An Oxymoron

The 1889 Schermerhorn Building at Lafayette and Great Jones Streets:

This commercial loft building is, unsurprisingly, a designated landmark and has been 1966, at the very beginning of landmarking in New York. The most noticeable architectural feature – I was going to write “most unique” but, whew, side-stepped that trap – are the ground-floor stone columns. The designation report describes this feature: “The piers, supported at the first floor by interesting dwarf columns of sandstone, rest on polished gray granite bases.” I can’t find a specific reference for “dwarf columns” other than the architecture of role-playing fantasy games, but those columns are far from ordinary. From the top of the base to the bottom of the capital, the columns are maybe twice as high as they are wide, compared to the six to one ratio of the stockiest of the classical orders. To me, it feels like the weight of the building above has squashed the columns.

What’s funny about this is that the facades are actually quite open for a bearing-wall building. The masonry openings for the windows are wide, with the metal (I think) mullions and spandrel panels inset. In other words, at the first through fourth floors, the wall has been reduced to the piers and curtain-wall like panels at the windows. That raises the question of why the wall feels so heavy and the answer, to me, is the out-of-plane thickness of the wall. Look at the first or second floor windows and you can see the solid thickness of the piers.

Time to go to the source: at the time this building was constructed, the wall geometry was largely prescribed by the NYC building code. For a non-residential building 75 to 85 feet in height, the walls had to be 24 inches thick “to the height of twenty feet, or to the nearest
tier of beams to that height”, then 20 inches thick to 60 feet, then 16 inches to the top. But the walls are visibly thicker than two feet, so what’s going on? First, “If any horizontal section through any part of any bearing wall in any building shows more than twenty-five per centum area of flues and openings, the said wall shall be increased four inches in thickness for every ten per centum, or fraction thereof, of flue or opening area in excess of twenty-five per centum.” Nice clear language, but simply put, if more then 25 percent of the length of the wall is open, the wall has to get thicker. That is definitely true at the lower floors here.

Second, “In all walls the same amount of materials may be used in piers or buttresses.” In other words, if your wall is 20 feet long and the code thickness is 2 feet, your wall is 40 square feet in plan. You can substitute three piers, each 3 feet 4 inches wide, which gives a pier length of ten feet, so the piers would have to be 4 feet thick to give the required wall area.

TL;DR: prescriptive wall geometry works, but it tends towards the over-conservative.