Monday, March 31, 2014


For millennia, the only way to build to build a strong building was to pile up lots and lots of stone or brick, forming massive masonry walls that could hold up the weight of the floors and roof. This ancient approach worked well enough as long as buildings weren’t more than six stories tall or so. If they were, the lower walls had to be made impractically thick in order to carry the weight of all that masonry above them--the more stories, the thicker the walls. 

By the late nineteenth century, when American engineers and architects began contemplating structures of ten, fifteen, or even more stories, the limitations of masonry construction reached a critical point. One of the tallest masonry buildings of this era, Chicago’s Monadnock Building of 1891, carried its seventeen stories of brick on ground floor walls six feet thick. Such a ponderous system simply wouldn’t do if tall buildings were to become practical. Fortunately, a new building material--steel--solved this problem just in time. 

Steel’s earliest ancestors date back at least four thousand years, but it was the invention of the Bessemer process in 1855 that first allowed it to be mass produced. Steel’s structural advantages were immediately obvious: Pound for pound, it was many times stronger than masonry, and just as important, it was equally strong under both compression and tension. Steel was also ductile and would bend under a heavy load rather than cracking. These attributes meant that a steel beam could support heavy loads and span long distances much more efficiently than any type of masonry, allowing even the tallest building to be supported by a relatively light “skeleton frame” of girders rather than by hundreds of tons of stone or brick. 

Steel members--including the familiar though now little-used “I-beam”--were typically riveted together (and later, bolted or welded) into a cage-like structure that carried the entire building load. Since the outer walls no longer had to support the weight of the stories above, they could be very light enclosures of glass, metal, or some decorative veneer--hence the term “curtain wall”.

The first tall building with a load-bearing steel frame was Chicago’s ten-story Home Insurance Building, designed by William Le Baron Jenney and completed in 1885. Engineers and architects quickly followed Jenney’s lead over the next few years. So sweeping was this change that, while the aforementioned Monadnock Building had marked the apogee of load-bearing masonry construction, an addition to it built just two years later was already being framed in steel.

Meanwhile, the price of downtown land in large cities all over America was beginning to skyrocket, putting pressure on developers to pack more volume into the same amount of real estate. That meant just one thing: ever-taller buildings. By the late 1890s, the new possibilities inherent in the steel skeleton frame, spurred by rising urban real estate prices and enabled by the invention of the safety elevator, had set off a national skyscraper boom that, for better or worse, is still with us today.

Monday, March 17, 2014


For millenia, the only way to create a strong, durable, and fireproof structure was to build it out of stone or brick. Needless to say, this required plenty of time, material, and effort, not to mention a lordly budget. But for most of man’s history, this tried-and-true ancient method had to suffice. 

There was finally a tantalizing glimmer of change in this situation toward the end of the 18th century, when a material long in use for other items--cast iron--began to be used in building. Pound for pound, cast iron was much stronger than stone or brick. Since it was cast in molds, it could be cheaply mass produced. And lastly, cast iron wouldn’t burn.

Among the first structural uses of cast iron was the celebrated Coalbrookdale Bridge across the river Severn in Shropshire, England, built by one Abraham Darby III in 1879, and still standing today. Darby came from a storied dynasty of English ironmongers who had cast cooking pots and like paraphenalia for generations. Darby reasoned that the same process might serve very well to produce repetitive structural members such as girders--and not incidentally create a vast new market for his products. 

Knowingly or not, Darby opened a whole new chapter in the history of building. Most of the structural innovations using cast iron came from engineers rather than architects, and most of these advances were made in Britain, the cradle of the ongoing Industrial Revolution. 

At first, cast iron appeared to be the greatest building breakthrough since ancient times. It began to be widely used in bridge structures and other civil engineering works. In architecture, cast iron columns and beams became common in factory and commercial buildings. Slender, delicately ornamented cast iron columns even appeared in a few large English manor houses. 

Alas, this promising future clouded over on May 24, 1847, when a brand new cast iron bridge across the river Dee in Chester, England collapsed. An inquiry determined that one of the cast-iron girders had snapped under the load of a crossing train.  England saw subsequent cast iron failures of the Bull Bridge in 1860, the Woolton Bridge in 1861, and finally the catastrophic collapse of the Tay Bridge in 1879, which killed sixty, including the bridge engineer’s son in law. In architecture, too, iron proved vulnerable. Unlike wood, which visibly bends when overloaded, cast iron could appear sound in one moment and shatter in the next. Most--er, ironic--it turned out that while cast iron wouldn’t burn, fire could still weaken it to the point of collapse.

After yet another bridge failure in 1891, it was determined that all cast iron bridges in the United Kingdom should be replaced. Future bridges were supposed to utilize wrought iron—a tougher, more malleable metal that unfortunately lacked cast iron’s ability to be molded. 

However, as so often happens in history, new developments soon rendered these plans moot. By the end of the 19th century, steel--a newly perfected material that was both strong and extremely malleable--was poised to revolutionize building. Cast iron continued to be used on occasion for prefabricated store fronts and the like, but engineering’s age of iron had ended. 

Monday, March 3, 2014


Now and then, you’ve probably heard people describe some interesting old house as having “good bones”.  But what do they really mean by this? What gives one house better “bones” than another? The answer lies in an aspect of architecture that’s little appreciated and even less understood: Composition. 

Many people assume that the way a house looks from outside is just the inevitable consequence of the room layout within. But this is a modern conceit brought on by the idea--equally modern--that “form follows function.” For all the modernist talk about buildings reflecting their internal functions, though, modernist architects were even more attuned to the need for artful composition than their predecessors were. They were fastidious in arranging the purportedly functional features of those otherwise stark facades--juxtaposing big window against small, high roof against low--to wring more drama out of their compositions. 

In truth, any architect worthy of the title will compose the exterior elevations of a house with painstaking deliberation--fussing with rooflines, or adjusting the size or location of windows or doors by a few inches here or there in order to get just the right balance of movement and repose. So few houses, whether traditional or modern, are bestowed with “good bones” just by accident--getting them to look that way takes a good bit of thought.

Ironically, the verdict on all this effort arrives in the few seconds after we first behold a building in the landscape. This is when our brains try to make visual sense of it and, as it were, give it a subconscious thumbs up or thumbs down. Since our brains find objects with a few bold elements more comprehensible than inarticulate jumbles, compositions with limited elements and a clear hierarchy of features seem more pleasing than those with lots and lots of competing elements. 

The fact that our brains tend to favor coherence over chaos doesn’t imply that buildings should be simplistic or have an absence of detail. It simply means that, no matter how complex they might be, their overall design should still feature a limited number of elements with a clear hierarchy. This concept holds true whether we’re talking about a one-room cottage or the Palace of Versailles. 

To prove the point, let’s distill these two extreme examples into a few phrases summing up the viewing experience. For our imaginary cottage, we might describe the sequence of visual impressions as follows: Big steep gable; lovely front door; towering chimney. As for Versailles, despite its enormous size and complexity, our initial impression might still boil down to just this: Imposing central block; powerful flanking wings; gardens stretching away. Both, we might finally decide, have “good bones”.

Architecture is of course far more complex these few brief impressions can possibly convey. Proportion, scale, symmetry, color, texture, procession, and a host of other concerns round out the experience of a great building. Yet labor as architects might on aesthetic minutae, if the overall composition doesn’t pass muster, the fine points--no matter how beautifully wrought--won’t make any difference. It’s the big picture that we judge in pronouncing a design pleasing or pitiable--as having good bones or bad.