300 mm 12 inches.] Cement side and end laps together with solid mopping
of asphalt or heavy coat of asphalt roof cement. Nail side laps at 150 mm
6 inch intervals. Apply asphalt mopping at rate of 10 to 18 kgs per 10
square meters 20 to 35 lbs per 100 square feet. Install two rows of nails
approximately 275 mm 11 inches apart down longitudinal center of each
sheet, with nails staggered at 450 mm 18 inches O.C.
][3.2.4
Vapor Retarder on Steel Decks
Solidly mop the mechanically secured insulation surface with asphalt before
installing vapor retarder. For a 2 ply vapor retarder, install each sheet
lapping 480 mm 19 inches over the preceding sheet. Lap ends not less than
100 mm 4 inches. Stagger the laps a minimum of 300 mm 12 inches. Cement
felts together with solid mopping of asphalt. Apply asphalt moppings at
rate of 10 to 18 kgs per 10 square meters 20 to 35 lbs per 100 square feet.
[For a vapor retarder consisting of one layer of asphalt base sheet, lap
each sheet 100 mm 4 inchesover preceding sheet. Lap ends not less than 100
mm 4 inches, and stagger laps a minimum of 300 mm 12 inches. Cement base
sheets together with solid mopping of asphalt.]
]3.2.5
Over Gypsum Insulating Concrete or Lightweight Insulating Concrete
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NOTE: Some types of light weight insulating concrete
may require bottom side deck venting; edit this
paragraph accordingly if bottom side-venting is
used.
**************************************************************************
One ply of venting inorganic base sheet shall be laid, without mopping, at
right angle to the slope with 100 mm 4 inch side laps and 150 mm 6 inch end
laps. Laps shall be bonded with hot asphalt. End laps shall be staggered.
Base sheet shall be [nailed 220 mm 9 inches on centers at side laps and in
2 rows 270 mm 11 inches apart down the center of the sheet with nails 450
mm 18 inches on centers and staggered] [attached to the concrete as
determined by uplift requirements]. The 2-ply vapor retarder shall then be
applied over the base sheet as specified above.
3.2.6
Over Concrete Decks and First Layer of Insulation on Steel Decks
The 2-ply vapor retarder shall be applied as specified above except that
venting inorganic base sheet shall be deleted.
3.2.7
Over Structural Concrete on Non-Venting Support
One ply of venting inorganic base sheet with mopping holes shall be laid
dry at right angle to the slope with 100 mm 4 inch side laps and 150 mm 6
inch end laps. The vapor retarder shall then be applied as specified.
[3.3
INSTALLATION OF VENTILATING FELT
**************************************************************************
NOTE: Specify ventilating felt for new and existing
concrete decks suspected of having retained moisture
to aid in dissipation of any moisture retained in
concrete. This felt shall not be considered to be a
vapor retarder.
SECTION 07220
Page 22
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