What it is. So called fire-proof buildings. The failure of the older forms of construction. The reasons why. Wrong choice of materials. Wrong ideas of the proper construction for manufacturing buildings. Economy of the system of slow-burning construction. Special features of the system. Construction of floors. Concealed spaces. Brick walls. Ceilings and wooden walls. Kalsomining. Compound beams. Care of main timbers. Wooden columns.

Much has been said and written and many millions of dollars have been spent in the effort to construct fire-proof buildings.

Buildings have been constructed almost entirely of iron, steel, and glass; magnificent in appearance and costing princely sums of money to erect. They have been popularly called "fire-proof," yet the burning of their contents, or the effects of the conflagration of buildings near them, have so warped, twisted, and bent the metal work of their construction as to leave them a mass of unsightly ruins, a veritable scrap heap of old iron and steel.

Fine buildings have been constructed of solid granite, splendid in proportions and costly in their erection, and that seemed designed to stand for ages. Yet the excessive heat from the burning of buildings by which they were surrounded, and the action of the water from the firemen's hose on their heated surfaces, have practically destroyed them.

And in fact, in a great many cases less prominent than those above mentioned perhaps, expensive structures, apparently impregnable to the destructive action of fire, have fallen a more or less easy prey to the first serious conflagration that assailed them, and the hopes of their well meaning and conscientious designers have been doomed to disappointment, and their owners to those serious losses which no amount of insurance ever covers.

Such have been the results of the patient and really able efforts of many conscientious architects. Nor have the efforts of these builders in the past been more astray on the matter of materials with which to construct buildings, to resist the ravages of fire, than in the matter of form and detail in designing them, not only to be safe from fire, but practically useful for the purposes for which they were intended.

1The information necessary for describing and illustrating the type of buildings known as "Slow-burning" has been derived from the excellent reports of the Insurance Engineering Station, Boston, Mass. under the able direction of Mr. Edward Atkinson, an acknowledged authority on this subject.

Of the older construction of buildings where more attention was sometimes paid to appearances than to practical usefulness, and roofs were built in such ornate style and so ornamented with turrets, peaks, and dormer windows as to be hardly recognized as manufacturing buildings, it is gratifying to know that they are now things of the past, many of them having been destroyed by fires, invited by their faulty construction, and the wisdom thereby gained by costly experience preventing their reproduction.

But after years and years of the study and effort of many good men in this field, it is still an open question whether we shall ever get to the point where we can construct a building adapted to the practical wants of manufacturing operations that we can say is really fire-proof.

Such being the result of so much effort and expense in seeking for that which has, thus far, not been attained, it would seem wise to rather lower the standard of what is aimed at, and, instead of striving to build actually fire-proof buildings, to endeavor to design the best form of a slow-burning construction.

In so doing we will do well to remember some of the more important things learned by the experience of the past.

While it is doubtless true that many of the so-called fire-proof buildings might also be denominated slow-burning, yet it is also true that slow-burning construction, as now generally understood, is of a much more economical and simple form, and in a large majority of cases consists of wood and brick, and sometimes of wood alone.

To such an extent is this true that many of these buildings are constructed, the several stories being taken into the account, at a cost of less than eighty cents per square foot of floor surface, while the factor of safety is very high.

It has been amply proven that while a steel post or column may be sprung so badly during the early stages of a fire as to fail to sustain its load, a wooden post would not be burned through, but would continue to perform its office.

Wooden beams that in a protracted fire may burn through and allow the floor to drop, will ofttimes not do as much damage as is caused by the twisting of steel girders, which, becoming distorted, force other parts out of place and destroy portions of the walls on which they rest.

The special features of slow-burning construction may be said to be: so disposing timber and plank in heavy, solid masses as to expose the least number of corners or ignitable projections to the action of fire, and in such a manner that when fire does occur it may be most easily reached by the water from the sprinklers, or from the firemen's hose.

When several floors are necessary they are separated as much as possible by automatically closing hatches for elevators, by protecting stairways with non-combustible partitions, by avoiding light wooden partitions as much as may be, and by avoiding varnish or other rapidly burning finish on ceilings or floor timbers.

Floors should not be supported in the usual manner by joists placed closely together, but should be constructed of 3-inch planks, supported by beams placed about 8 feet centers. This will give free play to the water from the sprinklers, or the sweep of the water from the fire hose. It is a fact that in buildings having deep floor joists, placed closely together, one side of these timbers may be actively burning while the water is pouring on the opposite side.

Care should be taken to avoid concealed spaces where fire may exist and water from a hose or the sprinklers may not freely enter.

Brick walls should not be covered or sheathed with wood, and in cases where this cannot be avoided, the spaces between the wall and the sheathing should be as small as possible.

Ceilings, or wooden walls, may be effectually protected by covering them with expanded metal, wire lath, or dovetailed laths, and plastering with a hard, plain lime-mortar, which is sufficiently porous to permit the seasoning of the woodwork to which it is attached.

It is better to avoid the use of oil paint or varnish entirely, on the interior of manufacturing buildings, on account of its retaining all of the moisture that may happen to be in the wood, and so hastening the process of decay. Kal-somine, whitewash, or the water paints, so-called, are porous and consequently allow the seasoning process to go on unimpeded.

But as a rule, timbers may be left unprotected except in places very dangerous on account of fire, since any fire which will seriously impair or destroy a heavy timber will already have done its work by destroying other and lighter parts of the structure.

In many instances it may be desirable to substitute compound beams for single timbers. These are made by placing two or more beams or planks side by side and securing them by through and through bolts. It is frequently easier to obtain well-seasoned lumber of the smaller dimensions, and any weak place in one is supported and reinforced by the other when secured to it. Ordinarily the thickness of such timbers should be from one third to one half their width. In building up a compound beam, the separate timbers should be placed slightly apart, so as to permit ventilation to their surfaces, and thus render them less liable to decay.

The main timbers should not be cut into more than is absolutely necessary for securing braces, the support of horizontal timbers, and for similiar purposes, as the timbers are very materially weakened by even a slight cut. For the same reason, no more holes for bolts, rods, etc., should be bored in the timbers than is really necessary to fasten them together, or to aid in supporting other timbers. Holes used for bolting together compound beams should be located, not opposite each other, but in a zig-zag form.

Wooden columns or posts should have a hole, say one inch to one and a half inches in diameter bored through their entire length, and then connected with the outer air by two half-inch holes bored through the column near either end. By this method, the moisture originally contained in them may have an opportunity to evaporate.