The Untouchables

Some years ago, I ran a series of posts about incompatibility. What they pretty much all had in common is that two of the simplified models of buildings that we use in design conflicted with one another, so you were forced to choose which one would govern in any given situation. Today’s photo shows a similar type of problem, when the standard practice of the past comes up against the standard practice of today and they differ:

You are looking at the juncture where two buildings meet. The taller wall that is sharply angled away from us on the left is a fairly new building, constructed within the last ten years. The wall with the tan terra-cotta parapet caps was built in the 1920s. If you look closely it’s actually fairly easy to see a number of differences between the two walls despite their similar color.

The new wall follows the plane of the lot line extended up into the air. The old building has a courtyard between where I was standing and the portion that you see here: it’s a U shaped building and I was on the roof of one leg looking across at the other leg. The old building was constructed full to the lot line, because (a) the idea of seismic gap was not yet in place (I think) in the 1920s and (b) even if it had been, New York didn’t require seismic design until the 1990s. The new building was built with a code requirement for a seismic gap, which didn’t matter at the courtyard, but caused a problem at the ends of the U wings on the old building. If you look very closely, the end of the old building is almost perfectly in line with the plane of the brick veneer on the new building. By omitting the veneer where the buildings actually abut, the designers of the new building got a seismic gap of probably around 6 inches (the thickness of the brick veneer plus whatever cavity thickness they have between the veneer and the back-up). It looks like the old building is slotted into the new but it’s not: they’re both going right up to the lot line plane without crossing it, except for the new building being set back where they would meet by virtue of omitting the veneer there.

Note that I already used my favorite idea for today’s title on a blog post about a roughly similar condition: I’m Not Touching You I’m Not Touching You.