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Burnt Clay Construction at San Francisco.
by Charles H. Alden, Jr.

ONLY a personal investigation of the ruined city of San Francisco enables one to realize the extent of the destruction to buildings and property in the catastrophe of April 18, 1906. To the observer, the actual destruction will undoubtedly be found far in excess of any ideas gained from outside information. No other conflagration gives us a basis for comparison in extent of devastated area. Here practically an entire city was destroyed; the buildings remaining unaffected on the outskirts are so comparatively few in number and unimportant in character that they hardly affect our impression of the total disaster. Entering from the bay, the natural gateway of the city, and walking through the business thoroughfares, the ruined and desolated areas extend as far as the eye can reach. Here there is no "fire line" to mark the limit of destruction. The few buildings in the devastated area which have escaped stand isolated with only their shells intact, gutted by the flames, but bearing witness to the strength and resistance of modern building construction.

The burnt clay products are found to have been extensively used in various ways, very generally is connection with wood and other combustible construction. A first impression leads one to form the idea that these products have failed is their fire-resisting qualities. A further study of the ruins and consideration of the causes of the disaster modify the opinion to a belief that the material itself was not at fault, but that the wholesale destruction and various other kinds of damage were due to the unusual character of the destructive agencies and the very incomplete and misguided manner in which our knowledge of the art of fireproof construction has been practiced. We know how to build strongly with fire- resisting materials and in a practically fireproof manner, but the necessity of limiting cost and rushing the work to completion prevents our taking advantage of sound methods and building safely, as we ought to be compelled to do by the city ordinances. San Francisco seems to have been particularly lax in this regard. Combustible buildings have been built in the thickly settled portions of the city, and many of them are of recent origin.

The causes of the destruction of the city were three; - earthquake, fire and dynamite. The damage caused by each separately is at present impossible to determine. The earthquake was felt suddenly and continued intermittently with varying intensity for a considerable period. It was followed closely by the fire, and during and after the fire large quantities of dynamite were used on many of the buildings without apparent method. That the earthquake alone could have disastrous effect is evident from its action on the surface of the ground and from buildings known to have escaped the fire and dynamite. The effects of the shock, however, were found to be very elusive, one portion of a building being seriously affected while another portion entirely escaped injury. The character and actual effect of these shocks do not seem to be clearly understood; we can only say that firm ground and solid foundations were better able to resist, than the more plastic soil and filled-in land, which was seriously affected. The new Post Office building was in a locality violently shaken, the ground in front of it being raised and depressed, causing undulations varying from four to five feet from the horizontal. The building itself was but slightly damaged, some cracks appearing in the outside stonework and slight damage was done to the interior partitions, which are of terra cotta. The universal extent of the quake is shown in the wholesale destruction of chimneys in the surrounding districts.

The effects of fire on the brick and terra cotta structures are not easily separated from the destruction by dynamite. The fire-resisting qualities of modern fireproof construction have been tested in other conflagrations. That at San Francisco teaches nothing radically new as to the effect on the material, but its imperfect use is responsible in most cases for the disastrous consequences. Intense beat caused some chipping and discoloration to architectural terra cotta, but of all materials standing it is by far the best preserved. The exact destruction by dynamite explosion cannot be determined. Portions of buildings which were stated on good authority to have been intact after the fire are now reduced to ruins through the action of the explosive inside their own walls or in the neighboring buildings. Dynamite certainly had a disastrous effect on all forms of building construction in San Francisco. The effect on walls was similar to that caused by the quake as it produced cracks and scaling. Most of the buildings in the burnt area had bearing walls of brick with floors of timber construction. The falling of the brick walls was caused largely by the poor quality of the cementing material. In most cases the bricks were separated from each other merely by the shock of falling, showing little adhesion of the mortar. The Call Building is conspicuous among those that survived the ordeal. It was one of the best built in the city, being of terra cotta fireproof construction. It was structurally intact before the use of dynamite on surrounding buildings, and will be repaired, and ready for occupancy within one month from the date of the disaster.

Near the City Hall and Post Office is an eight-story brick building with terra cotta walls and floors in good condition. It is now being used for banking purposes. The columns are fireproofed by four-inch terra cotta blocks which were not properly anchored or wired in place and in some cases they have fallen off. Pipes are carried next to the columns inside the fireproofing. The terra cotta partitions are bonded to the column casings, and where partitions have failed the casings are torn from the columns. This method of column protection is noticed in other buildings, notably in the Crocker, a large granite and terra cotta structure in the heart of the burnt district. The floors here are of terra cotta tile of side construction and are well preserved; any structural damage that has been done is believed to have been the result of dynamite. The safe deposit vaults in the basement are uninjured and are in present use. The end construction method of laying the floor tile found in another building shows damage to a greater extent, but a comparison of the two methods is useless in this instance, for the two buildings were undoubtedly subjected to entirely different conditions.

Another method of terra cotta flooring is found in the Emporium, a large store building also in the heart of the burnt district. These floors are thin segmental arches with terra cotta covering enclosing the beam. The workmanship appears to have been totally inadequate, for the six upper floors have entirely disappeared, leaving portions only of the two lower ones in place. The column protection is also of the type mentioned before, and much of it has been shaken off. Two interesting terra cotta fronts remain standing in this portion of the city. They belong to a building of otherwise combustible construction built around a low frame building occupying the corner. This corner building has been entirely destroyed, and of the other building the fronts alone remain standing, chipped and blackened to a slight extent, but bearing witness to the incombustible quality of architectural terra cotta. Other isolated fronts appear in other portions of the city and are, in the main, fairly well preserved. One exception only was noted where the terra cotta was of a peculiar reddish color and did not seem able to withstand the action of the heat. In cases where stone was used, - granite being used to a considerable extent in the lower portions of the buildings, - the work is badly spalled.

Apart from the business center of the city, but still in the devastated area, the St. Francis Hotel shows interesting effects of the fire. It is thirteen stories high, built around a court, and faces a park. The two lower stories are of stone, the upper stories of brick, surmounted by a galvanized cornice. The stone is badly spalled and the cornice has disappeared, but the brick is left in good condition. The court is faced with brick, with no apparent tie to the backing, and has peeled badly. Inside, the structure is nearly intact, although subjected to a fearful heat.

Another hotel, The Fairmont, is six stories high, prominently situated on the slope of the hill to the northwest, a conspicuous landmark as one looks across the devastated area. This building was not completed at the time of the earthquake and fire. The lower story above the foundation is of granite and the portion above entirely of terra cotta. The outside of the building is in good condition, except for the spalling of the stone, and discoloration of the terra cotta, which can be easily removed. The inside tells a very different story. The column protection is of expanded metal and plaster. This method of protection is also applied to the beams in the floors. As a fireproof protection it proved of little value, for the columns have seriously failed, buckling into a great variety of shapes.

Although the causes which led to the ruin of the city are of a complex nature and present conditions somewhat confused, examples are clear of structural methods and details which should be avoided, and if other methods had been employed it is safe to say that the buildings would have a very different aspect, in spite of the serious destructive agencies to which they were subjected. The protection of columns by metal lath and plaster is inadequate, as shown in the Fairmont Hotel and many other instances. Terra cotta blocks built loosely around the columns and not secured in place may have resisted the fire in some instances, but a different condition would have been found if the columns had been actually built in solid, as is often required in other cities. This was done in some instances in San Francisco and the work was found to be intact.

The conclusion arrived at after the Baltimore fire, that metal ties for face brick were ineffectual, does not seem to have held in this instance, for here corrugated metal ties appear to have held the face brick securely. Probably conditions were entirely different, and it is difficult to form general conclusions in this case as in many others.

That better methods of building should be required is the obvious lesson to be drawn from the San Francisco ruins, and the people appear to be inclined to profit by it. How much they will profit will be shown in the new city which seems destined to be built in the near future. The man with the panacea for all building evils is on the spot, working overtime. Will San Francisco become the experimental ground for every quack idea, or will her people give to the world a new city, created from those materials and by those methods which give beauty and permanence?

The one lesson for all parties who are identified with the building interests of this country is, that sane and sound construction is the only real safeguard against calamities of this sort.

The position that San Francisco has occupied on the Pacific Coast is not to be gainsaid because of the catastrophe which has overtaken her, and brains and money will not be lacking to put her again in a commanding position. It is the belief also that the civic possibilities will not be so wholly ignored in this instances as they have been in the cities which have suffered so severely in the past. Furthermore, I believe this fire will open a way for an architectural opportunity such as the country has not witnessed before.

In San Francisco the opportunities will await the architect rather than the engineer. We do not need an engineer to tell us how to tie the architecture and the construction into one. We do need architects to properly treat the bones of our buildings, and the opportunity of rebuilding the city is distinctly one of architecture. We know by the best of evidence that the structures which were built upon honor and upon recognized sound principles suffered comparatively little damage from either earthquake or fire; and if, in the rebuilding, the people will only take the time to start right, will not allow themselves to be rushed into ill-advised rebuilding as was the case at Baltimore, will recognize the obligation of working out pretty carefully a general scheme before indiscriminate building permits are issued, the new city will have opportunities such as no other except Washington has ever enjoyed. And if San Francisco is to command the confidence of the investor, is to receive the money backing which is so necessary to all large building operations, it is absolutely essential that the first step taken shall be the deliberate study of the general problem.

It is hardly conceivable that San Francisco can quite dare to neglect the splendid opportunities of a field swept almost clean for new ideas. Many of the buildings, of course, are still standing. The location of some of the prominent structures is not likely to be changed, but whoever is interested with the task of mapping the city of the future ought to have a very free hand, and the new San Francisco need suffer very little from past inheritances if only the forethought is taken in time.

While the old city was developing the natural topographical lines were entirely ignored; the business quarter thrust itself out into the bay; streets were carried straight over almost impossible hills; and the most expensive portion was the poorest in natural advantages. The city was poorly planned and worse built. In the rebuilding the filled-in flats cannot be ignored and will again become centers of business, but in the reconstruction the fact should be borne in mind that these filled lands proved to be the most unstable sites for building operations, the earthquake doing far more damage there than on the main land. Consequently one of the first rules to be laid down should be that heavy buildings must be carried clear through the filling and down to a solid natural bottom. Anyone who is familiar with conditions in Chicago will remember how for generations the city was built upon a quaking bed of mud until General Sooy Smith had the courage of his convictions and carried foundations down to the rock. This is what ought to be done in San Francisco.

Beyond this, however, if the buildings of the future are to be safe against a recurrence of just such disasters the restrictions of height must be absolute and far more than they are at present. It is one of the inconsistencies of our business life that in these days of rapid transit and the telephone the tall building should have obtained such a stronghold, and in the rebuilding of San Francisco the aggregate advantage to the city as a whole will very likely be measured pretty fairly in an inverse ratio to the limit of height of buildings. The tall building construction enormously develops a small locality, while restriction of height forces building to spread over a larger area and benefits a greater number of owners. Quite aside from the aesthetic effect there is surely every good business reason for an extreme minimizing of the heights of buildings which are intended to resist such cataclysms as this.

It should not be assumed that the steel frame construction implies tall buildings. That type was adopted in the first instance as an economical constructive measure to reduce the amount of floor space given up to walls in the lower story. For a number of years the system has been developing towards a rigidity of all its members, and the necessity for an elastic construction has not always been considered. The earthquake shows how essential it is that buildings of this character in that geological neighborhood should be able to give without breaking, should have a certain degree of flexibility. In very few instances was the steel frame very materially damaged; but in many cases the envelope, whether of one material or another, was shaken loose or fell out as a result of distortion, so that the result to the building was nearly as bad as if the steel frame had been dislocated. We must in the future pay more attention to the tying of the envelope on to the frame. We cannot depend upon a rigid material. Anything approaching a monolithic construction, even though reinforced in the most thorough manner with steel, would be inadequate to properly resist earthquake. The ideal material would be one in which each piece is so designed or so tied that the whole would possess both strength and flexibility.

It is evident that in many of the damaged steel frame buildings too much reliance was placed upon the frame and not sufficient care was given to the masonry. Poor mortar, poor bonds, and a structurally weak material could never successfully clothe even the best steel frame. The envelope must be applied with the utmost care, and in all these buildings it is economy to use Portland cement mortar. This has been conclusively proved by the example of the Palace Hotel, which appears to have been built upon honor, of good bricks, laid in excellent mortar, and which stood the shock far better than some of the steel frame buildings.


A WRITER in the San Francisco Chronicle of May 18 says: "Engineers and others whose hastily pronounced opinions have flown into print are, many of them, representatives of, or interested in, concrete construction. Few people understand what concrete is or that in its use there lies greater opportunity for the use of inferior materials than in any other construction, and it is universally admitted that poor concrete is absolutely worthless. Honesty has not been the general policy of concrete constructors, and, unfortunately for San Francisco, the sand banks are too near at hand.

"The papers have been full of the statements as to concrete being the only material for properly protecting the steel in buildings, which are unfounded in fact. A hasty glance at the first floor of the St. Francis, which evidently is all that was given by the engineer for a concrete construction company, reveals the fact that concrete afforded protection to the steel columns of this floor, as intended. However, all the other floors of the St. Francis had the steel columns increased in hollow tile, and they are all standing and in perfect condition, except in two instances where the space was insufficient to encase with hollow tile of proper thickness.

"Any unbiased engineer who will examine the following buildings, the Chronicle, St. Francis, Mills, Crocker, Mutual Life, Union Trust, Claus Spreckels and James L. Flood, will agree in the opinion that in all of these buildings hollow tile fireproofing did its work of protecting the steel perfectly. The Fairmont is the most noteworthy example of the insecurity of concrete for protection to steel. Here the question arises, was the concrete fire-proofing of the best quality and workmanship? Granted that it was not, what building ordinances can enforce honest work?

"A city of the dull grayness of concrete would defy all laws of beauty. Why, then, should we strive for a beautiful city? Concrete does not lend itself architecturally to anything that appeals to the eye. Let us pause a moment before we transform our city into such hideousness as has been suggested by concrete engineers and others interested in its introduction."

The Brickbuilder
Volume XV, Number 5
May 1906
Published Monthly by Rogers and Manson
85 Water Street, Boston, Massacheusetts
pp 98-102
Gift to the Museum from Peter C. Mintun of San Francisco.

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