Chimney Crown Repair

What the crown does

The crown covers the top of the brick, around the flue tiles, and directs rain and snowmelt away from the chimney. A well-built crown slopes away from the flue, extends past the brick on every side, and has a groove or edge underneath so water drips off instead of running back down the face.

The crown is often confused with the cap. The cap is the metal cover over the flue opening; the crown is the masonry around it. Our guide to crown vs. cap shows the difference.

From the ground, the crown is often hidden by the cap and the angle of the roof. That's why crown damage tends to be found during an inspection from the roof, or only after it has started to damage the brick below.

Why crowns fail

Many crowns aren't built to do their job in the first place. A common shortcut is a layer of mortar troweled across the top of the brick, flush with the edges. Mortar mix isn't meant for that, and with no overhang the water runs straight down the brick.

Even a well-made crown moves. The flue tile heats and expands; the crown and brick move differently with temperature. The Brick Industry Association's guidance on residential chimneys recommends a bond break between the crown and the masonry, and an overhang with a drip, so the crown can move without cracking the brickwork. When a crown is cast tight to the flue tile with no room to move, cracks around the flue are common.

Signs your crown needs attention

• Cracks across the top or around the flue tiles
• Pieces of concrete or mortar on the roof below the chimney
• Spalling or efflorescence concentrated on the top few courses of brick
• Water or rust on the damper after rain
• A crown that's flush with the brick, with no overhang

These point toward the crown, but water at the top of the chimney can also come from an uncapped flue or worn brick. The assessment sorts that out.

How we assess it

We look at the crown from the roof when it's safe: its shape, slope, thickness at the edges, overhang, and every crack, including fine ones around the flue tiles. We check the brick just below for water damage, and look at the cap at the same time. Inside, the damper and the top of the flue tell us whether water is getting down the chimney; a chimney camera helps where the flue allows. If a leak is involved and the source isn't clear, a controlled water test can isolate the crown from other parts.

You get photos of the crown and our findings, with the options, before any repair is scheduled.

Coating, repair or rebuild

Crown coating

For a crown that's sound in shape with fine surface cracks, a flexible crown coating made for chimney crowns can seal the cracks and the surface. It works on a crown that's already shaped to shed water. It doesn't fix a crown that's flat, thin or breaking apart.

Crack repair

Wider cracks can be cleaned out and filled with a crown repair material before coating. The space around the flue tiles needs a flexible seal so the tile can expand without cracking the crown again.

Crown rebuild

A crown that's crumbling, too thin, flat, or has no overhang is better replaced. A rebuilt crown can be formed with a slope, an overhang beyond the brick and a drip edge underneath, with room left for the flue to move.

Our guide to crown coating vs. rebuild goes through the decision in detail.

What a well-built crown looks like

When a crown is rebuilt, its details matter more than its thickness alone. These are the features we plan for:

• A slope from the flue tiles down to the outer edge, so water runs off instead of sitting on top.
• An overhang past the face of the brick on every side.
• A drip edge, a groove or edge on the underside of the overhang, so water falls clear instead of curling back under onto the brick.
• Room for the flue to move. The flue tile heats up and grows; the crown shouldn't be locked tight against it. A flexible seal goes in the gap.
• A separation from the brick below, so the crown and the chimney can move independently, as the Brick Industry Association's guidance recommends.
• Flue tiles projecting above the crown, so a cap can be fitted and water doesn't run into the flue.

Precast crowns and crowns formed in place can both work when these details are right.

Limits and what affects the scope

• A coating can't make up for a crown with the wrong shape or no overhang.
• Crown materials need dry weather and suitable temperatures to cure.
• The number of flues and the crown's size affect the work.
• Damaged brick under the crown may need repair at the same time. See masonry repair.
• Adding a cap keeps rain out of the flue, which the crown can't do.

Next step

If you've spotted cracks on top of the chimney, debris on the roof or damage at the top courses, request an assessment. A photo from a window or a drone image helps if you have one. A team member will contact you to confirm a time.

Request a crown assessment

Questions homeowners ask

Sources

1. Brick Industry Association, Technical Note 19B: Residential Chimneys, Design and Construction (copy hosted by InspectAPedia)