Flashing a chimney on asphalt shingles involves installing metal pieces to direct water away from the junction between the chimney and roof, preventing leaks. This typically includes two types of flashing: counter flashing and step flashing. Step flashing consists of small, L-shaped pieces installed along each course of shingles against the chimney side, overlapping each other to create a watertight seal. Counter flashing is a wider metal sheet embedded into the chimney mortar joints, covering the top edge of the step flashing. It prevents water from seeping behind the step flashing. Over time, chimney flashing can fail due to weather exposure, causing leaks or water damage. Basic DIY checks involve visually inspecting the flashing for rust, cracks, loose seams, or gaps. Carefully look for any peeling or curling shingles near the chimney and signs of water stains indoors around the ceiling or walls adjacent to the chimney.
For a safe DIY examination, use binoculars from the ground or a sturdy ladder to inspect flashing without stepping on fragile shingles. If flashing looks damaged, or if you notice water stains inside the home, it’s wise to call a professional roofer. When discussing the repair or installation with a contractor, ask if they will use metal flashing compatible with your shingles and local climate to ensure durability and code compliance. Also, inquire whether the counter flashing will be properly embedded or sealed into the chimney’s mortar joints to prevent future water infiltration. Proper installation is crucial because even minor gaps can cause leaks over time, affecting your roof and home’s interior.