Roof Surface Preparation
RUBBERALL® roof membrane will adhere to certain isocyanurate insulation boards compatible with RUBBERALL® adhesives. Solvent based adhesive will melt the polystyrene. Water based adhesive will not adhere to polystyrene. The roof membrane will also adhere to plywood, OSB (Oriented Strand Board), and one-half inch (1/2") high-density wood fiberboard and concrete. Polystyrene insulation may not be adhered directly to rubber membrane. If polystyrene insulation is used, cover insulation with one-half inch (1/2") high-density wood fiberboard. Butt all insulation boards together, staggering all of the joints. All spaces larger than one-quarter of an inch must be filled to provide a uniform, smooth surface.
Screws and deck plates shall be applied at the minimum rate of eight (8) per 4 ft. x 8 ft. sheet of insulation, and five (5) per 4 ft. x 4 ft. sheet or as required by the insulation manufacturer. When installing insulation around the perimeter, the fastening pattern is one (1) screw and one (1) deck plate every two (2) square feet (that is sixteen fasteners per 4 ft. x 8 ft. sheet). Examples of fastening patterns are shown in Figure 1. NOTE: Extra fasteners should be installed around protrusions such as pipes, chimneys, skylights and irregularities in the roof deck.
Figure 1 — Fastening Pattern
Do not install more insulation than can be covered with RUBBERALL® membrane by the end of the day.
Reroofing over a wet substrate is not good roofing practice. All wet material should be removed and replaced.
The roof surface must be dry. Moisture will cause poor membrane adhesion and blistering.
The roof surface should be swept to remove dirt, dust and other loose particles.
Good roofing practice dictates that the roof surface must have positive drainage of at least 1/8 inch in 12 inches.