Chimney Crown Repair vs. Rebuild: How to Decide

The short answer: a chimney crown can be repaired when it is still one solid, well-sloped slab with hairline or surface cracks, and it should be rebuilt when it is broken into pieces, crumbling, too thin, flat, or missing the overhang that keeps water off the brick. In Seattle, where the wet season from October through March brings roughly 29.65 inches of rain (about 73 percent of the yearly total), the crown is the single part of a masonry chimney that takes the most water. Getting this decision right is the difference between a small job now and a much bigger masonry job in a few winters.

We look at four things to decide: how deep the cracks go, whether the crown is still bonded to the brick below it, how the crown was built in the first place, and what the rest of the chimney top looks like. Below is how we walk through that on a roof in Seattle, Tacoma or Everett, and what each path costs to start.

What is a chimney crown, and why does it fail here?

The crown is the sloped slab at the very top of a masonry chimney. It covers the brick and fills the space around the clay flue tile, and its job is simple: shed water away from the chimney and off the edges so it never soaks into the brick or runs down the flue. A properly built crown is a few inches thick, slopes away from the flue on every side, overhangs the brick with a drip edge, and has a small expansion gap around the flue tile so the tile can move with heat without cracking the slab.

Many Seattle chimneys do not have that. Seattle's median home was built in 1976, and Tacoma's in 1967, so a large share of the chimneys we see are original masonry from the 1920s through the 1970s. A lot of those crowns were simply the last batch of mortar from the day the chimney was finished, troweled flat across the top. Mortar is not concrete. It is thin, it has no reinforcement, it has no overhang, and it cracks as soon as the flue tile expands with the first few fires.

Then the Puget Sound climate goes to work. Once a crack opens, water gets in and sits. Winter lows at Sea-Tac average around 37 degrees in December, January and February, and Seattle sees about 60 days a year where the temperature touches freezing. That is the worst pattern for masonry: wet, freeze, thaw, wet again, over and over. The Brick Industry Association notes that water in saturated masonry expands when it freezes, and repeated cycles cause cracking, spalling and disintegration. The crown is the first thing that breaks, and then the water goes into the brick and mortar joints below it.

When a chimney crown repair is enough

Crown repair means sealing and coating a crown that is still structurally sound. We clean the surface, fill the cracks with a flexible crown sealant, and coat the whole top with an elastomeric crown coating that bridges hairline cracks and stays flexible through heat and cold. Done right, it turns a cracked-but-solid crown back into a watertight one.

A crown is a good candidate for repair when:

• The cracks are surface cracks. Hairline cracks, crazing, or a few narrow cracks that do not go all the way through the slab.
• The slab is still one piece. If we press on it, nothing rocks or shifts. No chunks are loose or missing.
• It has real thickness and slope. A crown that is at least a couple of inches thick and actually sheds water can be sealed and expected to hold.
• The brick under it is dry and sound. No spalled brick faces, no soft mortar joints in the top courses, no white efflorescence stains running down from the top.
• The flue tile is intact. The tile sticking up through the crown is not cracked or broken off.

This is the less expensive route and it is the one we recommend whenever it will genuinely hold. If you are searching for chimney crown sealing in Seattle, this is the service you are looking for, and you can read more on our chimney crown repair page.

When the crown needs to be rebuilt

A rebuild means removing the old crown and forming and pouring a new one in concrete, with proper slope, a drip-edge overhang past the brick, and a bond break around the flue tile. It is more work, but it solves the problem instead of covering it.

We recommend a rebuild when:

• The crown is in pieces. Cracks go all the way through and sections move independently. Sealant cannot hold separate chunks together.
• It is crumbling. If the surface comes off in your hand or we can see gravel and sand where the top should be, the material is gone.
• It is a mortar wash. A thin, flat smear of mortar is not a crown. Coating it is coating a slab that will keep cracking underneath the coating.
• There is no overhang. Without a drip edge, every drop of rain runs straight down the face of the brick. Coating the top does nothing for the walls.
• Water has already gone below. Spalling brick, loose top courses, or staining inside the attic or on the ceiling near the chimney tells us the crown failed a while ago. A new crown is part of a repair that may also include repointing the top courses or a broader chimney repair.
• The flue tile is broken at the top. A damaged tile usually gets replaced or extended while the crown is off, which is only possible during a rebuild.

What each option costs to start

Our crown rebuild special starts at $299. Crown repair (sealing and coating a sound crown) is typically less than a rebuild, and we will tell you the number on a free quote before any work starts. Both come with our price match plus a 10 to 25 percent discount if you have a written quote from another company, and our guarantee is simple: if you're not happy, we're not done. We come back and re-do it at no charge.

If another company has already told you the crown has to be rebuilt, we offer a free 2nd-opinion quote. Sometimes they are right. Sometimes a crown that "needs a rebuild" is a solid slab with surface cracks that a good coating will fix for a fraction of the cost. Either way, you will know which one you have.

Is a cracked chimney crown dangerous?

A cracked crown is not an immediate fire or collapse hazard by itself, but it is the start of a chain that gets expensive. Water that gets past the crown soaks the brick, freezes, and pops the faces off the brick (spalling). It rusts the damper. It seeps into the flue and can break down clay tile liner joints. Left alone for enough Seattle winters, the top few feet of a chimney can loosen to the point where a partial rebuild of the masonry is the only fix. That is why we treat crown cracks as a repair-now item rather than a watch-it item, especially heading into November, which is Seattle's wettest month at 6.31 inches on average.

Crown vs. cap vs. chase cover: make sure you have the right part

Homeowners often use these words interchangeably, but they are three different parts:

• A crown is the masonry slab on top of a brick chimney.
• A cap is the metal hood with a screen that sits over the flue opening to keep rain, animals and embers in or out. A crown and a cap work together. See our chimney cap replacement page.
• A chase cover is the flat metal lid over a framed, sided chimney chase on a factory-built fireplace. Homes in newer Renton, Redmond and Gig Harbor subdivisions usually have a chase cover, not a crown.

If your chimney is wood-framed and covered in siding, you do not have a crown to repair; you most likely need a chase cover replacement instead.

What to do next

You do not need to get on the roof to figure this out, and we would rather you did not. Look at the chimney top from the ground or a window with binoculars, or from a neighbor's upper floor. Take a photo if you can. Then:

• Call us at 206-453-2045 or request a free quote online. Tell us what you see: cracks, missing chunks, white stains, water inside.
• We inspect the crown from the roof, photograph it, and tell you plainly whether it is a repair or a rebuild and why.
• Same-day service is often available across Seattle, Tacoma, Everett and the rest of King, Pierce and Snohomish counties.

We serve the whole road-accessible Puget Sound from our office in Renton, including Seattle and Tacoma. Certified and insured, safe and green materials, satisfaction guaranteed.

Related

• Do I Need a Chimney Cap? (Yes — Here's Why in Seattle)
• Rust Stains Running Down Your Chimney? It's Probably the Chase Cover
• Chimney Crown Rebuild service