Chimney Sweep in Casa de Oro-Mount Helix, CA

It can be either, and on Mount Helix it's often both. A flue coated with creosote and debris has less draft to work with, so cleaning is the first step. But tall exposed stacks on windy hillside lots also get true downdraft: wind hitting the ridge rolls over the crown and pushes air back down the flue. We check the flue's condition and height, look at how the cap and spark arrestor are shaped, and tell you honestly whether a cleaning fixed it or whether the termination needs changing. Homes here with more than one flue in a single stack can also cross-communicate, where one hearth spills smoke through a neighboring flue.

Crowns and flashing. The stacks on these 1940s-70s masonry fireplaces are tall and fully exposed, and winter storms load them directly. Crown cracking is the most common finding, and once water gets into a crack it works down through the brick or stone. The second is flashing failure where the chimney meets a steep roof pitch, which shows up as staining on the ceiling near the chimney chase rather than at the firebox. Third is spark arrestor screen that's rusted through, crushed, or missing entirely, which matters given the chaparral on the slopes.