B.U.R. Membrane Application Over Urethane/Isocyanurate Insulation Products

32 – April 1986

The Roofing Insulation Committee of the Thermal Insulation Manufacturers Association (RIC/TIMA) U.S. have, during the last few years, conducted research as to why some roof membranes in a built-up roof system had a tendency to blister when applied directly over polyurethane/polyisocyanurate.

Insulation Panels

Following extensive field and laboratory evaluation, jointly conducted in the U.S. by the NRCA and RIC/TIMA, it was agreed that in an attempt to minimize the potential for blistering between the top facer of the polyurethane/polyisocyanurate insulation and the roof membrane, the following application procedure was recommended:

“Over the top surface of the polyurethane/polyisocyanurate insulation apply a thin layer of fibreboard, or perlite board or glass fibre insulation, staggering the joints from the layer below.  Apply the roof membrane as specified.”

This procedure applies also when using composite board of polyurethane/polyisocyanurate insulation.