BUILDING MATERIALS

BUILDING MATERIALS. The Indian peoples of North America had developed mature building techniques suitable to Neolithic cultures long before Europeans established their first settlements on the continent. In the eastern area of America, forests covered most of the land, and building accordingly consisted of gabled, domed, or vaulted frames built up of branches or light trunks and covered with bark, thatch, or wattle and daub. On the prairies the collapsible tent of nomadic tribes was constructed of a conical framework of saplings covered with skins. Permanent structures in the northern areas were circular, framed in substantial timbers, and covered with a thick layer of mud and grass for insulation against the cold and for protection against snow and wind. In the Sierras, where snow was the chief problem, steeply pitched frames of trunks and branches were covered with heavy slabs of wood rudely shaped from trunks split by wind. Variations on these structures, built with larger openings and covered with thatch, appeared in the warmer coastal areas.

In the deserts of the Southwest, where wood was scarce and heat insulation a necessity, the large communal structures known as pueblos were constructed in tiered series of rectangular apartments. They had thick walls of adobe (sun-dried brick) and roofs composed of branches laid on transverse log beams and covered in turn with a heavy blanket of clay. In the canyons of what is now northern New Mexico and southern Colorado, clays suitable for brick were scarce, but there were extensive outcroppings of sandstone that could be easily broken off into building stones. The Indians who penetrated the canyons constructed their pueblos of thin sandstone tablets laid either on the alluvial floor or on shelves and notches eroded in the canyon walls.

The Europeans who established the North American colonies in the seventeenth century brought their knowledge of materials and techniques from their native lands, but during the first few years of settlement they were often compelled to adopt Indian techniques. The English, Dutch, German, and French who settled the seaboard and Gulf coast areas brought variations on framing in sawn timbers. Frames were usually covered with clapboard siding for walls and shingles for roofs—the latter gradually giving way to slate and tile in the more elegant houses, especially those built by the Dutch. Construction in thick wooden planks set vertically came to be common in parts of the Connecticut Valley, while construction of solid walls built up of horizontally laid logs was introduced by Swedish settlers in the Delaware Valley. The only stone in these early structures was confined to foundations and chimneys. Joints were originally the mortise-and-tenon form secured by wooden pegs, but handwrought nails began to be used early in the seventeenth century and machine-made varieties in the late eighteenth century.

In the more costly forms of buildings, brick laid up in lime mortar slowly replaced timber construction in the English-speaking areas, but expensive stone masonry was confined largely to the Dutch settlements of the New York area. The domed and vaulted construction of eighteenth-century mission churches required kiln-baked, stucco-covered brick, which was stronger and more manageable than the adobe brick, widely used in the Spanish Southwest. All of the traditional European building materials were used throughout the nineteenth century, although with some innovation. Heavy power-sawed timbers were used as posts, sills, girders, rafters, joists, and braces in buildings and truss bridges; deep laminated timbers of bolted planks were developed early in the nineteenth century for the arch ribs of bridges; thinner lumber, like the two-by-four, which was soon to become universal, became the basis of the light balloon frame invented in 1833. As the nation expanded, carefully dressed masonry work of both stone and brick began to appear in large and elegant forms.

Iron

The most far-reaching revolution in the building arts came with the introduction of iron as a primary building material. Although it was first used as early as 1770 in England, it did not appear in the United States until about 1810, and then only in the form of wrought-iron braces and ties for timber arch-and-truss bridges. Cast-iron columns were first used in Philadelphia in 1822, and the cast-iron building front combined with interior cast-iron columns was well developed by 1848. The first cast-iron arch bridge was erected in 1836–1839, exactly sixty years after the English prototype. The first iron truss, again composed entirely of the cast metal, was introduced in 1840. Cast iron, however, is relatively weak in tension and therefore had to be replaced by wrought iron for beams and other horizontal elements as buildings and bridges grew larger and the loads upon them increased. The wrought-iron roof truss was introduced in 1837 and the combination cast-and wrought-iron bridge truss in 1845, both in the Philadelphia area. Wrought-iron floor beams of a depth adequate to the new commercial structures appeared almost simultaneously in three New York buildings in 1854. The first, although unsuccessful, application of metal wire to the suspension bridge was made in Philadelphia in 1816, but this practice was not common until 1842, when a second wire-cable suspension bridge was completed over the Schuylkill River in Pennsylvania.

Steel and Concrete

The rise of the new industrial nation following the Civil War was marked by two fundamental innovations in building construction: the use of steel and concrete as primary materials. The first appeared initially in two bridges erected almost simultaneously: the steel arch structure of Ead's Bridge, built by James B. Ead at St. Louis (1868–1874), and the steel cables suspending the deck of John A. Roebling's Brooklyn Bridge (1869–1883). The history of steel in buildings is more complex. The first elevator buildings of New York and Chicago were constructed with masonry-bearing walls and internal iron columns. The iron frame was expanded and elaborated during the 1870s and early 1880s until all internal loads were carried on cast-iron columns and wrought-iron floor beams. The decisive steps in skeletal or skyscraper construction came in Chicago: the first steel girders were introduced in the Home Insurance Building (1884–1885), and the first all-steel frame came with the second Rand McNally Building (1889–1890). Certain of these pivotal innovations in framed construction were anticipated in the Produce Exchange of New York (1881–1884).

Hydraulic concrete, originally a Roman invention, was revived in the late eighteenth century. Composed of lime (as a cementing agent), water, sand, and gravel or broken stone aggregate, it is virtually unlimited in use because in its plastic, pre-set state it can be cast in any structural shape. The hydraulic property comes from the presence of clayey materials in the lime, and before the technique of artificially producing the proper mixture was developed, builders had to depend on a supply of natural cement rock from which the hydraulic lime could be made. The regular use of concrete in the United States began in 1818, when deposits of cement rock were discovered in New York during construction of the Erie Canal. The first poured concrete house was constructed in 1835, and the first of precast block in 1837, both in the immediate area of New York City. The American manufacture of artificial cement was established in 1871; the use of mass concrete in walls, footings, jetties, dams, and arch bridges spread rapidly during the remainder of the century.

Plain concrete must be reinforced with iron or steel rods in order to sustain tensile and shearing stresses. Although the first experiments in this novel technique were carried out in England, France, and Germany, the first reinforced concrete structure was a house built in Port Chester, New York, in 1871–1876. The leading American pioneer in large-scale commercial and industrial building was Ernest Ransome, who built the first reinforced concrete bridge in 1889 and developed mature forms of reinforced concrete framing during the 1890s.

Few entirely new structural materials were introduced after 1900, but ferrous metals emerged in various chemical and mechanical alterations. The twentieth century saw the revival of chromium steel for the skyscrapers of the 1920s and the adaptation of self-weathering steel to structural uses in 1962. The major innovation in methods of joining members came with the application of electric arc welding to steel framing in 1920. Aluminum made its initial appearance as a structural material in 1933, when it was used for the floor framing of a bridge at Pittsburgh, Pennsylvania. Its role expanded to the primary structural elements of a bridge at Massena, New York, in 1946. The use of stressed-skin construction, with aluminum as a sheathing material, came with an experimental house of 1946, although similar construction in thin steel plate had been introduced in 1928.

The materials of reinforced concrete remained unchanged but were used in novel ways with the coming of shells (1934) and prestressed members (1938). Wood returned to large buildings in the form of heavy glue-laminated ribs and beams, appearing in the United States in 1937. Tubular forms of steel and aluminum came with the first geodesic dome in 1947. Plastics as a sheathing material were introduced in two conservatory buildings in St. Louis in 1962, but their use as a structural material came only in the 1970s.

BIBLIOGRAPHY

Condit, Carl W. American Building: Materials and Techniques from the First Colonial Settlements to the Present. 2d ed. Chicago: University of Chicago Press, 1982. The original edition was published in 1968.

Friedman, Donald. Historical Building Construction: Design, Materials, and Technology. New York: Norton, 1995.

Simpson, Pamela H. Cheap, Quick, & Easy: Imitative Architectural Materials, 1870–1930. Knoxville: University of Tennessee Press, 1999.

Carl W.Condit/t. d.

See alsoAdobe ; Aluminum ; Architecture ; Bridges ; Cement ; Ferrous Metals ; Fortifications ; Housing ; Nonferrous Metals ; Skyscrapers ; Tunnels .

Building Materials

Sometimes a burglar or assailant enters or leaves premises through a window, via a roof or ceiling, or by breaking down or forcing a door. This can produce a range of wide range of trace evidence derived from the building materials used in that particular dwelling. Trace evidence is often invisible and will adhere to the clothing, hair, skin, and footwear of a suspect without the person being aware of it. Forensic examination of the suspect may produce evidence that can link the person to the scene of the crime through the presence of tiny amounts of building materials.

Forensic analysis of building materials covers a wide range of substances, such as brick, plaster, slate, loft insulation, glass , and wood. The broad principles for collecting and examining such materials are the same. The evidence has to be collected from around the site of entry or escape from the scene of the crime, by brushing, taping, picking with tweezers, or vacuuming. The samples need to be stored in a separate unused container and transferred to the forensic laboratory through a careful chain of custody . Examination of the suspect and his or her clothes for matching trace evidence of building materials has to be done with great care and preferably not by the same investigator who was at the scene of the crime. Otherwise, fragments of brick dust or glass, for instance, could be unknowingly transferred to the suspect.

Most building material trace evidence is in the form of fibers or dust. For instance, loft insulation is composed of glass fibers. The first step is to examine the material by eye, in good lighting, and then under a microscope. Various microscopic techniques are used to establish the nature of the material. In comparison microscopy, the sample is compared to known reference samples of various types of brick or plaster. The exact color of the sample can be established by microspectrophotometry.

There are various analytical techniques that can determine the chemical composition of a building material. Forensic scientists may use infrared spectroscopy , neutron activation analysis, or x-ray diffraction as appropriate. The analysis of building material evidence may tell the investigators a great deal about how an entry or exit to a building was made by a suspect. This provides a vital link in reconstructing the events before and after the crime took place.

see also Crime scene investigation; Crime scene reconstruction; Glass; Paint analysis; Physical evidence.