There are numerous variations of modified membrane roofing materials but primarily they are a thick multi-plied granulated capping sheet. They came on the market to be used as the dominant roofing membrane over a base sheet on flat roofs. A base sheet and a modified cap sheet are equal to the 3-ply BUR roofs discussed earlier.
Additional uses were quickly discovered for the modified membranes because of their flexibility and their durability. Their elasticity allows them to be used for various expansion details on many flat roofs or any other type of roof. Membranes like these, that should be able to weather sun and rain exposures, can be used as flashing materials. When they are covered by the primary roofing materials, they provide for a durable long life expectancy.
These membranes can be used as valley material, open cricket material and any other locations on the roof that become water soaked. They will even make an excellent underlayment membrane due to their self-sealing characteristics around penetrations and elasticity. The majority of better underlayments use rubberized modified combinations in their matting make-up with or without the granulated surface. The thicker the underlayment, the more durable and damage resistant it will be. This will provide for a better waterproofing agent thereby giving your roof a longer life.
The modified membranes can be attached by the use of hot asphalt or cold asphalt adhesives. They can be torched down and melted to the surface they are covering. You should be aware that insurance companies hate this method due to the fire danger. This includes the roofer's own insurance carrier. These membranes can also be attached by a self-adhering backing found on the more expensive modified materials.
Modified membranes provide for better roofing ply material regardless of the type of roof or the type of application. They have been proven to outlast any other type of ply-sheeting no matter what the environment.