbury Cathedral the 13th century tower was made too large, forcing its hasty reinforcement, whilst at Wells Cathedral, owl-eyed strainer arches had to be inserted to strengthen the crossing. Reinforcement did not always work, however, and at Ely the Norman crossing tower collapsed in 1322 and destroyed part of the choir. When the tower was rebuilt, light timber was used instead of heavy stone to create the large octagonal lantern we see today. Amazingly, such extreme measures were rarely needed.
Many of the apparently frivolous details on a Gothic cathedral have a structural purpose. Decorative details actually helped to strengthen weak points. The ornate pointed pinnacles at the corners of the building, for instance, add weight which helps to keep the corner strong, in the same way that pressing down on a pile of books will prevent them from toppling over. Arched flying buttresses make the cathedral look like a wedding cake but also keep the walls from falling outwards.
Source: BBC By: Carol Davidson Cragoe