Chimney Flashing Repair in Thousand Oaks

The call usually goes like this. After a storm, a ring of brown or yellow appears on the ceiling near the chimney, or the paint on the chimney breast starts to bubble. The homeowner calls a roofer, the roofer smears some sealant around the base of the chimney, and the stain comes back next winter. That pattern is common because flashing is a two-trade joint. The roof belongs to the roofer and the chimney to the mason, and the flashing ties one to the other. Done properly it is a system of two layers. Step flashing is a series of L-shaped pieces woven into the roofing along the sides of the chimney, each one overlapping the one below it like shingles. Counter flashing covers the top edge of the step flashing and is cut into the mortar joints of the brick, so water running down the face of the chimney is turned out over the step pieces and onto the roof. Without the counter flashing set into the masonry, water runs down behind the step flashing and straight into the house. A bead of caulk across that joint lasts a season or two in the sun before it cracks and pulls away, which is why sealant on its own keeps failing.

When we trace a stain, we start inside, note where the water shows and how far it is from the chimney, then go to the attic. Wet or darkened sheathing and rafters beside the chimney, especially on the uphill side, point to the flashing. Dry wood around the chimney with water appearing lower down points elsewhere, often into the masonry itself. On the roof we look at each part of the flashing: whether the counter flashing is let into the mortar or just glued to the face of the brick, whether the step pieces are intact and properly lapped, whether the front apron is lifted, and whether the uphill side has a cricket. If the leak is still unclear we run water in stages, low to high, with someone watching inside. That takes the guesswork out of it, and it means the repair goes where the water actually enters. The findings go into a report with photos, and the repair is quoted in writing before any work is booked. If the masonry is part of the problem, our chimney masonry repair page covers that half of the job.

Many houses in Thousand Oaks, Newbury Park and Westlake Village have concrete or clay tile roofs, and tile changes the flashing job. The tiles themselves are not the waterproof layer, the underlayment beneath them is, so the flashing has to direct water onto that layer and the pan flashing under the tiles, not just onto the tile surface. Tile also has to be lifted and reset carefully around the chimney, and broken pieces replaced to match. On composition shingle roofs the step flashing is woven into each course as the shingles go back down. Either way, the work only lasts when the counter flashing is cut into the mortar joints, called reglets, and sealed there, rather than surface-mounted with screws and caulk. We use metal that holds up in this climate and does not react with the other metals on the roof. Where an old roof is near the end of its life, we will say so, because new flashing on a roof that is about to be replaced may need to be redone with the new roof.

The uphill side of a chimney deserves special attention. Water running down the roof hits the back of the chimney and has nowhere to go but sideways, and leaves and debris collect there too. Building codes call for a cricket, also called a saddle, on chimneys wider than 30 inches measured across the roof slope: a small peaked structure behind the chimney that splits the flow and sends it around both sides. Many older chimneys were built without one, and the back corners are where we find the most rotted sheathing. Adding a cricket is part of many of our flashing repairs. Flashing work is quoted in writing after we have seen the roof, because the materials, the roof type and the extent of hidden damage all change the scope. Rotten sheathing gets replaced before new flashing goes on, never covered over. Once the joint is sealed, a chimney cap installation and a sound crown complete the job of keeping water out from the top down.