Historic Structural Detail: Heavy Metal

by Don Friedman on March 28, 2016

This:

IMG_1307

is a box girder consisting of two I-beams and two plates, all riveted together. It’s at the next-to-top floor of an old mansion, where there is a small terrace at the front because the top floor is set back several feet. The girder is below the set-back facade; the steel beams supporting brick vaults are the roof of the terrace. It’s not clear why the brick vaults were used for this roof, since the main roof has wood joists, the same as the interior floor.

This girder, which is the heaviest structural element in the building, is a nice example of the designer fitting the structure to the requirements. The floor can be supported by wood joists, so it is. The set-back wall requires a heavy girder, so it has one.

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