RIDDLE OF THE TILES

Press, Volume LXXXVIII, Issue 26869, 23 October 1952, Page 8

RIDDLE OF THE TILES

Cathedral Floor Disturbed

SPECIAL INVESTIGATION STARTED

For more than 50 years the mystery of the floor tiles in the Christchurcn Cathedral has remained unsolved. Periodically sections oi the tile nooning have lifted up like blisters—in some cases as much as four inches from the concrete floor beneath. -So lar the lifting of the tiles has not been explained saiislactorily, although many theories have been advanced. Now a detailed investigation is being made to establish, if possible, the reason or reasons for the disturbances which have been occurring since 1894, according to the minutes of the Cathedral Chapter. The investigator is a Christchurch layman associated with the Cathedral. He started his investigation about three weeks ago, and has discussed the lifting of the tiles with master builders, stone-masons, architects, people whose knowledge of the Cathedral goes back many years, and a physicist, a potter, and an industrial chemist.

One of the many theories advanced was tested in the Cathedral yesterday morning. It has been suggested in the gast that the movement of the tiles has een caused by extremes of temperature. A potter has stated that nonvitreous tiles like those laid in the Cathedral would expand .1 per cent, with a rise in temperature of 100 degrees Fahrenheit. To find how much movement could be caused by extreme temperature a quantity of dry ice was placed on a tile blister just inside the west door of the Cathedral. Four minutes after freezing the blister subsided 3-Bin, but two hours later it was back to normal, indicating that there is a great deal more movement of the tiles than could be caused by extremes of temperature. Among those present at the experiment were the Dean (the Very Rev. Martin Sullivan), the precentor of the Cathedral (Canon W. A. Orange). Mr R. S. D. Harman, architect to the Cathedral Chapter, the diocesan registrar (Mr L. H. Wilson) and Mr J. W. Graham, contractor for the Cathedral fabric.

All the theories that have been advanced about the movement of the tiles are being carefully investigated. The most ingenious theory so far is that the disturbances are related to the rise and fall of the tides. The lifting of the tiles has also been attributed frequently to the Cathedral being built on a swampy riverbed. Another suggestion, made in 1948, when many tiles in the main aisle were lifted and badly cracked, was that a slight settling of the foundations of the outer walls was responsible. This, however, is not accepted by ecclesiastical architects who know the history of ancient churches where foundations have settled. In such cases the tendency is for the flooring to be pulled ‘apart and not pushed together in such a way as to cause lifting.

Vibrations Set up by Organ A foreman mason who did much work on the floor in the Cathedral believes that vibrations set up by the organ have disturbed the tiles. In 1926 the organ was rebuilt and two new sets of pipes were added. The lowest pipe sounds a note of 16 vibrations a second, which is almost beyond the aural range. When sounded with other notes up the scale the resultant under tone is believed to cause sufficiently low vibration to disturb the tiles. The possibility that trams passing through Cathedral square may set up sympathetic vibrations in the Cathedral has not been disregarded in the present investigation. Chemical action between the limestone base and the hard cement crust setting the tiles which might generate gas has also been suggested as the reason for the lifting. Moisture from the foundations might be seeping up and aggravating the chemical action. Cleaning of the tiles also may have something to do with the disturbances. Two theories are that warm or hot water used for cleaning could cause saturation or that a detergent also used for cleaning might react with the cement.

Some people consider that the main floor of the Cathedral is on the move and the tiles are stable, hence the buckling up. There is also the suggestion that the Portland cement used nowadays does not allow the tiles to unite with the concrete containing lime that was probably used for laying the original floor. Trouble in 1894 In the minutes of the Cathedral Chapter the first reference to movement of the tiles is in 1894. There is a report by the architect, Mr C. W, A. Mountfort, that gaps cut in the tiles were already closing up, indicating expansion of the tiles. In 1905 Bishop Julius wrote to England seeking information about the occurrence, but the- minutes do not disclose if he obtained it.

TiFes in the north and south transept started lifting in 1907 and the Chapter consulted its architect. Damage was reported again next year because of rising of the tiles, and in 1916 Bishop Julius referred to the disturbance of the flooring. There was an eruption near the chancel steps in 1924 and some of the tiles were partly relaid in slate. In 1928 there was still trouble with tiles lifting. The representative of an English tile and pottery firm was consulted but could give no indication of the cause of the trouble.

In 1932 tiles were loosened and had to be replaced. Then in September of 1939 the chapel floor was forced up and broken, the tiles being shattered. More damage was done in January, 1948, and then in February, 1949, it was reported that nine square yards of tiles near the pulpit, and a further area of 20 square yards near the north transept had risen during the Christmas holidays. Since then there have been other eruptions, the latest being in January last year when tiles inside the north

porch door and just inside the west door came up in the familiar blisters. Some of these blisters were quite large. One measured during the investigation was Bft in diameter and the tiles had come away cleanly four inches clear of the floor. Tiles lifted last year are now being relaid. Work inside the north porch door has been almost completed, but another blister has risen right beside the slab of floor that has just been relaid. Inside the west door it is proposed to lay a trial set of tiles m a bituminous compound. This is expected to allow the tiles more give and /prevent the disturbance that has lasted so long. Some of the theories advanced have been eliminated in the investigation, but exactly why the tiles keep rising is not yet known. The riddle of the tiles may be difficult to solve.