Patterns of Damage

by Don Friedman on 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 glossary of cracking, but they can be seen in is diagrams: he’s talking about modern** buildings with two-way slabs*** and spandrel beams. If the building has columns reinforced in non-standard ways as was permitted by code in as late as the 1920s, or has low-strength concrete as was common through the 1940s, or has one of the strange patented rebar systems that were in use through the 1910s, this guide may be inaccurate.

Those problems don’t mean that the guide is useless, of course. There are an enormous number of buildings which meet the unstated assumptions and for which it would serve as a good start on field investigation. The lesson, as always, is to start with the building at hand and then see which tool is appropriate for analysis.


* “Material retraction” instead of “shrinkage,” and “repression at the foundation” instead of “settlement” are not terrible and do not make it impossible to get the author’s meaning, but discussing engineering in non-technical language is difficult enough without using non-standard terminology.

** Or at least modernish concrete buildings that follow the basic construction and design patterns in use for the last fifty years or so.

*** Actually, this is a bit unclear. His diagrams for “Cracks on slabs due to insufficient positive reinforcement” and “Cracks on slabs due to excessive overload” clearly show flat-slab construction, but the small axonometric of the building seems to show beams on the right side more closely spaced than the columns. There’s a form of flat-slab construction that has beams on the column lines, but it’s unpopular because it combines the negative aspects of two-way construction with the negative aspects of beam and one-way slab construction.

Historic and Modern Structural and Non-Structural Detail

September 11, 2017

I hope the title is broad enough…I wouldn’t want to leave anything out. This is a probe in the facade of the penthouse of a 1920s apartment house. The exterior of the masonry facade has been stuccoed, which is why the background is so white. The pipe in the lower right corner is part of […]

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Anna Karenina in Concrete

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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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August 30, 2017

The front entrance of Castle Clinton in 1896: The front entrance of Castle Clinton in the 1970s: We’ve been writing a lot of conditions reports lately. Just coincidence, really: as a small firm, the type of work we have at any given moment can vary. Some months are more design intensive, some more construction intensive, […]

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An Added Benefit

August 27, 2017

We climb scaffold for a single purpose: to see some aspect of a building up close in order to better understand it. But a lot of the time (click on the panorama above to enlarge it) the view is worthwhile in itself.

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Is a Non-Dead Building Ghost a Building Zombie?

August 24, 2017

Another old picture, but this one is not quite a ghost. The curved mansard roof (that is visible as a curved pattern on the side wall) was part of the extent building before its unfortunate extension. The extension added one full story and made the mansard level the same size as the typical floors below, […]

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Building Ghosts From 15 Years Ago

August 23, 2017

I’ve been digitizing old rolls of film* and I came across a bunch of pictures I took, between 15 and 20 years ago, of building ghosts. Most of these ghosts are no longer visible: the current building boom in the city has resulted in the disappearance of a lot of vacant lots and parking lots, […]

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Beautiful Brickwork Marred

July 25, 2017

Friend of OSE – and occasional collaborator – Glenn Boornazian sent me a few vacation photos from Massachusetts. That’s pretty nice masonry for an apparently abandoned building. In a non-aesthetic sense, the interesting stuff is going on near the eaves. That’s a damned big crack and displacement at the corner pier. The crack starts at […]

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A Square Peg In A Square Hole

July 20, 2017

If you wait long enough, every aspect of a given technology will change. Square reinforcing bars used to be fairly common in concrete, but they’re long gone in design practice. Plain reinforcing bars, without surface deformations, used to be fairly common in concrete, but they’re long gone in design practice. Of course, just because we […]

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Tragedy in Context

July 6, 2017

A fire engine on its way to the Triangle Fire, 1911: I’ve been reluctant to discuss the fire at the Grenfell Tower in London, largely because I didn’t see that I had anything original to say about it. I’m only slightly familiar with codes and practice in the UK and this horrific tragedy doesn’t lend […]

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