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Telegraphing Through

by Don Friedman on October 20, 2017


Another artistic photo, this time of one face of a party wall in a rowhouse. If you look closely (click on the picture to expand it), you’ll see that the plaster is well-adhered to the brick. The plaster didn’t fall off in that one area, it was removed. Why? Because the presence of that long, ugly, and new crack in the plaster suggested that there was damage in the brick wall behind, and the only way to be certain was to remove some of the plaster. If you look closely again you can see the crack quite clearly in the brick wall, although it goes through the mortar joints, not the bricks themselves.

A large part of building investigation is inferring conditions from limited information. Plaster is useful in that it is often attached to wood-joist floors, wood-stud partitions, and brick walls in a fairly rigid manner that forces it to move with the underlying structure. Plaster is both brittle and quite weak, so when it’s forced to move it cracks. The is usually referred to as “telegraphing” in that we don’t see the actual movement, we just get a message. And, just like real telegraph messages back in the day, the news is often bad.

Different Types of Efficiency

October 19, 2017

I seem to keep coming back to train station roofs as I write. That’s happening partly because I travel by train a good amount so I’m looking at those roofs, and partly because they tend to have exposed structure designed by engineers with little or no separate architectural design, which may not make them beautiful […]

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This Is Ungood

October 18, 2017

From a few years ago, some rotting wood beams and a failing brick pier. In 1989, I performed a long and difficult site visit to check on a structure I won’t name (confidentiality is still in place, even after all these years) that had to be reviewed once per year. The fellow who had been […]

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Detailing For The Forces

October 17, 2017

A big part of structural design is “detailing,” which is drawing the way various pieces of a building  are connected. The bridge above (click to enlarge all of the photos) is in Wrocław and has a shorter span than the average American suspension bridge of any era. I walked over it a number of times […]

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Road Trip: An Orphaned Wall

October 16, 2017

Seen on the street in Ottawa… I’ve mentioned orphans walls once before. They are what’s left when old walls are incorporated into new buildings in a manner that makes it difficult or impossible to demolish the wall when the original building is demolished. In this case, the light-red wall with white trim obviously belonged to […]

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Road Trip: Hanging

October 15, 2017

That’s a picture of three men on bosun’s chairs cleaning a glass curtain wall in central Ottawa. Bosun’s chairs have fallen out of favor in New York, so I don’t get to see this very often. A fifteen-story or so building like this back home would have either tracks for a scaffold built into the […]

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Road Trip: For Show Or For Blow

October 14, 2017

(Ignore the flying porpoises. I have no idea what they are.) That’s the roof of a shopping mall in Ottawa. Are those trusses real structure or just for show? Their form (diagonals sloped for tension, deepest at midspan) and location (paired on either side of the columns) both make sense as real structure. If so, […]

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Flavors of Obsolescence

October 13, 2017

This article in Curbed gets the facts right but also, by accident, emphasizes a point of unclarity that has led to a lot of sensational headlines over the years. There are some 2000 bridges of various types in New York City, most of them small. It sounds horrifying that 76 percent are “functionally obsolete” and […]

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Road Trip: Adaptive Reuse Hotel

October 12, 2017

I’m currently at the APT conference in Ottawa, and that’s my hotel, the Metcalfe, above. It was built circa 1906 as a YMCA and has been converted to a nice boutique hotel. You can always repurpose a building if you want to.

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A Concrete Building

October 11, 2017

A market hall in Wrocław, Poland: That’s how you do exposed concrete. The hall has the basic layout of a church, with a cross plan for the high gable roof and lower infill between the cross arms. The roof and its clerestory are supported by a series of parabolic concrete arches, which intersect at the […]

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