When your roof begins to leak, one of the first things you should consider to stop the leak is a chimney flashing repair. Over a period of time these flashings or the sealant can deteriorate and begin to leak. To correct this problem you'll need to find the leak and repair it.
Step 1 – Remove Leaking Shingle Sealant
The surest way to stop a flashing leak will be to replace a bad flashing or replace the sealant around it. If your flashing is still in good condition, remove the sealant and replace it. Lift the shingle edges enough to get at the sealant and cut and scrape it away, using a utility knife to cut and a putty knife or paint scraper to remove old sealant. Clean off any dirt or debris from the surfaces near the flashing edge where it meets the shingle or chimney surface
Step 2 – Re-Apply New Caulk
.Using your caulk gun to apply new polyurethane caulk along the edges of the cap flashing where it meets the mortar of the chimney. Apply a bead of caulk along the exposed bottom edges of the shingle flashing.