The Monadnock Building was built during a period when bricks were the building material of choice. Bricks are easy to manufacture, they are cheap and versatile. There was one problem, however, with bricks—they are very heavy. If you make a building too tall with bricks, it will collapse under its own weight. Modern buildings, hence, use columns and beams made of reinforced concrete or steel to bear the weight. The walls are merely curtains to keep the elements out.

In the 19th century, the steel industry was still in its infancy experimenting with different forging techniques but none was suitable for making construction-grade steel. Then in 1856, an English inventor named Henry Bessemer showed how to make steel economically, and for the next one hundred years, the Bessemer process was the leading industry technique driving of up steel production and leading to steel being widely substituted for cast iron.

The Monadnock Building was designed by John Root of the famous firm Burnham & Root, and built over a period of three years from 1891 to 1893. At sixteen stories, it is the tallest load-bearing brick building ever constructed. The building is so heavy that the walls at street level are six feet thick making the ground floor dark and gloomy like a dungeon. The walls taper as the building rises, so higher floors are more spacious. Even at the top, the walls are 18 inches thick.

The decision to build such a tall building using only bricks was surprising, because Chicago’s soil is famously swampy. One New York Times reporter described Chicago’s soil as “a great jelly-cake” with a “semi-fluid” layer like “molasses.” Anything heavy built on such soil attempts to sink.

To arrest the building from sinking too much, engineers built a concrete raft reinforced with railroad rails under the building so that the weight could be distributed over a larger area. This raft extends eleven feet beyond the building in every direction, but even with the raft, the Monadnock Building sank almost two feet after construction. This was more than the expected eight inches. Consequently, the ground floor is located a step down from the street level.

The fact that the building still stands is a testimony to the skills of John Root, who unfortunately, didn't live to see the building completed.

To be honest, the Monadnock Building is not entirely made of bricks. Aside from the iron raft, a hidden framework of cast and wrought iron braces against the masonry walls from the inside so that the building doesn’t topple over during high winds. This structure merely provides lateral support and doesn’t bear the actual load of the building. This was the first time wind bracing was used in a building in America. The Monadnock Building is also the first to feature aluminum in building construction. An exotic and expensive material at the time, aluminum was used to build its decorative staircases.

Encouraged by the building’s success, the owners acquired the adjacent lot to the south and built an extension. The southern part uses a steel-frame construction instead of load bearing walls, making the Monadnock a unique amalgamation of two different building tradition. Because the southern part is steel-framed, the walls are much thinner allowing for more rentable space than the northern half. Once completed, the Monadnock became the largest office building in the world, with 1,200 rooms and an occupancy of over 6,000—larger than the population of most Illinois towns in the late 19th century. It was the first building in Chicago wired for electricity, and one of the first to be fire-proofed, with hollow fire clay tiles lining the structure so that the metal frame would be protected even if the facing brick were to be destroyed.

The Monadnock Building today finds a place on both the National Register of Historic Places and the National Historic Landmark.


According to amusingplanet