HC Deb 20 November 1957 vol 578 cc42-3W
78. Mr. de Freitas

asked the Secretary of State for Air whether he will make a statement on the effects of sonic booms on buildings, especially on glasshouses, windows and plaster ceilings; and how many claims for damage by the public his Department has investigated in the last three years.

Mr. Ward

Fourteen hundred and thirty-nine claims have been investigated in the last three years. The effect of sonic booms on buildings is at present being investigated by the Building Research Station of the Department of Scientific and Industrial Research. The investigation includes the measurement of the pressures set up by a sonic boom and of the vibrations induced by it; and also the examination of buildings which are reported by the owners or tenants as having been damaged. I understand that information from the direct measurement of pressures is as yet incomplete. The following are the general conclusions so far reached from the survey of buildings.

No damage to the main structure of buildings has been as yet observed. On the whole, such damage as can properly be ascribed to sonic booms has been limited almost entirely to some breakage of glass in greenhouses and windows, a few falls of small areas of old plaster-work, and, in some instances, dislodging of the plaster which has been used to repair cracks in old plasterwork.

There is no reason to doubt that complaints of damage to property are made in good faith. But the actual amount of damage which on investigation can be ascribed only to a sonic boom is much less than has been claimed.

Ceilings in most houses have cracked at some time. Cracks are filled and concealed on re-decorating but they generally reappear very soon after the work has been completed. The filling and the overlying distemper are loosened and are ready to fall with the slightest disturbance of the building, e.g. by slamming a door. Some booms may set up sufficient vibration to cause this material, as well as already loose patches of old ceiling to fall. But no example has yet been seen of new cracks having been caused by a sonic boom.

Glass in windows and greenhouses may crack, or be in a condition to crack with little additional pressure, because of factors other than the sonic boom. Often the condition of the crack shows it to be an old one not noticed by the owner until attention is drawn to it by the fear of possible damage associated with the boom.

The investigation is continuing.