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Why Beauvais Cathedral collapsed

Excerpts from the Society's Transactions

The paper "Beauvais Cathedral" by Jacques Heyman MA, PhD, FSA, FICE, is published in the Transactions of the Newcomen Society, 1967-68 Vol 40.

In his paper, the author describes the collapse of Beauvais Cathedral, and analyses its structure, with reference to other Gothic cathedrals and suggests the possible causes of failure. In these passages he discusses the rules by which Gothic cathedrals were built and the deterioration in design towards the end of the Gothic period which contributed to the collapse of Beauvais.

It is fashionable to deny that Gothic became decadent in the second half of the thirteenth century, and to assert that the cathedrals of Amiens, of Beauvais, and, perhaps, of Cologne, were not the supreme achievements of the discipline. As a matter of aesthetic opinion, it is possible to argue endlessly about the relative merits of this or that structure, built in this or that century. As a matter of structural fact there is almost no argument possible. The decay sensed by the eye after about 1250 stems from a slow relaxation of the firm structural grasp that had been acquired during the preceding hundred years.

… On the basis of twentieth century engineering technique, it seems that numerical rules of proportion are precisely those required for masonry construction; the stress level in most of the fabric of a Gothic cathedral is so low that strength of the material is of only secondary importance. But such numerical rules could have been constructed in the twelfth and thirteenth centuries only empirically by trial and error, and by taking note of structural successes, and most importantly, of structural failures. Once this experience was no longer within living memory, there was no way of reconstructing the rules by any process of thought or intellectual argument. If the rules were followed, a safe structure probably resulted; if they were tampered with (say for "aesthetic" reasons) a safe structure probably still resulted. Any structural disaster after the middle of the thirteenth century, it is almost safe to say, can be attributed to ignorance of the rules, to gross tampering with the rules, to workmanship so poor as to be fraudulent, or to a simple Act of God.

Reconstruction of the original plan, by Viollet-le-Duc

Beauvais seems to have been particularly unfortunate. The apse and choir were started in 1247, and finished in 1272. On 29 November 1284 the vault fell... Whatever the actual reason, it was certainly believed at the time that the pier spacing was too large, and the repairs over the next 50 years included the intercalation of piers between these originally built for the choir, so that the bays were halved from about 9m to about 4.5m. The choir had been rebuilt by about 1337 but work was interrupted for the next 150 years by the Hundred Years War and by the English occupation. It was not until 1500 that a start was made on the transept...

The transept being well under way, the Bishop and Chapter called in expertise in 1544 on the subject of a tower over the crossing, at which masons and carpenters were to decide whether the tower should be of stone or timber. Models were examined in 1547, but it was not until 1558 that a decision was made in favour of a masonry tower, and it was 1564 before Jean Vast started the construction. This tower, completed in 1569, was immense, rising 153m from the ground, and alarmed the Chapter from the first. Several examinations were made, and the detailed report of two King's masons, Giles de Harlay and Nicolas Tiersault, about 2 years after completion of the tower, found that the four main crossing piers were beginning to lean…

…The masons proposed as a remedy the immediate erection of two nave bays, and the strengthening of the pier foundations. In the meantime, temporary walls were recommended between the crossing and the piers. The Chapter was pusillanimous, sought further advice, and only two years later finally decided on 17 April 1593, to put the work in hand. Thirteen days later, on Ascension Day, 30 April, the tower fell… The clergy and people had just left the cathedral in procession; only three people were left inside, and all three escaped. The Chapter decided to celebrate annually on 30 April the signal protection that the faithful of Beauvais had been afforded… There were sporadic attempts to complete the cathedral, but in 1605 the decision was taken to consolidate the existing work, and Beauvais became what it is today, a choir and transept without a nave.

There seems little doubt, however, that had the advice of the King's masons been taken in 1571, and the crossing piers braced, the tower might be standing today. It seems that the structure, from 1569 when the tower was completed, until 1573, when it fell, was never truly in equilibrium... The structural system of a massive tower supported by four unbraced piers would be liable to "drift", the movement restrained by tensile and shearing stresses developed in the mortar, and by possible interlocking of stones. Eventually, however, the columns would have been pushed so far out of true as to be useless. The Chapter was right to call a halt in 1605: "le temps n'était plus a bâtir des cathédrales".

The complete text of this paper can be purchased on line from our archive.

See also Cathedral Studies: Engineering or History? by N A F Smith, published in Transactions, Volume 73:1 (2001-2002). Copies of this prizewinning paper, can be purchasedfrom the Newcomen Society Office.

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