What type of flashing is recommended for a chimney penetration on a roof?

Counter flashing is recommended for a chimney penetration on a roof because it serves a critical purpose in preventing water intrusion in the area where the chimney meets the roof. When properly installed, counter flashing is placed over the base flashing that is integrated into the chimney structure, effectively redirecting water away from the roof and chimney intersection. This design helps to ensure that water flows over the counter flashing and down the roof, rather than infiltrating into the intersection, which could lead to leaks and water damage.

Base flashing is also an important component, but it is typically installed at the base of the chimney where it intersects with the roofing membrane and works in conjunction with counter flashing. Fascia flashing primarily addresses the roof edge where it meets vertical surfaces, and drip edge flashing is designed to direct water off the roof eaves, thus neither of these are specifically suited for the unique requirements of a chimney penetration. Therefore, the proper use of counter flashing is essential for maintaining the integrity of the roof around chimney penetrations.