Count on IKO for the best in built-up roofing systems. IKO Built-Up Roofing (BUR) Systems are composed of layers of roofing asphalt and asphalt felts which are installed so that the multiple interwoven plies form a roofing membrane. The key to this system is the repetitive layers. IKO Type IV and Type 6 Glass Ply Sheets and No. 15 Perforated Felt–Imperial stand out as durable built-up roofing membranes that contractors can rely on.