A foam roofing underlayment is provided with a reinforcement membrane having an array of fastener elements for engaging fastener elements on a flexible roof membrane. The underlayment is formed by molding foam between the reinforcement membrane and a carrier membrane. The underlayment in secured to the roof using washers having fastener elements for engaging the fastener elements of the flexible roof membrane. An anti-peel flap with fastener elements is provided around the periphery of the washers. A slip sheet is used between the underlayment and the flexible roof membrane to permit accurate positioning of the flexible roof membrane prior to engagement of the fastener elements. The interstices between the fastener elements provide lateral moisture paths to vents in the flexible roof membrane.

A method is disclosed for dispensing a polyurethane mixture onto a substrate by generating a liquid mixture from reactive component resins; introducing the mixture in an inlet section of a dispensing device so as to advance it towards a planar-shaped outlet slit section, transversely to the advancement direction of the substrate; distributing the mixture along a gap chamber having a cross section diverging towards the outlet slit section; and dispensing the mixture through the outlet slit section, so as to deposit a thin, uniform film onto the substrate. Fractions of the mixture travel equal distances from the inlet section to the outlet slit section, in equal times, maintaining equal average speeds along each section having zones placed all at the same path distance either from the inlet section or from the outlet slit section.