Frames

Although wrought iron was exploited relatively quickly for girders, vertical support continued to be provided by walls or cast iron columns.

By the 1860s wrought iron rollings were already being used to construct the floors of buildings with brick arches spanning between them. It was still convenient and common to use cast iron columns for the vertical supports, although these buildings also relied upon masonry walls to carry a proportion of the load. These walls also provided stability; and were either masonry exterior walls (in wide deep buildings) or masonry party walls (on narrow buildings) possibly with non loadbearing cast iron fronts. A few cast iron fronted buildings were constructed in Europe but they were more common in America where examples can still be seen in cities like New York and Baltimore.

These buildings preceded the use of cast iron fronts in Glasgow and Liverpool, but it is interesting to note that in London this form of construction was forbidden by building regulations.

The possibility of higher buildings became a reality with the parallel development of the passenger elevator.

Some of the important milestones in the development of passenger lifts and the influence on the construction of higher buildings are listed below:

• The Albert Dock buildings in Liverpool were equipped with hydraulically powered hoists.
• In America, the Bunker Hill Monument was opened in 1844 with a steam driven hoist
• There was a passenger elevator in the observatory tower of the New York Exposition of 1853.
• The Haughwout Store New York in 1857 had the true forerunner of the modern elevator for commercial buildings (by Otis).

Whatever the structural possibilities of this form of construction its commercial use was limited by the willingness of the building's users to climb many flights of stairs, five floors being the effective maximum. The possibility of higher buildings became a reality with the parallel development of the passenger elevator. Goods hoists had, of course, been used for some time. The Albert Dock buildings in Liverpool were equipped with hydraulically powered hoists and cotton warehouses in Manchester also had hoists. In America the Bunker Hill Monument, just outside Boston, was opened in 1844 with a steam driven hoist to take people to the top and there was a passenger elevator in the observatory tower of the New York Exposition of 1853. But the use of the elevator in commercial buildings dates from the installation of the device perfected by Otis in the Haughwout Store New York in 1857. Even then, it was not until the seven floor Tribune Building and the 9 floor Western Union Building (both built in 1869) that advantage was taken of this new invention to increase the number of lettable floors.

Examples of the move towards the multistorey all iron and steel frame include the Shot Tower, and the two Monadnock Buildings.

The Shot Tower, by James Bogardus in 1856, had an iron frame with a non-loadbearing cladding of brick. The advantage of the frame building over its masonry counterpart is most clearly seen by comparing the plans of the second Monadnock Building 1889-92 with that of the original Monadnock Building (1884-5), the last of the tall masonry buildings.

Both buildings had brick external walls and iron columns but in the first the external walls carried their own weight. The second Monadnock building has an increased plan area on the lower floors because thickening the walls at lower levels was no longer required.

Tall iron frame structures were beginning to appear in the last quarter of the nineteenth century before their general use in commercial buildings. Structures like the Latting Observatory Tower in New York (1853), the Eiffel Tower in Paris built in 1887, and the Statue of Liberty in New York (1886), were dramatic examples of frame construction. However, these examples were probably less relevant to the problem of tall buildings than that of the iron frame Shot Tower.

The change in the form of construction from frame mixed with external loadbearing walls to the complete frame building took place in several steps.

The first was the appearance of the complete frame building with columns on the external walls so that the masonry carried none of the floor loads. The relationship between the external columns and the wall might vary. They could simply stand against the external wall or be incorporated within it. With a complete frame building the height of construction was no longer limited by the ability of the wall to carry its own weight. Moreover, this also solved the problem of the differential thermal expansion of the masonry and the iron.

Jenney's Home Insurance Building, Chicago (1883-5) is generally regarded as the first building to have a complete steel skeleton, with the walls carried on angles attached to the spandrel beams between the external columns. Until the demolition of this building it had been assumed that the walls were self supporting.

Another landmark was the construction of the Tower Building in New York.

Designed by Bradford Lee Guilbert in 1887 it's thought to be the first to use skeletal construction. At the time it was so unusual that construction was held up until the following year while waiting for approval.