Your local chimney and fireplace service in Tallulah-North Shore

Dark streaks at the top of a chimney and a green film on one face of the brick can look alike from the ground, but they mean different things, and cleaning either one the wrong way can do more harm than the stain. Black staining on the top courses can come from smoke and soot leaving the flue, and where the crown has no overhang or drip edge, runoff carries that residue down the face.

A green or dark film on a face that stays in shade can be organic growth such as moss, algae or lichen, which the Brick Industry Association ties to masonry that stays damp. A green stain on light-colored brick can also be vanadium salts from the brick itself, which is a different problem that takes different cleaners.

So the first step is working out which one you have, and the second is finding why the brick stays wet, whether that is a missing cap, a crown without a drip edge, open mortar joints, a gutter spilling against the stack or shade that keeps the face from drying. Cleaning follows the Brick Industry Association's guidance on cleaning brickwork.

We try the method on a small trial area first and let it dry before judging it, choose the gentlest method that works, soak the brick before any cleaner goes on, keep the water pressure low, and avoid unbuffered muriatic acid and abrasive blasting, which can etch the brick and the joints. Plants and painted trim near the chimney are covered while the work goes on.

Once the water source has been fixed, a water repellent may be worth adding, and the estimate says whether it is. A stain that comes back after cleaning points to water that is still getting in, so the estimate treats the leak before the looks. Each line names the stain, its likely cause, the cleaning method and the repair that stops it returning.

If stains are spreading on the chimney at your Tallulah-North Shore home, call (904) 920-5495, and our masonry pros will tell you what they are at a free inspection.