Section 27-646. Thickness of glass

Thicknesses of glass panels shall be
  chosen either on the basis of  statistical  probability  of  breakage  (
  subdivision  (a)  of this section) or on the basis of table 10-7, at the
  designer's option.
    (a) Statistical probability. Thickness of glass panels shall be chosen
  so that the statistical  probability  of  breakage  when  the  glass  is
  initially  subjected to the design wind load specified in table RS 9-5-1
  does not exceed the values indicated in table 10-6. Probability or  load
  factors  used  for  design shall be derived by test. The sufficiency and
  validity of  such  test  data  shall  be  subject  to  approval  by  the
  commissioner.
    (b)   Alternate  requirements.  Alternative  to  the  requirements  of
  paragraph (a) above, the thickness of glass panels may  be  chosen  from
  table  10-7.    For  glass  with  assured minimum thickness greater than
  required by reference standard RS 10-68, the maximum areas in table 10-7
  may be increased in proportion to the assured minimum thickness.
 
            TABLE 10-6  Probability of Breakage for Glass Panels
                 (Based on Coefficient of Variation of 25%)
  ========================================================================
     Elevation Above Grade
     of Mid-Point of Glass                Area of Panel--Sq. Ft.
  ------------------------------------------------------------------------
  -Ft......................   0-60      60-80     80-100   100-120   120+
  0-50.....................   1.0%      1.0%      1.0%     1.0%      1.0%
  50 or more...............   1.0%      0.8%      0.6%     0.4%      0.2%
  ========================================================================
 
                 TABLE 10-7  Maximum Area of Glass--Sq. Ft.
  ========================================================================
                                        Elevation Above Grade of Mid-
                                            Point of Glass--Ft.
  Nominal Thickness
  of Glass--Inches                   0-50      50-300    300-600     600+
  ------------------------------------------------------------------------
  Sheet Glass
    Single strength.............       9         9           8         7
    Double strength.............      13        13          11        10
     3/16"......................      25        25          21        19
     7/32"......................      32        32          27        24
  Plate and Float Glass
     13/64".....................      25        25          21        19
     1/4".......................      37        37          32        28
     5/16"......................      54        54          46        40
     3/8".......................      78        74          63        58
     1/2".......................     114       100          86        75
     5/8".......................     152       120         103        90
     3/4".......................     210       137         118       103
     7/8".......................     241       158         135       118
     1".........................     312       204         175       153
  ========================================================================