The Type IV Glass Ply Felt is manufactured from a heavyweight fiberglass mat containing heat-cured resinous binders for added dimensional stability. The high strength glass mat is saturated with type IV asphalt, which provides excellent breaking strength and uniform porosity for improved ease of application. It may be used as an inner ply or base ply in Carlisle multi-ply systems. It may be used as a base ply when mopped in place over asphalt-compatible substrates. When installed in a two ply format Carlisle's Type IV Glass Ply Felt may be used as a temporary roof. It can be used as a vapor retarder.