Proper chimney flashing is actually three layers working together: step flashing tucked under each course of shingles, counter flashing set into the mortar joints of the chimney, and on the high side of the chimney, a properly built saddle (or 'cricket') to divert water around it instead of trapping it. When any one of those layers is missing or improvised with caulk, water finds its way in.
We rebuild chimney flashings the way they should have been built originally — with new step and counter flashing, fresh ice-and-water shield, and a real saddle on chimneys wide enough to need one. The result is a connection that should outlast the chimney itself.
If your chimney is leaking, don't let anyone solve it with a tube of sealant. Sealant fails. Flashing, done right, doesn't.
