Chimney Construction Resources
Chimney Construction Literature
The Brick Industry Association (http://www.bia.org) has published some wonderful technical information concerning the construction, design and maintenance of chimneys. I recommend that you go to the Technical Notes section of their web site and read the following articles:
Cement Stable Chimney Caulks
Believe it or not, there is a huge difference between silicone caulks. The word silicone, when used with caulk covers a broad range of different ingredients. Some of these ingredients actually begin to break down in the presence of alkaline substances. Guess what concrete and brick mortar have in high abundance? You're right! Alkalines!
Well, there are silicone caulks that are not harmed by alkaline substances. These are the silicone caulks that contain a high amount of silanes. Silanes are a member of the silicone family. As you might imagine, you will never see the word silane on the side of a caulk tube. So how do you know? Well, the silane silicone caulks usually are the ones with the longest and best warranty.That is one way to shop for them.
Also, quite a few manufacturers actually identify their cement stable silicone caulks as concrete caulk or mortar patch caulk. The major brand name manufacturers almost all have a line of these masonry repair caulks and clearly label them for this purpose.
Filling Large, Deep Voids
The space around a chimney crown might be very deep. One could use three, four or maybe five tubes of very expensive caulk. The professionals, who caulk cracks like this, use a caulk backing material. This is simply a foam product which fills the void to within 3/4 inch of the surface. The remaining gap is then filled with the caulking material.
The following manufacturers make cement stable silicone caulks. Look for their products at your local home center.
- Dow Corning
- Franklin International Titebond
- GE Silicones
Repairing an Existing Damaged Crown
OK, after reading this bulletin you decide to get up and look at your chimney crown. After the inspection you determine that it needs some attention. Yes, I know there is no overhang with a drip kerf. Also, the bricklayer went and poured the cap right against the flue liner. What a goofus! Should you get the sledge hammer out and start over? Maybe not.
I am aware of a repair method that may allow you to install a waterproof system right over the top of your existing chimney crown. It is ChimneySaver's CrownSeal.
Evidently, this system is installed by chimney sweeps and chimney repair specialists all across the nation. It is not a DIY project. The system works by applying a special waterproof flashing material directly on top of your existing crown. A flexible expansion material is placed beneath this flashing against the edge of the flue liner. A special waterproof coating is then applied on top of the flashing to finish off the job. The completed repair looks just about the same as your crown before the repair was started.
Would you like names of individuals close to your home who can install it? If so, go to the ChimneySaver web site and type in your zip code!