FIREPROOFING IN CONGESTED DISTRICTS. 119 
under pressure, and therefore can not be repaired with fire hose, as 
suggested for water mains. There seemed to be some fear in San 
Francisco that the breaking of the sewers and the water mains would 
cause the water to be contaminated by the sewage; but evidently if 
means were devised to maintain a good pressure in the water pipes 
this pressure in itself would protect a leaky main from such con- 
tamination. 
FIRE-RESISTING FEATURES OF BUILDINGS IN "CONGESTED 
DISTRICTS." 
FIREPROOFING. 
The Baltimore and San Francisco fires, as well as many other 
fires and fire tests, have proved conclusively that commercial meth- 
ods of fireproofing are inadequate to stand any severe test. In most 
buildings the steel work is fairly well protected, but the number of 
failures is sufficiently great to show that the factor of safety against 
fire is not by any means what it should be. 
For the protective covering itself to suffer complete destruction, 
or almost complete destruction, in any one fire is in itself a failure, 
because under such circumstances the steel work is very near destruc- 
tion and the margin of safety is altogether too small. It is more 
than probable — almost certain, in fact — that a detailed investigation 
of all the buildings in San Francisco would reveal many " protected " 
columns, not indicated in this report, that buckled as a result of the 
failure of the covering. In my judgment, columns should either be 
covered with 4 inches of brickwork, laid in Portland-cement mortar, 
and have all of the interior space filled with concrete, or else they 
should be inclosed in an expanded-metal jacket and the entire inte- 
rior filled with concrete, so that the minimum thickness of the con- 
crete would not be less than 4 inches. Exposed flanges of girders and 
beams should be protected by the equivalent of 1| to 2J inches of 
solid porous terra cotta, according to circumstances. If concrete is 
to be used, this thickness should be increased by about half an inch. 
The protection for lower flanges should always be inclosed in a basket 
of expanded metal or heavy wire lath, securely anchored into the 
side protection of the webs. The San Francisco experience showed 
that, even in a hot fire, such metal-mesh basket work will largely 
retain its tensile strength, and thus hold in position the fireproof cov- 
ering inside even though the latter should be shattered by expansion 
stresses or otherwise. The webs of the girders should be covered by 
4 inches of brickwork or concrete, built up on the lower flanges. 
Girders should be completely covered from bottom to top before the 
floor systems are put in. so that the collapse of the latter will not 
expose the girder. Floor beams should have heavy, solid protecting 
