Rising To Failure

by Don Friedman on October 3, 2017

This is the same building as the unlinteled door – it was chock full of bad masonry conditions. The picture above is just to provide some context. I’m interested in the brick pier in the cellar. Here it is in isolation:

There are several possible causes for the visible damage, but rising damp is the one that best fits the evidence. The cellar of a house is not somewhere you’d expect moving equipment that could lead to the impacts necessary to damage brick after brick; the site is on a hill with good drainage, so it’s unlikely that the cellar has flooded regularly.

The fact that the mortar is more or less intact while the bricks are turning back into clay and collapsing is good evidence that the mortar is portland-cement based. Deterioration of the building has opened up the cellar to the exterior air, which actually speeds up the deterioration: rising damp in a humid cellar is inhibited by the water vapor in the air. Rising damp moves faster in an area at ambient humidity, which is almost always less than that of an unventilated cellar.

Unoccupied buildings are more vulnerable to structural damage than buildings in use because there’s no one to complain about the first signs of trouble – leaks, jamming doors, warping floor boards, and so on – and because they no longer have ordinary heating cycles. Buildings that have had partial demolition (including finishes) or partial failure are much more vulnerable. The ordinary flow of water and air through the building is increased, the building is more flexible than it was before and therefore likely to develop new cracks in its exterior, the new load paths created by removal or old load paths may overload areas that were previously okay. This last item is of course the essence of progressive failure.

That’s a lot to pin on one pier with failing brick, but collapses have to start somewhere.

All In The Emphasis

October 2, 2017

I find this article in the New York Times about the recent earthquake in Mexico City to be problematic. To be clear, I claim no special knowledge of the quake itself or of Mexico City, but the building process is the same everywhere. To create a building of any significant size, we need a prospective […]

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Patterns of Damage

September 28, 2017

João Carlos Souza has a primer up on ArchiNet on how to identify problems in concrete buildings based on crack patterns. Putting aside some bad translation from Portuguese to English* it’s quite good and can help identify damage when used as intended. Mr. Souza does not explicitly state the assumptions that went into his visual […]

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Failure In An Expected Pattern

September 20, 2017

The animated picture above is from The General, a 1926 Buster Keaton movie. (Click on the picture to enlarge it.) In the era before computer graphics, and when the use of scale models for special effects led to disappointing results, Keaton got a realistic train crash in the obvious manner: he crashed a train and […]

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Anna Karenina in Concrete

September 10, 2017

Tolstoy said that “Happy families are all alike; every unhappy family is unhappy in its own way.” This principle can be applied to buildings: every building in good condition is alike, every failing building fails in its own way. The white paint on the concrete does a great job, in my opinion, of highlighting where the […]

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Sidewalk Vaults and True Obsolescence

August 14, 2017

For people unfamiliar with sidewalk vaults, the illustration above, from 1865, might seem plausible, but it’s actually Daniel Badger’s fantasy of how he could sell more iron. The left-hand side is reasonably accurate for mid-1800s vaults: the facade columns extend down past the plane of the sidewalk, marking the separation of the cellar proper from […]

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