MILL-CONSTRUCTION OF TO DAY
WOOD VERSUS STEEL BEAMS IN A FIRE.
COMPLETE DESTRUCTION OF A MACHINE SHOP AT CLEVELAND, WHERE LITTLE INFLAMMABLE MATERIAL WAS USED.
In a building of mill construction, in addition to the fire-walls, with standard fire-doors at each, there should be incombustible fire-curtains. These are made of metal lath, in the roof—say, of a machine shop, with cement plaster or galvanised corrugated iron. They must be substantially erected. They must fit tightly, and are best fastened directly to the side of one of the trusses and to angle-iron secured to the under side of the roof-plank. If doors are necessary to provide access to overhead scaffolds or for any other purpose, they must be fire doors and should be provided with sprinklers on the under side.
THE BUILDING MATERIAL.
should be either rcinforc e d concrete, or the structure s h o u 1 d be substantially built of hnrdburncd brick. If these columns are to be used inside, and for the protection of structural steel or wrought iron generally so that it shall not buckle or bend under the action of heat, which it will do much sooner than stone, beams or posts of wood, they must be protected by fireproofing—an essential in buildings of more than one story, so as to prevent a fire in a lower story from bringing down everything above it. One illustrati’ n that accompanies this article shows the results of a fire, where the stability of the single 8 x 10-in. wooden timber roof was not affected, although the 10-in. steel beams sagged and were twisted to a degree that required rebuilding. This wooden beam was used, because not enough steel had been ordered to complete the work promptly. In rebuilding, wooden beams were used throughout.
which has already been spoken of, but simply with respect to the form it should take in the case of certain buildings. For factories and buildings in general and especially those in which light is an essential requisite, the value of a perfect light is being appreciated more and more.1 he best style, of course, is one that combines both safety and light. This is obtainable by the employment of the saw-tooth roof, with wooden framing. Of such roofs two illustrations are presented. One shows the saw-tooth extension, with the application of the principles of reinforced concrete, showing also an ample window-area in the side walls, which not only provide all the light possible, but, also, assist ventilation. The other is an interior of the room under the same roof. The very excellent diffusion of light from the saw-tooth form or skylight will be noted, the steel channel, beams being provided only for the support of the shaftings, while the supporting columns are non-combustible. The roof-covering—an important item—is composed of asphalt and slag on 3-in. roof-plank (it should never be less than 3-in.), grooved for hard wood splines. The wooden sashes are fixed double glazed, with yellow pine beams 8 to 3 ft.In the cut the tension rods are about -o ft. apart, the beam-hangers bolted through girders and joint bolts for beams; wood columns; i-in. maple top floor, I-in. rough; intermediate 4-in. plank grooved for hardwood splines; floor-beams about 8 ft. on centre; concrete basement floor; wood columns; cast iron post cap cast iron cap. Observe following details
Roof covering, pitch of valleys—the pitch is obtained by nailing pieces of varying height; trusses 8 to 10 ft. on centres; steel truss; metal sash, double glazed; structural and steel columns. The steel columns will, of course, be protected by insulating materials, as the column is the vital part of the roof support.
WHAT MAY HAPPEN.
It may erme to pass that, in spite of w’hat may have been looked upon as being principally a slowburning construction of the true type, buildings, such as machine-shops, are burned. A11 illustration shows the results w’here the stability of the props of the roof and floors gave way, with disastrous results. In such a case the vaunted fire-resisting construction proved no safety at all. That w’as exceptional, and it may happen sometimes that, as in the building illustrated (a big machine-shop property several hundred feet long, with but little of a combustible nature in its con-struction, except the roofs, windows and flooring,) such a method of construction w’as a positive disadvantage. If, however, the mill-const-‘cted style of building is strictly and conscientiously followed, each construction and equipment should guarantee, so far as is possible, the safety of a structure of that type.
In such a case as the one here illustrated, the absence of .automatic sprinklers and of firestops of the large areas in the shape of fire-walls, with fire-doors, would account for the total or almost total destruction of such a building. Areas are, of course, necessary for economical shop management; but they should not exceed the limit needed for safety.
W’HAT MILL CONSTRUCTION IS NOT.
The late Edward Atkinson, who may be looked upon as the father, as to the end of his life he was the staunch apostle of mill-construction, putting some up as follows, what such construction is not.
“1. Mill-construction does not consist in disposing a given quantity of materials so that the whole interior of a building becomes a series of wooden cells; being pervaded with concealed spaces, either directly connected each with the other or by eracks, through which fire may freely ass where it cannot be reached by water.
“2. It does not consist in an open-timber construction of floors and roof resembling mill-construction, but of light and insufficient size in timbers and thin planks, without fire-stops or fireguards from floor to floor.
“3. It does not consist in connecting floor with floor by combustible wooden stairways incased in wcod less than two inches thick.
“4. It does not consist in putting in very numerous divisions or partitions of light wood.
“5. It does not consist in sheathing brick walls with wood, especially when the wood is set off from the wall by furring, even if there are stops behind the furring.
“6. It does not consist in permitting the use of varnish upon wood-work over which a fire will pass rapidly.
“7. It does not consist in leaving windows exposed to adjacent buildings unguarded by fireshutters or wired glass.
“8. It is dangerous to paint, varnish, fill or incase heavy timbers and thick plank as they are customarily delivered, lest what is called dryrot should be caused for lack of ventilation or opportunity to season.
“9. It does not consist in leaving even the best constructed building, in which dangerous occupations are followed without automatic sprinklers, and without a complete and adequate equipment of pumps, pipes, and hydrants.
‘‘10. It does not consist in using any more wood in finishing the building after the floors and roof are laid than is absolutely necessary, there being now many safe methods available at low cost for finishing walls and constructing partitions with slow-burning or incombustible material.
“It follows that, if plastering is to be put upon a ceiling following the line of the underside of the floor and the timber, it should be plain limemortar plastering, which is sufficiently porous to permit seasoning. The addition of the skim-coat of lime-putty is hazardous, especially if the topfloor is laid upon resin-sized or asphalt paper. This rule applies to almost all timber as now delivered.
“All the faults above recited have been committed in buildings purporting to be of mill construction, and all form a part of the common practice in ‘combustible architecture.’
“The foregoing description (adds the writer) of what slow-burning construction is not may be taken as a true description of what ‘combustible architecture’ is. It often seems as if the motive of this style of architecture had been to assure the most complete destruction of property by fire from the least and most preventable causes. Examples may be cited of what purport to be brick and stone churches, expensive residences and halls, of which the outer wall is only a sham, screening a very combustible wooden building, so pervaded by hollow wooden flues that in the case of fires, which often occur in the air boxes of furnaces and in the heating apparatus in the basement, the first notice is given bv smoke or flame from the peak of the roof.”
Newark, N. J., may appoint an additional battalion chief.