How to Repair a Chimney Crown in 4 Simple Steps
Add years to your chimney's life by catching and patching small cracks
- Ladder
- Tape measure
- Canvas tarp
- Caulk gun
- Putty knife
- Duct tape
- Quick-setting cement repair caulk
- Crown sealant
- Water-repellent coating for chimneys
A chimney's crown is integral to its structure. This protective top cement layer covers the porous brick below to prevent moisture from entering the chimney and causing damage. Over time, small cracks and chips can compromise a chimney crown's function. If you catch the problem early enough, you can repair the chimney crown yourself before replacement is necessary. Our step-by-step guide explains how to repair a chimney crown.
Prepping to Repair a Chimney Crown
Before you start your repair, you'll need to climb on the roof to inspect the existing crown. Working on a roof can be dangerous, so ensure you have a spotter to hold the ladder for you. Look for spider cracks and missing chunks, which are telltale signs of a crown that's susceptible to moisture and in need of replacement.
Wrap duct tape around the crown, about a quarter inch below the edge of the seam where the crown meets the brick. Then, wrap duct tape around each flue liner about one inch above the crown. Lay out a canvas tarp around the base of the chimney on the roof to protect the shingles from any drips of sealant.
How to Repair a Chimney Crown
To repair a chimney crown, you’ll need to clean and level the surface before applying a sealant specifically designed for chimney crowns. Once the crown is dry, you can use a water-repellent coating to add extra protection.
Clean and Prepare the Crown
Look for loose pieces around the flue liner and carefully chip them off by hand. Then, use your stainless steel wire brush to scrub away any grime, stains, and remaining loose material from the crown.
Patch Holes With Quick-Setting Cement
This step is only required if there are holes and dips left over after removing loose pieces. If so, patch them using a quick-setting cement repair caulk and caulk gun, then follow the instructions on the container to allow appropriate time for the cement to set.
Apply Chimney Crown Sealant
Seal the crown using your crown sealant product. Scoop sealant with your putty knife and spread it onto the crown. Then use your nylon brush to level out the sealant until smooth.
Seal the Bricks With Water Repellent Coating
Once your sealant has dried, use your spray pump to apply a water-based elastomeric coating designed for chimney crowns. Start at the bottom of the chimney from where you laid your canvas and work your way up. After you've coated the entire chimney, wait five minutes and repeat the process.
After about an hour, your coating should be dry and you can remove the tape and tarp.
DIY vs. Hiring a Pro
The cost to repair a chimney crown is less than $100 when you DIY since all you’ll pay for is the materials. Compared to the $400 or more you’ll pay a pro to do the work, the DIY approach will save you a significant amount of money.
However, while chimney crown repair is a relatively simple project, any task that involves climbing on a roof is inherently dangerous. Skip the DIY and hire a pro if:
You lack the proper equipment
You don't have a partner to spot you while you're on the ladder or roof
Your roof design makes your chimney crown particularly difficult to access
You can hire a local chimney cap replacement specialist or general chimney service to handle the job.
You should repair your chimney crown if it has short hairline cracks or small chips that you can seal over. You should have a professional completely remove your old chimney crown and replace it by building a new one if you have severe structural cracks or deep dips that hold water. Sealant alone won’t be able to handle that type of damage.
A high-quality chimney crown should last anywhere from 50 to 75 years if it’s been constructed properly. If the brick around the chimney flue was not prepared properly before installation or the crown was otherwise poorly constructed, moisture buildup could cause it to break down in less than 20 years, leading to a more costly rebuild down the line.
You should use cement for a chimney crown. The purpose of the chimney crown is to protect the mortar below from water damage and the effects of weather. For this reason, chimney crowns should only be made using cement. When repairing a crown, use caulks and sealants designed for cement repair rather than mortar repair.
A chimney crown needs to be sealed as part of its initial installation. If, later on, small cracks begin to form in the chimney crown that aren’t serious enough to warrant crown replacement, sealant is a viable option for repairs. Sealing hairline cracks will help to prevent additional moisture from leaking into the chimney through the crown.
No, a chimney crown is not the same as a chimney cap. A chimney crown is a flat cement area on top of a masonry chimney. It starts where the masonry part of the chimney ends at the very top and domes upward toward the flue opening. A chimney cap sits on top of the crown over the flue. It is usually made of metal and allows smoke to escape without letting in rainwater.
