Straight line chimney flashing. New and Improved! ...  Or is it?

Counter flashing a chimney above the roofline has traditionaly been done by cutting or chiseling the mortar from between the masonry bricks and inserting metal flashing to cover the sub or shingle flashing. Many roofing contractors are now using diamond tipped saws to cut through the bricks on a chimney instead of cutting out the mortar in the joint to install their counter flashing. There are a few instances where this new method is acceptable. Such as on new construction where the masonry is hard fired bricks and joined with mortar containing a high amount of Portland cement. It is not acceptable on old soft masonry bricks and historical buildings.

Below is a photo of a slate roof and chimney on a house built approximately 80 years ago. The original roofers, or maybe it was the masons, installed the chimney counter flashing as a straight metal flashing following the roof line. This was done because the uneveness of the stone used makes it hard to install a metal flashing that conforms to the stone and gives a smooth appearance. The stone was chiseled flat from the roofline about 4 inches up the side of the chimney. Then a groove, or reglet, was cut into the stone about an inch deep with a stone chisel to accept the counter flashing.

The replacement flashing was installed in the same way.  The previous flashing, poorly installed and sealed with caulking, was removed (and as much of the tar as economically feasable) and the joint cleaned. New flashing fabricated, installed, and secured with lead fasteners. Then new mortar mixed to closely match that of the original was pointed into the joint for a permanent seal.