MODERN BUILDINGS LACK FIREPROOF QUALITIES
Reports of Engineers to the United States Geological Survey.
Severe criticism of the lack of fireproof qualities in modern buildings is contained in the combined reports just submitted to the United States Geological Survey by Professor Frank Soule, dean of the College of Civil Engineering in the University of California, Captain John Stephen Sewell, Engineer Corps, U. S. A., and Richard L. Humphrey, expert in charge of the Structural Materials Division of the Technologic Branch of the Geological Survey and secretary of the National Advisory Board on Fuels and Structural Materials. These experts a short time ago completed a study of the condition of the buildings of San Francisco following the earthquake of April 18, 1906, and the fire which followed. They reach the conclusions that the lessons from the Chicago and Baltimore fires have not yet been learned and that a great conflagration, with its attendant loss of life and millions of dollars in property, is possible in every big city of the country. Professor Frank Soule, after giving the details of his investigation, sums up the situation in the following language: “The failure of
THE SAN FRANCISCO CASE.
fireproofing methods in San Francisco is directly traceable to the commands of the owners to their architects to cheapen, as far as practicable, the fireproofing and the construction generally, in order to secure greater interest on their investments. This cheapening has often occurred, in spite of the protests of the designer, and it is in an entirely wrong direction; for rates of insurance are largely reduced with improvements in fireproofing; and, as the cost of the steel frame and its proper fireproofing seldom exceeds twenty-seven per cent, of the cost of the building, it seems wise to protect the other seventy-three per cent, with adequate materials. In some instances in San Francisco, brick laid in rich Portland cement mortar has been found to be excellent fireproof covering. Good brick has withstood well the severe fire, and, when laid in good cement, has afforded a strong fireproof wall or pier. At least 4 ins. in brick was found necessary, and a layer of concrete 3 ins. in thickness between that and the steel was a great improvement and served well to protect the latter from rust. But this method will probably not be followed in general, on account of weight, bulk and expenses. Hollow brick and tiling were efficient, also, when properly and liberally used, as well as correctly applied on a good system. It has fireproofed satisfactorily; porous tiles proving
RESIDENCES FOR EARTHQUAKE COUNTRIES,
to be the better. In a country subject to earthquakes, a strongly-framed and well-founded wooden house, two, or at most, three stories in height, with non-disintegrating plaster and finish, light tile-chimneys and ample fire-prevention and protection is the ideal type of residence structure. The high steel-frame office buildings have shown that, in order to resist perfectly the bending moments and shears induced by the swaying due to earthquake movement, such buildings should be stiffened in their joints and connections by the best riveting combinations and knee, and other bracing, particularly at or near the ground floor. Columns, exterior and interior, shoidd be put in more liberally in future, upon the first and second stories, and the strongest joints and connections should be adopted, in order to resist the bending and shearing. With
HIGH STEED STRUCTURES.
such strengthening, the high steel structures will safely endure an earthquake of even greater severity than that of April t8, 1906. This kind of building has proved its worth and reliability and has come to stay. It has been tried and has not been found wanting. Minor improvements, as advocated, will produce a perfect structure. Concrete and reinforced concrete have become popular for construction with a large number of designers in San Francisco, on account of the claimed strength, indestructibility, facility of use, and fire and rust protection their materials afford. Unfortunately for San Francisco, there were few structures of concrete or reinforced concrete in the city at the time of the great trial; but these few behaved well, during both the earthquake and the resulting fire. Therefore, although such structures are admittedly new and comparatively experimental on the Pacific coast, the confidence reposed in them has already led to the designing of a number of large buildings of this type for public or business purposes. At present the sentiment is to limit them to a height of six or eight stories, 011 account of their experimental character, and because of the fear that greater height would permit a reversal of stress, due to earthquake and wind-force in the reinforced girders. Mill-construction, with brick, will undoubtedly be utilised in many instances for a considerable time to come; but the lesson taught 11s should be learned—that the materials used should be firstclass pressed brick, well-wetted, and cement-mortar, and that all parts should be thoroughly tied and anchored together. This rule has been found by experience to be a most important one to follow’, in all brick and stone construction, and its neglect in the past has re-
DIRECT CAUSE OF SAN FRANCISCO DAMAGE.
suited in much loss and ruin. The damage inflicted upon San Francisco from the direct and immediate effect of the earthquake was relatively small, being estimated at from three to ten per cent, only of the total loss; but the subsequent and indirect effect was to paralyse the water supply and its distributing system, start a great conflagration, render impossible its extinguishment with the means at hand, cause the death of at least soo human beings, burn approximately $500,000,000 worth of property, render houseless, homeless and miserable, 200,000 people, and inflict remoter damages to business, commerce, and labor, only to be estimated in the future. When it can he seen plainly, as is possible, looking backwards, that nearly all of this destruction and suffering might have been prevented by wise foresight and provision, it is felt that a warning must be sent to all tlv* cities of the world. Any city that disregards this warning will be guilty of a great crime. Of a build-
RISK ON BUILDINGS.
ing’s entire fire damage, the risk from fire within the building is estimated, on the average, at forty per cent., tile other sixty per cent, of the risk being from the exterior of the building. This risk for interior fires should be reduced to a minimum by ample provision for fire prevention. As far as practicable, the absence of combustible material should be secured. While the danger from exterior fires to a given building is ordinarily estimated at sixty per cent., it practically becomes 100 per cent, in case of a great conflagration. In San Francisco, little protection from exterior fires has been adopted. Many of the best buildings, had they been furnished with metallic shutters of the best design, with wiregass in metal sashes, and with cornice and other exterior sprinklers, supplied by a private water plant, certainly might have been saved. San Francisco’s experience recommends that wells and elevator shafts, running up through many stories, should be guarded by brick or reinforced concrete walls, fitted with double-metal rolling doors, bolted to the walls to allow the expansion; or with automatic sliding doors and wire-glass partitions. The importance and value of real protection will be appreciated, when it is stated that a third-class building, with such complete fire-prevention plant, is insured for less than a first-class one, not having it. This lesson is one that should be taught to all capitalist owners by their architects and engineers. Moreover, all parts of an establishment should be equally pro-
tectvd, for the fire may begin anywhere. Concrete floors with metallic-mesh reinforcement are strongly recommended for strength and fireproof character. A non-inflammable substitute for woodwork and trim generally is greatly to be desired. Double windows of wdre-glass in hollow metallic frames are recommended; or, where such material would be objectionable by cutting off the view, double-plate glass is considered next best. Interior doors should t>e of metal, or, at any rate, metal-covered in fireproof buildings, and the light for corridors and halls should come
WIRE GLASS AND ROLLING SHUTTERS,
through wire-glass. As the installation of wireglass, metallic rolling shutters and metal sash is only a small percentage of the cost of the building, and has proved to be such excellent fire protection, when of the best material and workmanship, a wise economy demands its use in every important fireproof building. Capitalists and owners must understand that perfect fire protection for structural steel is necessarily expensive. Any so-called fireproofing that is cheap or flimsy, is a delusion and will not serve. The application of an effective method insures permanence of the structure and at the same time is a reducer of the rates of insurance. Steel columns may be well fireproofed by surrounding them with four inches thickness of the best quality of stone or cinder concrete, or by three inches thickness of either, when hollow tiling is put upon the exterior. Three-inch porous terra-cotta tiling, wrapped on the outside with wire, and metal mesh used round the bed course of the column, has proved efficient. The mortar of the tiles should contain a large percentage of cement, and they should be strongly anchored to the columns to prevent their falling away in earthquake or fire and so leaving the steel exposed. In the great fire, decorations, trim, inflammable oil paints and varnishes, in office build ings aided materially in spreading the flames. A water color paint has been recommended that will
FIRE WALLS OF BRICK.
endure washing and is non-inflammable. Fire walls of brick, extending up above the roofs of buildings were effective in resisting the spread of the fire; Imt the support derived from metal bands and anchors was often neglected, like much other masonry in San Francisco, and such walls, therefore, fell, in many instances, both during the earthquake and the fire, particularly when laid in common mortar. Cast iron columns, in many buildings, endured the ‘quake and the fire quite well, but undoubtedly would have been broken or shattered, had cold water beet) thrown upon them in the midst of the great heat. Structures made of concrete blocks were usually greatly damaged or even ruined by the earthquake, owing to imperfect anchorage and failure to cohere at their joints. Granite, sandstone and marble were badly cracked and spalled bv the fire, the latter stone often crumbling to powder. A proper foundation, stable and firm, is of vital importance, and particularly in the case of soft, marshy or made ground. Anchorage, bonding and tying of
HEAVY STEEL FRAMING.
all masonry should be strictly practised. Steel framing should be made heavier rather than light er, and joints, connections, bracing and floorings should be strongly united. Girders and columns should be made very stiff, and. where practicable, continuous fireproofing should be of the most perfect type, and no reasonable expense should be spared in its installation. The lessons taught by the great fires of Boston, Chicago and Baltimore have been verified in San Francisco’s experience. In addition to these lessons, the following conclusions may be drawn; () Roofs, roof appurtenances and skylights should be given ample protection against fires from with
FIRE H08E AND APPARATUS.
out: (b) a great excess of lire hose and apparatus beyond ordinary needs, should be available; (c ) a strong bond for fireproofing tiling, etc., both for girder and column protection is essential; (d) protection for front windows as well as for side and rear ones, is of vital importance; (e) good protection for steel frames and steel roof-trusses in attics or the exposed or unusual places should be provided; (f) liberal use should be made of fire-retardent in windows and door transoms; (g) wise and liberal use of concrete and reinforced concrete for girder and column fireproofing has proved its saving quality; (A) interior fire protection and prevention by wells, pumps, sprinklers and water tanks vastly lessen fire-risk.’’ Captain Sewell also places himself
8TBEL FRAME CONSTRUCTION,
on record in favor of the steel-frame type of construction for tall buildings; but it should be thoroughly braced. “In my judgment (continues Captain Sewell) to secure the best results, the steel construction should also be inclosed with walls of reinforced concrete. The proper artistic treatment of this material would seem to be a very important problem for the architects in a place like San Francisco. Its great utility in earthquake shocks cannot he denied. Where steel frame buildings are to be finished with ordinary masonry walls, however, complete bonding of all face-bricks with full header-courses should be absolutely required; no other form of bond is adequate. Nothing but Portland cement mortar should he allowed in any portion of the structure. The masonry should be tied to the steel frame in the very best possible way, and much more securely than is ordinarily the case. For buildings of moderate height—say, up to 125 ft., as an extreme limit, reinforced concrete alone can undoubtedly be so designed as to give very good results, when subjected to either earth
REINFORCID CONCRETE BUILDING,
quake or fire. But the bracing of a reinforced concrete building of any height to resist earthquake is a matter for serious study. The problem can be solved; but it has not been solved as yet. Any building of considerable height in an earthquake-country should have as Tittle mass in the’ superstructure as possible. For the ordinary commercial building, where brick walls and wooden joists would ordinarily be used, I am of the opinion that reinforced concrete is the safest and most practicable solution in a place like San Francisco. Where reinforced concrete is used throughout, whether the building is very tall or not, great care should be taken with the design and execution of the connections between columns and members of the floor system. There should be heavy knee-braces for the connection of all girders and beams, and, wherever possible, portal bracing in the shape of reinforced concrete arches should he introduced. Of course, the amount of this work that needs to he done depends upon the circumstances in each individual case, such as the height of the building, its horizontal area, the kind of material, the dead weight in the upper stories, etc. It seems justifiable to conclude that a solid monolithic concrete structure of any sort is secure against damage in an earthquake-country, unless it should happen to lie across the slip. The Baltimore and the San Francisco fires, as well as manv other fires
COMMERCIAL FIREPROOFING INADEQUATE,
and fire-tests, have proved conclusively that commercial methods of fireproofing are inadequate to stand any real test. In the majority of cases, the steelwork is fairly well protected; hut the number of failures is sufficiently great to show that the factor of safety against fire is not by any means what it should be. For the protective covering itself to suffer complete or almost complete destruction in any one fire is in itself a failure, because, if it is brought to any such pass, the steelwork is very near destruction, and the margin of safety is altogether too small. In my judgment, columns should be covered either with 4 ins. of brickwork, laid in Portland cement mortar, and with all the interior space filled with concrete, or else they should lie inclosed in an expanded-metal basket and the entire interior filled with concrete, so that the minimum thickness of the concrete shall not, in any case, be
PROTECTION OP FLANGES.
less than 4 ins. Kxposed flanges of girders should he protected by the equivalent of from i}4-in. to ajki-in. of solid porous terra cotta, according to circumstances. If concrete is to be used, its thickness should be increased by about half an inch. The protection for lower flanges should always be inclosed in a basket of expanded metal or heavy lath-wire, securely anchored into the side protection of the webs. The San Francisco fire showed that, even in a hot fire, such metalmesh basket-work will largely retain its tensile strength, and thus hold in position the fireproof covering inside of it, even though the latter should IKshattered by expansion-stresses, or otherwise. The webs of girders should be covered by 4 ins. of brickwork or concrete, built up on the lower flanges. Girders should he completely covered from bottom to top before the floor-systems are put in, so that the collapse of
SOLID FLOOR BEAMS.
the latter will not expose the girder. Floor-beams should have solid, protecting skew-hacks, not less than t’/i-in. thick, or be covered with at least 2 ins. of concrete. In important work, the protection of their lower flanges should also be inclosed in expanded metal or wire-lath. The furred ceilings so much used in San Francisco are a valuable addition to the fire-resisting qualities of the floor construction, and. if the furring rods were more firmly secured, the total loss here, as a rule, would be measured by the value of the plaster alone. Hollow-tile partitions should never be less than 6 ins. thick. The results at Baltimore ami San Francisco did not, by any means, indicate that either hollow tile or concrete is altogether a failure or altogether a success. Both fires indicated very clearly that commercial methods of applying both materials are inadequate; lx>th also indicated very clearly that successful results can he attained with both materials. A conflagration never yields comparative
RESULTS FROM CONFLAGRATION,
results; hut from such results as are available, I think there is no question that the best fire-resisting material available at the present time is the right kind of burned clay. By the right kind of burned clay is meant a good, tough, refractory clay, almost as refractory as fireclay, made into proper shapes and properly burned. Some commercial hollow-tile work is made of good material ; but, as a rule, that is the only good thing that can be said about it. As for concrete, there can be no question that good clinker-concrete, made of well-burned clinkers, Portland cement and sand is a very efficient fire-resisting material. It is better than anything else, except the better types of burned-clay products; but the form in which cinder-concrete is commercially applied, is, on the whole, no better than the flimsy hollowtile work with which it competes—in fact, it is
HOLLOW TILE BEAMS.
not certain that it may not be worse. If a hollow-tile floor, for instance, loses its lower webs, the damage is very apparent, yet, in the majority of cases, the floor remains true and capable of carrying considerable loads. Very often a cinder-concrete floor which is even more seriously damaged remains true, for the reason that the fire which damaged it, also removed its superimposed load before the damage was fully accomplished. A hollow-tile which comes through a fire in which its temperature has exceeded 700° or 8oo° Fahr. is inevitably damaged in all cases, owing to the dehydration of the cement, though it may seem undamaged to the casual observer. This property of concrete of maintaining a good face, in spite of very real and very serious damage, is likely to lead the layman into very dangerous conclusions. Consequently, this property of concrete construction may lead to equally dangerous practice. Inasmuch as concrete is inevitably dam-
IGH TEMPERATURE DAMAGING TO CONCRETE,
aged to a greater or less extent by the application of a high temperature, it would seem that, in all cases where reinforced concrete floor construction is used, a furred ceiliflg below it should be absolutely required. It should be added that attic floors and roofs should be as carefully designed to resist fire as any other part of the building. This is a thing that has rarely been done, and the experience of Baltimore and San Francisco show that it is absolutely necessary. While there is no doubt that commercial standards of fireproofing are dangerously inadequate, the greatest trouble of all is the fact that so little attention is paid to protecting the exterior openings in a building. In my judgment, windows protected in the following way, even without sprinklers, might keep out the fire, evc-n though the building were shut up and abandoned. Protect the outer opening with some form of rolling steel shutter or, preferably, with a shutter composed of sheets of steel sliding in very deep rebates by means of angle-irons or rivets, driven so as to interlock with a bead to he placed in position after the sheet of steel is itself in position. By providing a pocket in the masonry just above the window head and making these shutters in three or four parts, overlapping and interlocking at the overlap, the whole shutter could he slid up into the wall practically out of sight. This
would necessitate window openings slightly lower than those often used in commercial buildings; but the loss of light would not be very serious. Make the windows entirely of wire-glass, sheetmetal, or metal-covered sash, hung in metal, or metal-covered frames. On the inside of the window, use a sliding shutter, either of wood, covered with sheet-metal, or else, of sheet-metal such as that for the outside.” In summing up his views on the situation, Richard L. Humphrey says; “The San Francisco disaster demonstrated that the lessons from the Chicago and Baltimore fires are still unlearned. The same faults in construction continue to be repeated. The only sure way to remedy grave defects of this character is to enact strict building laws, which will compel an observance of the essentials for fireproof structures. Large conflagrations demonstrate that there is no such thing as a fireproof building. To label one as such is bad practice, since it gives a false sense of security and causes a relaxing of necessary precautions. The lessons taught by the great calamities such as have befallen San Francisco, Baltimore and other cities, are not regarded. It is quite probable that the new San Francisco will to a large extent be a duplicate of the former city in previous defects
DEFECTS OF C0NS1 RUCTION.
of construction. The defects of construction which arc so strongly condemned by reason of their failure are no worse than those generally practised throughout the United States. The same defects are common, and it is evident that the same results would follow an earthquake of equal intensity in another part of the country. A moment’s consideration will show that the loss of life and property in New York, for example, under similar conditions, would be enormous.
PROPERTY DAMAGE OF SAN FRANCISCO.
The damage to property in San Francisco is estimated at $250,000,000, but this sum, large as it is, is exceeded by the total expenditures for new construction in New York. In three days, the tremendous area of over 2,593 acres was burned, destroying entirely 490 city blocks, and, in part, thirty-two blocks. Of this 314 acres comprised the congested district’ on which there was $250,000,000 insurance, probably representing a value of $500,000,000. In the Baltimore fire 1,343 buildings were destroyed, having an assessed value of $12,908,300. In two years these burned buildings were replaced by 570 buildings, whose assessed value is $20,000,000. These new buildings are larger that the old, and the widening of the streets has eliminated 700 building lots. It is expected that, when the reconstruction within the burned district is complete, there will be less than 800 buildings, of which the assessed value will be fully $25,000,000. It is, therefore, quite reasonable to suppose that the assessed value of the reconstructed San Francisco will be at least double that at the time of the catastrophe.
FEW CONCRETE STRUCTURES.
While reinforced concrete structures were few in the zone of seismic disturbances, these stood the test in a highly satisfactory manner. Rigidity and stiffness, and a high fire resistance, which are inherent qualities of concrete, demonstrated how admirably it is suited to resist this extraordinary test. . It is evident that in earthquake-countries, water-supply pipes at least should be so laid as to avoid the action of slips, s ttlements or grouTidmovements of all kinds. The pipe-lines should also be arranged with gates and bypasses, making it possible to cut out that portion of the system which is crippled. There should, also, be some means of preventing the loss of water which is occasioned by breaks in the house service pipes. The early failure of the water mains rendered the city helpless and placed it at the mercy of the flames, the fury of which for three days threatened to complete one of the greatest disasters of recent years and to obliterate one of the most beautiful cities. It was finally checked b.y a combined influence of a change in the direction
PROPER RARTHQUAKE STRUCTURE,
of the wind and a wide avenue. For a proper earthquake-proof structure, everything—the design, the materials used, and the workmanship— must he firstclass. Most of the failures resulted from bad design anti poor workmanship, and, in some cases, poor materials. The causes of the failures in San Francisco may be summarised as follows: (1) dishonest design and construction, especially as regards municipal, county and state institutions; (2) an effort, on the part of those qualified to design, and advise on building construction to meet the owners demands and erect structures for the least possible cost, which tends to a departure front the principle of correct design ;—the result was a structure that will carry ordinary loads, hut that fails, when subjected to unusual conditions. While two of the five sections into which the congested-value district is divided involve only a mile of conflagrating hazard within their own limits, they are badlyexposed by the others, in which all elements of the conflagration-hazard are present to a marked degree. Not only is the hazard extreme within the congested-value district, but it is augmented by the presence of a compact surrounding, great heights, large area, frame-residence district, itself unmanageable from a firefighting standpoint by reason of adverse conditions introduced by topography. In fact, San Francisco has violated all underwriters’ traditions and precedent by not burning up. That it has not done so is largely due to the vigilance of the fire deoartment, which cannot be relied upon indefinitely to stave off
HOTTER FIRE THAN BALTIMORE,
the inevitable. The destruction was greater, because the fire was hotter than was the case in the Baltimore fire, due, as has been pointed out, to the inflammable surroundings and the unprotected openings, and to the unchecked sway of the flames. The lower webs of floor-tile came off to, perhaps, a greater extent than in the Baltimore fire. It is said to be impossible to secure a suitable hard sawdust on the Pacific coast, such as is reciuired in the manufacture of the porous, terra-cotta tile. The tile used are, therefore,
FIREPROOFING QUESTION ONE OF DEGREE,
more dense and of poorer quality. The question of fireproofing, however, is of one degree, being dependent on the intensity and duration of the fire. A column may be properly fireproof for an office building, but entirely insufficiently fireproof for a warehouse; or a column, which may be all rignt for the upper stories, may fail in the basement, as in the case of the Kamm building. Buildings should be selfcontained, protected against exterior fires and capable of fighting fire from the inside, and, as in earthquake countries service is likely to fail, it is highly essential, where possible, to have an independent supply, as from an artesian well, with the necessary
THE USE OF DYNAMITE BAD.
pumps and service pipes. The indiscriminate dynamiting in San Francisco did more harm than good, for the reason that the concussions damaged the surrounding buildings, as in the case of the Post-office building, where the damage was extensive. The conditions at San Francisco were unusual, and, if the water supply had not failed, it is doubtful “whether it could have been controled for the reason that so many fires at a time would have made it impossible for the fire department to handle them efficiently, especially since there was such a large numb r of combustible, non-fireproof structures.” The reports of the three engineers show that, as a rule, the amount of damage to buildings in San Francisco varied according to the character of the materials and
RESULTS OF SAN FRANCISCO FIRB.
the class of workmanship. Buildings constructed of firstclass materials, with careful workmanship, suffered much less than those constructed of poor materials, with inferior workmanship. This fact should be a lesson to owners, engineers and architects in all parts of the country. In spite of all the lessons taught bv great conflagrations, it is to be deplored that a great deal of poor material and workmanship will enter into the construction of many buildings. Some of this is due to the desires of owners who want their buildings constructed as cheaply as possible and are willing to sacrifice quality to cheapness. Much of it, however, is due to the fact that information is lacking in regard to the use of many materials of construction. This is particularly true of concrete and reinforced concrete construction, the present rapid development of which is in its infancy, and emphasises the great need of addi • tional information in regard to structural materials. That the government is alive to this need is clearly shown by the work it is carrying on in its laboratories at St. Louis, Mo., where extensive tests and investigations of structural materials—principally cement, concrete and reinforced concrete—are being made. The results of this work will tend to establish on a safer and more practical basis, the claims of different types and materials of construction to their respective merits. ~~