MODERN FIREPROOFING METHODS.
As Adopted in Large Cities.
William Copeland Furber read a paper on “Some features of the design and construction of high buildings” before the Engineers’ Club of Philadelphia, extracts from which referring to fireproofing are given here in a condensed form.
Most of the high office buildings of the day are built according to the prevailing method of fireproofing, although in Philadelphia several apartment houses of considerable height have been built with wooden internal construction. Legislation on fireproofing certain classes of buildings has already been enacted. In New York hotels, lodging houses, schools, theatres, jails, police stations, charitable institutions, hospitals, and asylums, which exceed thirty-five feet in height shall be of fireproof construe tion. as well as any other building exceeding seventyfive feet in height. St. Louis has a somewhat similar construction; and the great loss of life in the Windsor hotel. New York, and the Hotel Jefferson. Richmond, Va., should insure fireproof construction for all hotels and combustible buildings everywhere. To preserve the integrity of the structure the tempera ture of the steel framework should never greatly exceed 400° Fahr.: to guard against the accidental ap plication of great heat, the steel must be covered with a non-conducting covering capable of resisting disintegration on a rapid change of temperature, as from a red beat to a temperature of a stream of water. Such a material is fire-clay seiniporous terra cotta, which can be heated red hot and then plunged into water without any apparent disintegration. The fireclay is a native combination of the hydrated silicates of alumina, mechanically mixed with silica and alumina in various subdivisions, and sufficiently free from the silicates of the alkalies and from iron and lime to resist vitrification at high temperatures. Fireclay contains from forty-seven to eighty per cent, silica and from seventeen to forty-eight per cent, alumina, and is probably the most durable substance that can be applied to protect iron from beat, provided, of course, it is applied with sufficient thickness. Too many architects are stingy in this respect in their endeavor to gain all the space possible. Hence the destruction of several fireproof steel buildings has resulted not from the system, but the method adopted. The necessity for dead air-space cells, also, makes it more difficult to insulate the structural work bv preventing any considerable reduction of heat from the point of application. A column and beam, not being able to give up their heat by conduction and radiation, store it up. and are, therefore, placed in an unfavorable position compared with a lamp chimney, which is kept below the melting point of glass, because the heat of the flame is rapidly carried away by radiation and the upward current of air, and is not stored up. The dead air-space cells, however. play a very important part in fireproofing and are highly effective in the non-conduction of heat. Some authorities give the thermal conductivity of air as one thirty-five hundredth part of that of iron, but the data relating to these matters are not complete nor in very satisfactory shape. The value of dead-air spaces, however, is very great, and the use of aircells in terra-cotta fireproofing is essential. Fire-clay with air-cells has may times the efficiency of the solid material, and they should be employed in making fireproof coverings. The protection the beam should have is determined by the maximum temperature to which it is likely to be exposed; in conflagrations temperatures of 2,500° Fahr. are easily obtained at a lard refinery fire at Fifty-ninth street and Eleventh avenue, New York, some years ago the temperature was 5,000°. In most buildings a one-inch covering of porous terra-cotta alone protects the lower flanges of the I-beam; the girders usually have a trifle more —one inch and one-half or two inches. No system of fireproofing, however, can be considered complete unless the exterior as well as the interior is protected by an automatic steam underwriters’ fire pump. The exterior should have distributing pipes pierced with holes, running horizontally round the building at intervals of several stories, connected with the main supply pipes to permit a sheet or curtain of water to be distributed over the face of any exposed side, to protect it from any adjacent fire. The interior should be protected by the usual inside standpipes, with hose and reel on every floor. The source of water from which the fire pumps derive their supply should be separate, if possible, from the source which supplies the engines of the fire department.
It may be added that the height of a building need be no obstacle to the fire department in the event of a fire breaking out even on the topmost floor. Given standpipes, with hose at every landing, and elevators in working order, and Chief Musham, in Chicago (where the limit as to the height of such buildings has just been removed), or Chief Croker, in New York, will be able to fight any fire that breaks out in them.
The illustrations accompanying this article show a design for a fireproof office building completed and a fireproof store building and warehouse in course of erection at Philadelphia.