Polyurea roof coatings are made of two components: isocyanate and polyol. Using transfer pumps, your roofing contractor will perfectly proportion your foam roof coating at a one to one ratio for the two components. Then the components are mixed in a spray gun and applied to the roof deck.
The foam roof coating must be applied evenly so as to prevent ponding, which can deteriorate the elastomeric top coating and expose your foam to the elements. With proper installation, though, the risk of ponding is alleviated and the roofing system should function properly for years to come.