The Chimney Crown: The Part That Fails First on Old Hartford, CT Stacks
The crown is the small concrete or mortar cap at the very top of the chimney, and on Hartford's older stacks it is usually the first part to fail. Here is what it does, why it cracks, and why it matters more than it looks.
What the crown is and the job it does
Most homeowners have never given the chimney crown a thought, partly because it is the one part of the chimney you cannot see from the ground or the room. The crown is the slab of concrete or mortar at the very top of the chimney, the surface that covers the top of the brick masonry and slopes away from the flue opening in the middle. Its job is simple and important. It seals the top of the masonry against the weather and sheds rain and snowmelt away from the chimney, so water runs off the sloped surface and drips clear instead of soaking into the brick and the joints below. A sound crown is the chimney's umbrella, and like an umbrella, you only notice it when it fails.
On a well-built chimney the crown overhangs the brick slightly, with a drip edge so water falls clear of the masonry rather than running down the face, and it is made of a material that can take the weather. The reality on many older Hartford chimneys is more modest. A great many were finished with a thin mortar wash rather than a proper poured concrete crown, and a thin mortar crown does not have the mass or the resilience to take generations of Connecticut winters. That is a large part of why the crown is so often the first thing to go on the city's older stacks, and why crown trouble is one of the most common findings on our inspections.
Why the crown cracks, and what happens when it does
The crown fails for the same reason the rest of the masonry does, only sooner, because it is the most exposed surface on the most exposed structure on the house. It takes the rain and snow directly, it bakes in the summer sun, and above all it goes through the freeze-and-thaw cycle harder than anything below it. Water soaks into the mortar or concrete, freezes, expands, and opens a crack, and once a crack exists, more water gets in, freezes deeper, and widens it. A thin mortar crown can begin to break apart within a relatively short span of Hartford winters, and even a proper concrete crown will eventually craze and crack under enough cycles.
What makes a cracked crown more serious than it looks is where the water goes once the crown stops shedding it. Instead of running off, water now pours down through the crack into the very top of the chimney, soaking the masonry from inside and running down into the flue. From there it does double damage. It attacks the brick and joints from the inside while the weather attacks them from the outside, which accelerates the spalling and the open joints lower down the stack, and it runs into the flue, where it can rust the damper and deteriorate the liner. A cracked crown is very often the hidden cause behind brick damage and water stains that show up well below it, which is why we always look at the crown first when masonry trouble appears.
- The crown is the sloped slab that caps the top of the masonry
- Its job is to shed water clear of the brick and joints below
- Many older Hartford stacks have only a thin mortar wash crown
- Freeze-and-thaw cracks the crown sooner than the rest of the masonry
- A cracked crown feeds water into the stack and down the flue
Catching it early and fixing it right
The good news about the crown is that catching it early keeps the fix small. A crown with fine cracks that has not yet let serious water into the structure can often be sealed or repaired, restoring its ability to shed water for a modest cost. A crown that has broken apart, or that has already fed enough water into the stack to start the spalling below, usually needs to be rebuilt, poured properly this time with the overhang and the slope it should have had to begin with. The difference between those two jobs is mostly a matter of how long the cracked crown was left to work, which is the whole argument for looking at it before it has done its damage.
Because the crown sits where no homeowner can see it, the only practical way to catch it early is during a routine inspection or sweep, when we are already up there and can put a photo of the crown in front of you. That is exactly why we look at the crown on every visit, not just when there is an obvious problem, and flag a cracking crown while the repair is still small. If your older Hartford chimney has gone years without anyone looking at the top of it, the crown is one of the first things worth checking, because it is both the most likely part to have failed and the one whose failure quietly drives so much of the damage below.
The crown is the part of your chimney you will never see and the part most likely to be quietly failing, and catching it early is the difference between a seal and a rebuild. We look at the crown on every inspection and show you the photo. Call 860-470-8437 to have us check the top of your Hartford chimney before the next winter.
Call 860-470-8437 and we will read the chimney honestly and quote it in writing.