Built-Up Roofing - Page 6

Built-Up Roofing Specifications

6.11.6 Fastener Spacing

For 3, 4 and 5-ply roofs, locate a nail at each nailer, spaced ¾ " (19 mm) from the leading edge of each felt, as it is installed.

Termination of a continuous cap sheet MUST occur at a nailer. At points of termination, place 5 nails across the 36" (914 mm) width of the endlap of the cap sheet and into the nailer. The first nail is to be spaced ¾ " (19 mm) from the leading edge of the cap sheet, with the remaining 4 nails spaced approximately 8 ½ " (216 mm) o.c., with the nails staggered across the width of the nailer to reduce the chance of the cap sheet tearing along the nail line.

Nailing Pattern and Nailer Spacing shown with 3-Ply System.

Nailing Pattern and Nailer Spacing shown with 4-Ply System.

Nailing Pattern and Nailer Spacing shown with Cap Sheet Roofs.

6.12 Phase Construction

6.12.1 One of the greatest hazards of roof construction is the application of a roofing system in "phases". Phasing is a construction sequence in which a partially completed roof system is left exposed to the weather, for a period of time, even overnight. The remainder of the roofing system is installed at a later time. This can lead to entrapped moisture which can cause premature failure of the membrane.

6.12.2 Good roofing practice dictates that no more roofing materials should be applied at any one time, than can be completed in one day. This means that the finished membrane MUST be installed all in the same day. Water cut-offs must be installed at all exposed edges of a day’s completed work and completely removed prior to commencing the next day’s work.

6.12.3 Aggregate surfacing may be postponed for up to six months over fiber glass asphalt roofs, provided valleys and low spots are glazed with 10-15 lbs./sq. (0.49-0.73 kg/m²) of the interply asphalt. The roof surface must be free of dirt, debris and moisture prior to the application of asphalt flood coat and aggregate surfacing to assure proper adhesion. Surfaces that are excessively dirty should first be washed and cleaned with water, allowed to dry thoroughly, and then primed with JM Concrete Primer.