Blistering of Hot Applied Bituminous Built-Up Roof Membranes Over Plastic Foam Insulations

B LISTEP,ING OF LIQUID applied coatings is not new. The Reader’s Digest Complete Do-it-yourselfManual describes paint blistering over wood as &dquo;the result of paint applied to a wood surface that is damp or wet. The presence of water prevents the paint from gripping the surface properly. The solution is to make sure any surface is thoroughly dry before you apply paint [1].&dquo; Hot applied bituminous built-up roof membranes most commonly comprise alternate layers of hot liquid bitumen and bitumen impregnated cellulose or glass fibre reinforced felts, typically with three to five layers of felt. Blisters are defined as enclosed raised spots or areas that contain gas or liquid that show at the surface of prepared or built-up roofing (see Figure 1) [2]. Blistering of hot applied bituminous built-up roofing membranes is a