0092 Blisters in Built up Roofing Membranes - Flat Roofing - Built up Roofing -

Image Text: Cross section > gravel is driven off the rising blister exposing it to ultraviolet or mechanical damage > trapped air/water > gravel > roof sheathing > blister caused by air or water trapped between the ply's of the membrane (or between the sheathing and the membrane) > 4 ply membrane > crater left over from broken blueberry blister permits water penetration that can weaken the roof > gravel > blueberry blister due to air/water trapped in the asphalt > 4 ply membrane > roof sheathing