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I once heard an old timer say, “No self respecting mason would put a metal chimney cap on a chimney.” He believed that a concrete cap was better because there is a saying that four inch thickness of concrete provides the same weatherproofing effect as 6mm of poly membrane. In our experience, this could not be farther from the truth.
Kavanagh Masonry has performed chimney repairs all over Ottawa and surrounding area. Nine times out of ten, the cap in disrepair is built using mortar or concrete, which caused it to fail. However, it is a rare occurrence to find a chimney that needs repairing if it has a properly fitted steel cap.
In our opinion, the difference between a poorly built chimney, which will need repairs after only a few years and a well built one that will last decades, all comes down to the materials used for the chimney cap.
Why Concrete and Mortar Caps Fail
A chimney rebuilt with a cap made of a sloping mortar is the worst cap you can have. The mortar will act like a sponge soaking up all the water from snow and rain. With freeze thaw cycles, cracks will develop opening your chimney up to letting in more water creating further damage.
A similar story can be said for a chimney cap made out of concrete. While it is more water resistant, concrete typically always cracks when it is bonded to a material with a different expansion rate, in this case, brickwork. When the concrete starts to show signs of damage, the bricks below it often will start to crack and the damage worsens over time as more moisture is allowed in.
Many concrete caps are also poured without forming a drip key underneath it. This causes water to run directly down the brickwork anytime it rains which can lead to brick spalling, drastically reducing the life of the chimney. For more information on the importance of drip keys, please visit our Custom Window Sills page or our Blog post on the Importance of Drip Keys.
How our Caps are Made Better
At Kavanagh Masonry, all of our chimney repairs and chimney rebuilds are topped with a 20 gauge steel chimney cap built custom ordered to fit your chimney by a skilled sheet metal tradesmen. The cap is enamelled with the colour of your choosing to best match your roof flashing. The enamel also prevents the steel from corroding. These caps are placed on top of a brick chimney crown. A brick chimney crown offers a decorative appeal and acts as an umbrella for the chimney to keep the brickwork below better sheltered from the elements.
All of our custom made caps provide superior waterproofing than those built from concrete or mortar. Each cap is fabricated using corrosion resistant rivets, waterproofing sealants and with a one inch drip edge to wick the water away from the brickwork below. The cap is bonded to the brickwork using heavy duty construction adhesives and the flue liners are sealed with some of our favourite exterior caulking products.
Kavanagh Masonry is an Ottawa based Masonry Contractor specializing in chimney repairs and chimney rebuilds. For more information on our chimney repair services, please visit our Chimney Rebuild service page or if you’re ready to get your chimney fixed, reach out to us on our Request a Quote page.
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