Figure 7. Blocks (heavy lead-lined).
(1) Sheet-lead strips are laid under lead-lined partitions and project inside the exposure room to provide a
minimum of 1-1/2-inch lap with the floor sheet lead. Sheet lead up to 3.0 millimeters thick placed on the floor will have a 1-
1/2-inch lap with adjacent sheets. Floor sheet lead over 3.0 millimeters thick is applied in two or more layers 3.0
millimeters or less in thickness with 1-1/2-inch minimum lap at all joints, or in a single layer with all joints butted and
covered with a 3-inch lead strip not less than the thickness of the floor sheet lead. See figure 8 for details.
(2) Where lead-lined thresholds are not required, the lead strip under the partitions previously described herein,
is continued at the door sill opening. The strip shall be at least 12 inches wider than each door jamb opening and
extended 12 inches beyond the door jamb opening. See figure 9 for details.
(3) When the floor slabs above the exposure room are scheduled to receive sheet lead, the entire area so
designed must be covered with sheet lead, in the same manner previously described herein for floor lead. Sheet lead
shall extend to a minimum of 12 inches beyond the centerline of the lead-lined partitions located in the room below.