Historic Structural Detail 3, Sort Of

by Don Friedman on August 22, 2011

Construction projects are full of changes and this was just as true in the past as it is now. In particular, where different trades’ and/or different designers’ work meets, there is a good chance that the as-built condition to not look like the drawings.

Recently we’ve been looking at cornice supports at the building where we previously found some interesting cast-iron details. Most tall metal-frame buildings that were constructed between 1900 and 1930 use outriggers (short, closely spaced cantilevered beams – most often double angles) to support cornices, with some kind of hanger rods below the outriggers to support the cornice soffits. This design creates an interesting condition at the corners, where the square masonry block that makes up the corner of the cornice is supported on two adjacent sides, as opposed to all of the other blocks, which are supported on two opposite sides. The corner blocks are less secure and have an unsettling tendency to be unsettled: they want to rotate outward away from the building.

At our current project, it’s clear that someone (the iron designer, probably) wanted to install an extra outrigger running from the corner of the main facade out to the corner of the cornice. At one corner there are holes for fasteners that were never installed; at another there is the top connection for the non-existant diagonal outrigger:
The east outrigger is on the left, the north outrigger is on the right, and the connection for the diagonal is between.

My guess is that the mason said “Exactly how do you expect me to install the corner block with that diagonal in the way?” and the diagonals disappeared from the job.

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