Guastavino  Floor  Construction — The  brick  walls  of  the
kiln  in  this  case  were  corbelled  out  6  ins.,  and  a  rectangular
horizontal  iron  frame  was  built  into  the  upper  portion  of  the


TESTS   OF  FIREPROOF  FLOORS.  73

kiln-walls  to  take  the  thrust  of  the  dome.  This  system  re-
quired no  intermediate  floor-beams.  The  dome  consisted  of
three  successive  courses  of  flat  fire-clay  tiles,  which  sprung
from  the  side  walls  with  a  rise  at  the  centre  of  10  per  cent,
of  the  greatest  span.  The  tiles  were  6  ins.  wide,  12  ins.  to
18  ins.  long,  and  f  in.  to  I  in.  in  thickness,  being  laid  in
cement-mortar.  The  construction  was  built  on  a  wooden
center.  Two  kinds  of  floor  surfacing  were  used.  In  one
half,,  brick  ribs  extended  over  the  dome,  supporting  a  double
course  of  horizontal  flat  tiles,  which  received  the  finished  floor.
In  the  other  half,  cinder-concrete  filling  was  used,  with  em-
bedded nailing  strips.  Portions  of  the  ceiling-soffit  were
plastered,  and  some  spaces  of  tile  were  left  exposed.
The  initial  loading  gave  a  centre  deflection  of  .017  in.
Duration  of  fire-test,  9.15  A.M.  to  3.18  P.M.  Maximum
temperature  2,525  degrees.  Maximum  deflection,  0.71  in.
Nearly  all  of  the  plaster  fell  early  in  the  fire-test,  but  before
the  application  of  water  no  cracks  had  developed  in  the  ceiling,
and  no  tiles  had  fallen.  During  the  water-test,  portions  of
the  lower  course  of  tile  fell  in  pieces,  due  to  the  sudden  con-
traction. One  I-beam,  supporting  a  corner  smoke-flue,  be-
came exposed.  It  was  noticed  that  the  centre  of  the  dome
rose  gradually  under  the  influence  of  the  applied  heat,  which
caused  the  expansion  of  the  masonry  in  the  dome  construc-
tion. The  greatest  elevation  was  0.71  in.
