Chimney and fireplace symptoms
The concrete cap on top of my chimney is cracked
A chimney's concrete cap is the crown, and it often cracks where it was poured tight against the flue tile, letting Portland rain in. The crack is a water problem; tile or brick pieces in the firebox mean no fires until a camera looks.
Updated
What to do right now
Stay off the roof; a crown is a dry-day job with a harness. From the ground, take a zoomed photo of the chimney top and text it to us, then check the firebox after the next rain for water, rust or white crust, which shows whether the crack is letting water through. Concrete chunks in the gutter or on the ground mean keeping people off that side.
Likely causes, most common first
Why crowns crack, most common first, and which repair each points to.
- Most common
The crown was poured tight against the flue tile
The sign: A crack running from the flue tile straight out to the edge of the crown, often one at each corner of the tile, on a chimney of any age.
The fix: The cracks are cleaned and bridged with a flexible coating that moves with the tile, or the slab is re-poured with a gap at the tile when it is past coating. Chimney Crown Repair, from $349
- Common
A mortar wash that was never a real crown
The sign: A thin skim of gray mortar sloped off the top brick with no overhang, crazed and crumbling at the edges, often found on older chimneys.
The fix: The wash comes off and a proper crown is formed and poured, thick in the middle, overhanging the brick with a drip edge underneath. Chimney Crown Repair, from $349
- Common
Years of freezing in a hairline crack
The sign: A crack wide enough to hold a coin, with the brick below it streaked white or spalling in the top courses.
The fix: The crown is rebuilt or coated and the top courses get a breathable water repellent once they have dried, so the brick stops taking the water. Chimney Waterproofing, from $349
- Common
No cap, so rain sits on the crown and inside the tile
The sign: An open flue tile above the crown, a ring of dark, always-damp concrete around it, and water or rust in the firebox after storms.
The fix: A cap on the tile keeps rain off the weakest point of the crown and out of the flue, and goes on with the crown work. Chimney Cap Installation, from $299
Two minutes of safe checks
A crown is out of sight from the yard, so these checks read it from what it lets through.
- Zoom in with a phone or binoculars from across the street: a crown should stick out past the brick with a shadow line under it; a top flush with the brick is a mortar wash.
- Look at the top few courses of brick for white streaks or dark wet patches that outlast the rest of the chimney; the crown above them is leaking.
- After a rain, look up past the open damper with a flashlight: drips, a wet smoke shelf or fresh rust on the damper plate mean water is coming from the top.
- Check the gutters and the ground below the chimney for gray concrete crumbs; a crown that is breaking up sheds them with every storm.
What the crown is and what it is supposed to do
The crown is the sloped slab on top of the chimney wall that sheds rain off the brick and away from the flue. The cap sits above it over the flue opening; the crown protects everything below.
A crown that works is a few inches thick, slopes from the flue to the edge, overhangs the brick with a drip groove underneath, and meets the flue tile at a flexible joint, since the tile heats and grows while the concrete does not.
Some older chimneys have no crown in that sense, only a mortar wash: a slope of joint mortar troweled across the top brick. It is thin, cracks early, has no overhang and can leave an old chimney wet at the top for decades.
Hairline cracks versus chunks missing
The width of the crack decides the repair. Fine cracks in a crown that is otherwise solid, overhanging and well attached get cleaned, filled and covered with a flexible coat that bridges them and moves with the seasons.
A crown with pieces missing, crumbling edges, a gap between it and the brick or a mortar wash underneath is past coating. It comes off, a form is built around the top of the chimney, and a new crown is poured with the overhang, slope and expansion gap the old one lacked.
Why the crown is where Portland leaks begin
Water on a chimney starts at the top, and a crown lying nearly flat under three feet of rain a year offers a hairline crack as the first opening. It can freeze in that crack on about 32 nights a year and pry it wider.
Once past the crown, water runs down between the flue tile and the outer brick, where nothing can dry it. It shows up as white salts on the top courses, rust on the damper, a wet smoke shelf, a stain on an upstairs chimney breast or spalled brick above the roof.
What a crown repair involves
The visit starts with photos from the roof and ends with photos you can compare.
Assess from the roof
We photograph the crown, the joint at the flue tile, the overhang and the top courses, and measure the cracks. Hairline, solid and overhanging means a coat; crumbling, flush or mortar wash means a new crown.
Coat a sound crown
The crown is cleaned and dried, cracks are filled, the gap at the tile gets a flexible sealant, and a flexible coating goes over the whole top and down the overhang.
Pour a new one
The old slab or wash comes off to sound brick, a form is set with the overhang built in, and a new crown is poured with a slope, a drip edge and a bond break at the tile, then left to cure dry.
Cap and protect
A cap is fitted or re-set over the tile, and the top courses are repointed and treated where the old leak reached them. The posted price covers the crown; anything extra is shown in the photos first.
Cracked crown: common questions
Is a cracked chimney crown an urgent repair or can it wait a year?
It can usually wait for a dry window, and that window is the point. Every wet freeze before the repair widens the crack and sends more water down the stack. A hairline crack found in September is a coating job; the same crack after two Portland winters often means a new crown and spalled brick below it.
What is the difference between a chimney crown and a chimney cap?
The crown is the concrete slab across the top of the brick; the cap is the metal hood over the flue opening. The crown sheds water off the chimney, the cap keeps rain, animals and debris out of the flue itself, and a chimney needs both. A cracked crown leaks around the flue; a missing cap leaks down it.
Will a crown coating fix my cracked chimney crown, or does it need a new pour?
A coating works when the crown is still solid, attached to the brick and overhanging it. A flexible crown coating bridges hairline cracks and stays elastic through freeze and thaw. Coating a crumbling crown or a mortar wash soon fails, because the coating cannot hold together a slab breaking apart underneath it.
How do I know the chimney crown is cracked without going on the roof?
Read the chimney from below. White streaks or wet patches in the top courses, concrete crumbs in the gutter, water or rust in the firebox after rain and a top that sits flush with the brick instead of overhanging all point to a failed crown. A zoomed photo from across the street often tells us which repair it is.
Does a cracked crown mean the chimney is unsafe to use?
On its own, no; a crown crack is a water problem, not a fire problem. It becomes a use question when the water it let in has cracked flue tiles, rusted the damper open or dropped brick into the flue, which a camera run checks. Tile or brick pieces in the firebox mean leaving it cold until that look is done.
Related pages
Areas we cover for this
Calls about cracked crown come in from Fairview and Wood Village, Hillsdale, Mt. Tabor and every other part of the metro we serve.
Ready to book a sweep?
Call with what the fireplace is doing, or text a photo of the opening and one of the chimney top, and we will name the service and its posted price before we come out.