Chimney Flashing Repair in Rancho Palos Verdes: Written Report, Licensed Technicians

A homeowner in the Crest Road area called us last February after noticing a water stain spreading across the ceiling of their upstairs bedroom. The stain only appeared during heavy rain, and it dried out completely by mid-March. They'd assumed it was a roof issue and had a roofer out twice. Both times, the roofer found nothing wrong with the shingles. The problem sat dormant through the dry months, then returned the following December, darker and wider. By the time they reached Stonebridge Chimney Works, they were worried about mold behind the drywall. Their chimney sits on the uphill side of a 1970s ranch-style home, right where the roofline meets a steep slope. That geometry matters.

What they described is one of the most common misdiagnoses we see along the Rolling Hills border and across the Palos Verdes Drive North corridor. The leak pattern follows SoCal's rain season perfectly: water intrusion from late November through March, then months of nothing. Homeowners assume the problem resolved itself. It didn't. The flashing around the chimney had been failing for at least two seasons, but the damage only became visible when consecutive storms pushed enough water behind the counterflashing to saturate the underlayment. Their situation isn't unusual for this part of Rancho Palos Verdes, where many chimneys were originally flashed with aluminum that's had 40 to 50 years of thermal cycling and coastal moisture working against it.

We ran a Level 2 inspection per NFPA 211 standards, which includes a camera scan of the flue interior and a close examination of all accessible chimney components. The flue itself was in decent shape. The real problem was at the roof-to-chimney junction. The original step flashing, aluminum L-shaped pieces that weave between each course of shingles and the chimney wall, had corroded and pulled away from the masonry. Corrosion had eaten pinholes through two of the lower step pieces. The counterflashing, the metal strip embedded in the mortar joints that overlaps the step flashing, had cracked loose at the reglet. Water ran behind both layers and into the roof deck. We also found the chimney lacked a cricket, a small peaked diverter built on the uphill side to route water around the structure. On sloped lots along Palos Verdes Drive North, a missing cricket is almost a guarantee of eventual leaking.

We replaced the step flashing with lead-coated copper, which holds up far better than aluminum in Rancho Palos Verdes' salt-heavy air. We cut new reglets into the mortar joints, set the counterflashing with high-temperature sealant, and installed a properly sized cricket covered in matching roofing material. The whole job took a day and a half. Lead-coated copper costs more upfront than aluminum, but it resists the galvanic corrosion that eats through dissimilar metals on a masonry chimney. For homes in the Crest Road area and along the Rolling Hills border, where ocean moisture is constant, that material choice is the difference between a 10-year fix and a 30-year fix. If your chimney flashing has never been replaced on a home built before 1985, the original materials are past their expected life. Get it inspected before the next rain season, not during it.