Modified bitumen consists of a base sheet and a top cap sheet. The two pieces create a thick waterproof membrane that is very rugged.
Fully Adhered Modified bitumen works well for smaller areas with a very subtle slope. It comes in rolls that are 3’ wide, therefore it will typically have more seams than EPDM which is why it is suited for areas that are smaller with a tiny bit of slope. It is composed of two parts: The base sheet, which is applied first and adhered to the decking, and then the cap sheet.
Welded (Torch Down) Mod Bit is used in commercial applications and torched down to the base sheet at the seams to provide extra adhesion.