Chimney Crown Repair: Why Water Gets In and What to Do

If your chimney is leaking, spalling or shedding mortar near the top, look at the crown first. It is the most exposed spot on the whole building, and when it fails, everything under it gets wet.

What does a chimney crown do?

In plain terms, the crown is the top layer that covers the brick at the very top of the chimney and sheds water outward instead of letting it sit or run inside. It is separate from the metal or clay cap that sometimes sits over the flue opening, which is a different part with a different job. People use the two words loosely, and contractors do too, so ask which one is meant on any estimate.

The Brick Industry Association notes that the primary function of caps and copings is to channel water away from the building. Because they sit at the most exposed location, a cap built of brick with many mortar joints may be a poor choice compared with concrete, stone or metal (BIA Technical Note 36A). That guidance covers caps and copings on masonry in general. How a particular Chicago chimney was originally topped varies, and specifics such as thickness, overhang and flue details are something a mason has to confirm on site.

Flashing also matters at the base. The BIA lists chimneys among the places where through-wall flashing is installed to collect water and direct it back out (BIA Technical Note 7). If the leak shows up inside near where the chimney meets the roof, that joint is a separate suspect from the crown.

What does a failing crown look like?

• Cracks across the top surface, or pieces missing at the edges.
• Crumbling, sandy or flaking material on the top.
• A gap or loose edge between the top surface and the brick below.
• Mortar joints below the top that are open, washed out or stained.
• Spalled brick faces in the top few courses, or white salt deposits streaking down the sides.
• Water stains on the ceiling or wall near the chimney, especially after rain or a thaw.

Seeing these from the ground is limited, since much of the top is out of view. Binoculars help. Climbing onto a roof to look is not something we recommend.

Can you patch it yourself?

Hairline cracks and small gaps are where owners reach for caulk or a bucket of patch. A surface patch over a crown that is moving, cracked through or sitting on wet or crumbling brick usually will not last, and it can trap water. The crown, the joints below it and the flashing at the roof all work as a system, so a repair has to look at all three. Because the work is at height and involves masonry, it is a job for a licensed mason contractor (City mason license).

The City's Express Permit program lists routine maintenance and repair for masonry walls (City of Chicago), but it does not spell out crown or cap work specifically. Whether your repair needs a permit depends on scope, so confirm with the Department of Buildings before work begins. If masonry is not "maintained weather resistant or water tight," or parts of the exterior are not properly anchored, the City can cite it (City of Chicago code).

What to do next

Photograph what you can see, note where water shows up inside, and have a mason look at the whole chimney, not just the top. For the bigger picture on whether a chimney needs repair, rebuild or tuckpointing, see chimney repair in Chicago, chimney tuckpointing and a leaning chimney. Our masonry crew can inspect it, and the brick and masonry repair guide covers the rest of the exterior.

Common questions

This article explains general rules and common situations in Chicago. It is not legal advice, and City rules change. For a specific property, check with the Chicago Department of Buildings or a licensed professional.