How to Repair a Chimney Crown

Saving a chimney from deterioration and leaking can be as simple as repairing or replacing the chimney crown. The crown of the chimney is one of the most important parts of a chimney. Protecting the bricks, mortar, joints and fireplace, the crown maintains the life and integrity of the chimney.

Difficulty: Moderate

Instructions

Things You'll Need:

• Gloves
• Drop cloth
• Chisel
• Hammer
• Buckets
• Wheelbarrow
• Water
• Hoe
• Shovel
• 2 to 3 bags Masonry Cement depending on the chimney’s size
• 1 to 2 bags of pea gravel
• Trowel

1. Place a drop cloth on the roof to protect it. Take off the broken crown by slowly breaking apart the concrete with your chisel and hammer. Start from the edge. Avoid striking near the flue. Work carefully and there will be no damage to the flue. Place the broken pieces in your bucket.

2. Put one bag of masonry cement and ½ bag of pea gravel in the wheelbarrow. Mix the dry ingredients with your hoe thoroughly before adding any water. This will help create uniformity when you’re ready to form the crown.

3. Mix the new crown on the ground in the wheelbarrow with your hoe slowly adding small amounts of water to your mix. Create the consistency of frosting for your crown mixture. Just before you reach the right thickness pour 1 cup of the bonding agent into your wheelbarrow. Blend completely.

4. Shovel reasonable amounts of cement into your bucket and carry up the ladder. Scoop out the cement with your trowel. Place an even amount onto the chimney, surrounding the entire flue. Keep up a healthy pace but don’t rush.

5. Chop the cement with the edge of your trowel after you place it on the chimney. This releases any bubbles and forms a stronger bond.

6. If your flue sticks out more than 6 inches from the top of the chimney, form your crown about 4 inches high where it meets the flue. If it sticks out less than 6 inches, build your crown 2 inches from the top of the flue.

7. Use your trowel to create a pyramid shape which slopes away from the flue. Place the cement up against the flue and smooth the mortar as you work. Your flue is the center of your crown.

Tips & Warnings

• After crown has dried, paint a vapor permeable water sealant on it so the chimney lets water out but not in.
• Buy a stainless steel chimney cap. Water will run off the edge and not onto the crown.
• Clean all tools as soon as possible.
• Have a helper hold the ladder
• Don't take any unnecessary chances with heights. Only work on your chimney if you can get to it easily and safely.

[dables]

on 9/21/2009 This is a great article but leaves out a point that will destroy the crown quickly putting you back in the same shape as you were previously. Do not put cement in contact with the flue tiles. Put a cardboard spacer between the cement and flue tile. When everything thoroughly dries remove this and fill the gap with silicone. Make it level so water will not stand. This allows the flue tile to expand and contract freely when heated and cooled. If you don't it will crack the crown again and it won't take very long.
Also do not put a Waterseal on the top but as the writer said a breathable water proofer to allow water vapor to pass. They are hard to find but will save lots of trouble.