148 THE SAN FKANCTSCO EARTHQUAKE AND FIRE. 
The weight of Portland-cement concrete is a drawback, and, 
moreover, concrete is expensive when well made and applied. Cinder 
concrete was well esteemed for fireproofing for floors, but the scarcity 
of good cinders in the city rendered its general employment imprac- 
ticable. 
TERRA COTTA. 
As fireproofing for floors terra-cotta tiling has not given universal 
satisfaction. It is lighter than concrete, but the wrenching of build- 
ings during the earthquake opened many of the joints and the mor- 
tar was destroyed — as in the Mills Building, a large ten-story steel- 
frame structure of the older type, having self-supporting walls. The 
mortar joints in the tiling were started by the earthquake, and the 
mortar was disintegrated by the fire, the floors being destroyed and 
the lower surfaces of the tiling badly spalled. The same effect was 
noticeable to a certain extent in the excellent Union Trust, Crocker, 
and James Flood buildings. In the last named the flooring was fire- 
proofed with terra- cotta arched tiles, covered with concrete on top 
and finished beneath by an efficient ceiling' plastered on wire lath. 
The fireproofing was less injured in this building than in almost 
any other. 
Terra-cotta fireproofing of columns was in many buildings a fail- 
ure, not so much on account of the nature of the material as because 
of its insufficiency in quantity and poor or imperfect method of appli- 
cation. Wooden studs were in many places put behind the terra 
cotta. These burned out quickly, leaving the material unsupported. 
Pipes and wires were run up between the column and the fireproof- 
ing, and the twisting or expansion of the pipes caused by the earth- 
quake movement broke the protecting cover. Imperfect junctions 
with ceilings above or floors beneath were common. That such imper- 
fect construction should never be adopted has been fully demonstrated 
in San Francisco. 
Porous terra cotta has been found more satisfactory than the hard 
and glazed varieties. For inclosing columns, the round porous forms 
have proved more stable and efficient than the rectangular ones, as 
shown in the Spring Valley Water Company's building (PI. XLV, 
A) and the Aronson Building (PL XXVII, B). 
PLASTER AND METAL WORK. 
Common plaster on wire mesh, metal lath, or expanded metal was 
very generally used for the fireproofing of columns, partitions, and 
the like, on account of its cheapness, but was a failure when subjected 
to a hot fire, as proved in the Hotel Fairmount (PL XXXIV), the 
Hotel Hamilton, and several other buildings. This failure was much 
more noticeable where only a single wrapping or thickness of the wire 
