Leaking chimney crown
My chimney crown is leaking.
It is concrete. And it has been repaired a couple times before. It has cracks.
I can't rebuild or replace it right now.
It is about 24" x 36" with a clay pipe exits in the center with a stainless style cap on top of the clay pipe.
I need some options to fix the cracks and leaks in the concrete crown.
I tried calking for cement but it did not last long. I could put an inch of concrete across the top of it. I could put a chimney wash of copper or stainless steel over it.
Are there any other options? Products?
Are there good sealers I can paint the concrete with and the brick work that will withstand the heat and weather conditions?
Looking for what options I have.
Look at the mortar joints above the roof line as they are prone to wear.
The best option and permanent one, is to have a stainless chase fabricated to cover the existing crown about $400 for the size you mention.
Your next best long term option is casting a new crown in place though this will take a considerable amount of work and is very messy. A 24X36 crown + 2 inches of overhang with a slope of 2-3" per linear ft with minimum thickness of 2.5" equates to over 200lbs of concrete. I have done this before with success and if you want to go this route I can guide you through it.
CrownSeal and Chimney RX make a brushable elastometric membrane though this is a temporary fix at best no matter what the packaging says how long it should lasts. The coating is basically a thinned elastometric caulk that can be applied with a brush.
I dislike this method for many reasons starting with your crown most likely being cast incorrectly in the first place with no overhang, kerf, adequate slope and unbinded from the chimney itself, no gap between the flue,etc.. these issues alone combined with the leaking crown can deteriorate brick at a rapid pace.
If you live in a part of a country that experiences freezing temps the deterioration of the brick can be unrepairable over just a few seasons by way of spalling.
Another reason that makes this method of repair even more temporary is this coating does not prevent the expansion and conctraction of the clay flue that is most likely contacting your crown causing it to crack when your fireplace is being used.
Concrete and mortar have different movements when subjected to freeze/thaw cycles and if even partially bound will produce hairline cracks that will grow as time goes on. This is the same premise why your application of a layer of concrete to cover the crown will eventually crack as it will be partially bound to the existing concrete that is of a different mixture than that of you will apply.
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