Chimney Chase Cover Repair in Los Angeles

A factory-built fireplace, also called a prefab or zero-clearance fireplace, is a metal firebox that vents through a metal flue pipe. Where the pipe runs up an outside wall, it is boxed in with a wood-framed chase finished to match the house. The chase cover is the lid on that box, with a hole for the pipe.

Many original chase covers are flat sheets of galvanized steel. Flat metal does not shed water well, and a thin sheet sags a little over time, so rain collects in the middle. The zinc coating that protects galvanized steel wears through fastest where water stands, and once it is gone, the steel rusts.

Rust holes let water into the chase, where it runs down the flue pipe and the framing. Some of it reaches the fireplace; some of it soaks into the wood. Rust streaks on the siding are the visible part of the same process: rusty water running off the edge of the cover.

Repair is reasonable when the cover is solid and the problem is local: surface rust that has not pitted the metal, a seam or storm collar whose sealant has failed, or a loose fastener at the edge.

Replacement is the answer when the cover has rust holes, has sagged into a dish that holds water, or flexes when pressed. Patching a thin, dished cover leaves the cause in place, and the next hole appears somewhere else.

Material. Galvanized steel is the cheaper option and the one that usually failed. Stainless steel resists corrosion far better and is the common replacement choice. Copper lasts longer still and weathers to a brown-green patina, which suits some houses and not others.

Shape. A cross-break chase cover has shallow diagonal creases pressed from corner to corner, forming a low peak around the flue hole so water runs outward instead of pooling. A sloped or pitched cover goes further, with the top formed at an angle. Either is a large improvement on a flat sheet.

Edges. The skirt is the part that folds down over the outside of the chase. A drip edge, a small outward kick at the bottom of the skirt, throws water clear of the siding instead of letting it run down the wall.

A cover that has leaked for a long time can leave the framing, sheathing and siding of the chase soft or rotted. Chimney chase repair of that kind is carpentry and siding work, and a general contractor or carpenter is usually the right trade for it. It needs to be done before the new cover goes on, because a cover fastened to rotted wood will not stay put.

Water that has reached the fireplace itself is a separate question. Rust on the metal firebox or damaged refractory panels, the heat-resistant liners inside a factory-built firebox, are covered on firebox repair. Some manufacturers also have guidance on whether a water-damaged unit can stay in service, and the installation manual or the manufacturer is the place to check.

Salt air. A chase cover is a large, flat piece of thin metal facing the sky, which makes it more exposed than a chimney cap. On a house near the ocean, airborne salt tends to break down a galvanized cover's coating faster than it would inland, and standing water on a flat cover speeds that up. On a coastal house, stainless steel is the sensible starting point for a replacement.

Tract-era fireplaces. Where a house was built from the 1970s onward, particularly as part of a tract subdivision, it may have a factory-built fireplace in a framed chase rather than a masonry chimney. If that is your house, and the original cover has never been replaced, it is worth a look from the ground after the next rain.