142 THE SAN FRANCISCO EARTHQUAKE AND EIRE. 
were closely built in long rows extending over entire blocks. In the 
business district almost every separate structure was close to its 
neighbors. Wide, uncovered spaces separating buildings were, as a 
rule, confined to the outlying suburbs. In the compactly built dis- 
trict of wooden structures a house every three minutes was fre- 
quently the rate of destruction from the fire during the high wind 
that prevailed at times. 
In the congested business district about 75 per cent of the streets 
were 60 feet wide, and a few (about 30 per cent) were at least 80 
feet wide. These streets offered very little obstruction to the passage 
of the flames or heated air, and it was aided by the winds that were 
caused largely by the conflagration. 
The height limit as established by the city ordinances was 220 feet 
for buildings of class A, 100 feet for class B, 82 feet for class C, 
and 45 feet for frame buildings. Brick buildings with wooden joists 
were therefore allowed to be built to a height of eight stories if 
furnished with wire-lath and plaster ceilings, thus affording the fire 
admirable opportunities for destruction. 
BEHAVIOR OF STRUCTURAL STEEL AND STEEL-FRAME 
BUILDINGS SUBJECTED TO THE EARTHQUAKE AND 
FIRE. 
EFFECTS DUE PRIMARILY TO THE EARTHQUAKE. 
INTRODUCTION. 
Structural steel as a building material and as a principal stress 
resistant in high steel-frame buildings has greatly increased in favor 
since its entirely satisfactory behavior in the recent great vibrations 
in California ; for while it possessed strength and stiffness to a satis- 
factory degree, it also displayed an amount of elasticity that avoided 
much shearing and fracture, even under the vibrations of the tallest 
steel- frame structures. 
The behavior of structures of the various types in San Francisco 
and elsewhere in the area destructively affected by the earthquake 
was in strict accordance with the merits of their foundations, design, 
materials, and workmanship. The so-called fireproof buildings 
within the area most affected by the earthquake, and afterwards, in 
San Francisco, burned over, did not exceed 60 in number. Among 
these buildings were 8 having steel frames and hollow-tile floor 
arches, 29 or 30 having steel frames with reenforced-concrete floor 
arches, and 2 having reenforced-concrete frames — one of these of 
imperfect design. There were 6 unfinished buildings with steel 
frames, and 10 having brick walls and fireproof floor arches. 
