Editing Singer Building (section)

==== Superstructure ====
[[Load-bearing wall]]s initially supported the original Singer Building at 149&nbsp;Broadway, while the Bourne Building annex at 85–89&nbsp;Liberty Street had an internal [[steel frame|steel skeleton]].<ref name="LC p. 355" /> The original Singer Building was altered between 1906 and 1908 to use a steel skeleton.<ref name="Semsch p. 32" /> The entire building used 850 steel columns.<ref>{{harvnb|Semsch|1908|ps=.|p=21}}</ref> The columns were generally constructed in two-story segments.<ref name="Semsch p. 32" /> One- to three-story-tall column segments were used on the basements, first floor, and 14th through 16th&nbsp;floors.<ref>{{harvnb|Engineering Record|1907|ps=.|p=599}}</ref> [[Rafter]]s supported the mansard roof of the base, excluding the tower.<ref name="ER p. 602">{{harvnb|Engineering Record|1907|ps=.|p=602}}</ref> Milliken Brothers Inc. was the structural steel supplier for the project.<ref name="HABS p. 88" /><ref name="Semsch p. 202" />
[[File:Singer typical tower floor plan.png|thumb|alt= A typical floor plan in the tower section|Typical floor plan in the tower section]]
The Singer Tower addition of 1906–1908 had a steel skeleton and weighed {{Convert|18365|ST|LT t|abbr=}}.<ref name="LC p. 358" /> The tower's columns were spaced {{Convert|12|ft||abbr=}} apart on their centers.<ref name="ABM p. 429" /> Because the three center bays on each side contained windows, only the corners used diagonal [[Cross bracing|bracing]] and, as such, were treated as square prisms.<ref name="ER p. 602" /><ref>{{harvnb|Landau|Condit|1996|ps=.|pp=358–359}}</ref> Inside, there was another structure for the central elevator shafts, which were connected to the corners of the tower via longitudinal beams.<ref name="nyt19070825" /><ref name="LC p. 359">{{harvnb|Landau|Condit|1996|ps=.|p=359}}</ref><ref>{{harvnb|Semsch|1908|ps=.|p=22}}</ref> A [[girder]] supported the columns at the tower's corners at the fourth floor, while 36&nbsp;columns rose from the basement into the tower.<ref name="Semsch p. 202" /><ref name="ER pp. 542–543">{{harvnb|Engineering Record|1907|ps=.|pp=542–543}}</ref> Four pillars were placed at each corner of the tower and six more pillars were placed in the elevator shafts.<ref name="nyt19070825" /><ref name="ER pp. 542–543" /> Each [[truss]] extended upward for two stories, causing the columns and braces to act as wind-resistant cantilevers.<ref name="nyt19070825" /><ref name="ER p. 602" /> The braces on the north and south contained 11 panels each while those on the east and west contained 10 panels.<ref name="nyt19070825" /> The four columns at the center of the tower supported its dome.<ref name="Semsch p. 202" /><ref name="ER p. 543">{{harvnb|Engineering Record|1907|ps=.|p=543}}</ref>

The superstructure was erected using two boom [[derrick]]s. One of them, with a capacity of {{Convert|40|ST|LT t}}, a {{convert|75|ft|adj=on}} mast, and a {{convert|65|ft|adj=on}} boom, lifted the steel beams from ground level to a 17th-story platform. The other was installed on the 17th&nbsp;floor and had a capacity of {{Convert|25|ST|LT t}}; this derrick erected the tower's steel.<ref>{{harvnb|Landau|Condit|1996|ps=.|p=442}}</ref><ref name="Semsch p. 28" /> Generally, it took less than five minutes to transfer the steel from ground level to the superstructure.<ref name="Semsch p. 28">{{harvnb|Semsch|1908|ps=.|p=28}}</ref> German steel was used in the Singer Tower's framing because of Flagg's belief that German workmanship was better than that of Americans.<ref name="LC p. 359" /><ref>{{cite magazine|date=June 22, 1911|title=Why Steel Is Imported|url=https://babel.hathitrust.org/cgi/pt?id=uc1.31822036002657&view=1up&seq=503|journal=[[Engineering News-Record]]|volume=65|pages=765|access-date=August 17, 2020|archive-date=February 28, 2022|archive-url=https://web.archive.org/web/20220228144020/https://babel.hathitrust.org/cgi/pt?id=uc1.31822036002657&view=1up&seq=503|url-status=live}}</ref> The tower's superstructure was intended to withstand wind pressure of {{Convert|30|psf||abbr=}},<ref name="ER p. 543" /><ref name="rer19070427" /><ref>{{harvnb|Architects' and Builders' Magazine|1908|ps=.|p=430}}</ref> even though the highest recorded wind pressure in the neighborhood was less than {{Convert|10|psf||abbr=}} at the time of the Singer Building's construction.<ref name="rer19070427">{{cite magazine|date=April 27, 1907|title=Anchorage of Singer Building Tower|url=https://rerecord.library.columbia.edu/pdf_files/ldpd_7031148_039_18.pdf|journal=The Real Estate Record: Real Estate Record and Builders' Guide|volume=79|pages=824|via=[[Columbia University|columbia.edu]]|number=2041|access-date=August 17, 2020|archive-date=November 28, 2020|archive-url=https://web.archive.org/web/20201128051102/https://rerecord.library.columbia.edu/pdf_files/ldpd_7031148_039_18.pdf|url-status=live}}</ref><ref name="Ripley p. 9460">{{harvnb|Ripley|1907|ps=.|p=9460}}</ref>

The internal structure also used {{Convert|4520|ST|LT t|abbr=}} of [[Portland cement]] and {{Convert|300000|ft2||abbr=}} of concrete subflooring.<ref name="Semsch pp. 44-45" /> The Singer Building's floors generally used terracotta flat arches {{Convert|10|in||abbr=}} deep, and many of the internal partitions also used terracotta blocks.<ref name="Semsch p. 36" />