what is j channel used for
Products custom made to order. J Channels are designed to be used in metal roofing applications. The J channel flashing metal acts as a receiver for metal roof panels, ridge caps and headwall flashing. It also helps waterproofing a roof, since its installation is water directional.
'J' channels are even improperly used on Fiber Cement Siding! Note: The actual examples below are not indicative of every siding job with 'J' Channels. All photos below are from the same area on the same wall of one house. This is the northeast side of a home located about 2 blocks from the NJ shore.
The Solution. When vinyl J channel is used at the bottom like this proper flashing is essential especially at the corners. Also; 1/4 inch weep holes should be drilled about 12 inches apart into the J channel only. This will help keep the track dry and prevent accumulation of unwanted moisture.