The mortar crown cap on my chimney needs repair. There is damaged mortar leaving holes against the flue and also hairline cracks. Can you folks recommend some products to do the repair. From what I have read there are different products used for larger holes vs hairline cracks.
Thank You.
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This might be a good question for our Ask the Expert department in the magazine. I'll reach out to one of our mason experts and let you know what he says. Thanks!
Thank You. The person who I hired to paint my house and seal the chimney noticed the damage and took a picture. I'll have him send the picture to me and I'll post it. The top 6 feet of the chimney was rebuilt almost 20 years ago. Original mason did not tie it in to the house framing and it was tilting away from the house.
Here are the pictures.
Could you please send me those original images at [email protected] Thanks!
I sent them.
Thank you.
Jim,
I would replace the crown.
Here is an explanation I found, there are several others. Find one from a masonry site for a lot more detail.
When we built our chimney I used a non-flammable rope between the cap and clay flue as a backer-rod. Topped off with urethane caulk rather than silicone (I think-35yrs….).
Any other repair will be temporary as there needs to be separation between the cap and flue to keep expansion/contraction in manageable.
Edit: link to a cap construction detail
https://www.jlconline.com/how-to/foundations/preventing-chimney-cap-failure_o
And for some good reading and info, peruse this site.
https://www.mha-net.org/
Thank You
This is a response by Mason, John Carrol:
If the crown is crumbling, has structural cracks, or has large dips that hold water, you need to remove the old crown and build a new one. None of those conditions are visible in the photographs you sent.
For your chimney, you should chip off the small loose pieces near the flue liner, then go over the entire crown with a stainless steel brush. Doing this will remove grime and loose material from the surface. If the chips you remove create dips that will hold water, patch them with quick-setting mortar patch. Seal the crack with siloconized acrylic latex caulk.
After the patching materials dry, brush on a water-based elastomeric coating designed for chimney crowns. I’ve had excellent results using Chimney RX Brushable Crown Repair. Amazon.com: Brushable Crown Repair : Home & Kitchen
John,
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Thank You.
Because the top of the chimney takes a beating from the elements over the years, I recommend using type-S masonry-cement mortar, which has an increased amount of portland cement. This mortar is available at your local masonry-supply dealer in 70-lb. bags, and it's fairly inexpensive.
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