Consider the following
a) Polyurethane foam resins field-sprayed to uniform
thickness (1 inch (25 millimeters) minimum thickness, 2-1/4
inches (57 millimeters) maximum thickness) (two to three inches
(51 to 76 millimeters) in semi-tropical environments) for best
control of foam cell size, density, and overall uniform foam
b) Membrane coatings applied to sprayed polyurethane
foam substrates should always be fluid-applied. Fluid
application works best with sprayed polyurethane foam because it
fills the irregular substrate and adapts better to the slightly
irregular surface of sprayed foam, to the "day's-work"
termination details, and to the flashing of sprayed foam
substrate. Foam applied today must be coated today. Coating
should be applied in two or more coats with total minimum
thickness as follows: 30 mils (0.76 millimeter) for silicone, 40
mils (one millimeter) for urethane or acrylic. In hot climates
increase urethane to 45 mils (1.1 millimeter) and do not use
Flashings. Fluid-applied flashings are generally self-
sealing extensions of the membrane coating, applied
simultaneously. Always specify cants.
Applicable Details. Polyurethane Foam Contractors'
Division of the Society of Plastics Industry and Manufacturers'