Dead Valleys are roof areas where one eave joins directly parallel to another roof eave. Such a situation creates a very flat area where water and debris from both roof planes will gather.
Dead valleys are called a “roofer’s nightmare” because they can be very tricky. When a metal roof is installed, the property owners are expecting an end to all of their roofing troubles. This includes the dead valley areas so they must be addressed very carefully.
Whenever possible, look for options to put as great of a pitch as possible on the dead valley, either by raising it at one end or in the middle. By doing this and then using a standard Open Valley system, a permanent solution can be found. In other cases, however, a large metal pan valley can be fabricated and installed in these areas. The dead valley area should be opened up as far as possible, starting the roofing installation well up on the pitched roof areas. Keep in mind that, particularly in heavy rains, water might wash upward from one side of the roof onto the other side. Care must be taken to ensure that water and debris from the adjoining roof planes cannot become blocked or trapped and instead has a clear path of exit from the roof. Consult the roofing manufacturer as necessary, obtain wide metal for fabrication of this pan, and ensure that dissimilar metals do not contact one another. If the dead valley is to be installed with a non-metal product, refer to Technical Bulletin #37 on transitions to low pitch, non-metal, roofing.