Chimney Portland Cement

Photo: Contributed - (Photo: Hugh Cairns)

Your chimney crown is often called a chimney cap. Chimney crowns are almost always the highest thing on your home. Because they are so high up and since most people don't regularly climb on their roofs, chimney crowns are often neglected.

If you have a chimney, you rely on it to channel smoke up and out, but when the chimney's exterior or inside walls fail; you may end up with difficult problems. The freeze-thaw action of colder climates coupled with moisture is usually the culprit that causes the crown to fail. Mortar joints between stone or bricks are likely to flake, wash out or crack after years of exposure to the elements.

If the cement crown is completely missing or beyond repair, replacing the crown is your only option. To replace the crown you must fashion a form for the crown on the outside of the chimney edge. A special mortar is mixed and poured into the form and left to dry for several days. Once the mortar is dry the forms are removed leaving a nice new crown.

If the crown is mostly intact, a synthetic crown sealer may be an option for you. The synthetic sealer acts like a paste that is spread on the surface and dries to an elastic type coating that resembles dry mortar. Even though water penetration can effectively be stopped with a synthetic sealer, no product can restore delaminated bricks. Therefore, flaking or spalling may occur after treatment as a result of previous water damage. Crown sealers usually come with a limited warranty.

Once the mortar crown has deteriorated, rain damage can extend to the mortar holding the bricks together, and the chimney becomes weaker and weaker until bricks - or even whole rows of bricks, start to fall onto the roof or to what's on the ground below, as shown in the picture above. Once this degree of damage has occurred, partial rebuilding of the chimney may become necessary - an expensive repair that can be avoided by maintaining a good mortar crown.

It’s quite amazing that a 5¢ hose washer can cause $15,000 damage, but it can. Recently, a client of mine took possession of his brand new home. The laundry pair wasn’t included in the purchase of the home so he was off to a local supplier to buy them. His purchase included delivery and installation. In the case of the washing machine it included the water supply connections.

Chimney Restoration of the week | The Chimney Swift Ltd.

This chimney services both a wood-burning fireplace and a gas furnace and water heater. The damage, as shown in the photo) was caused by two things.

I- the gas flue is lined with clay tile, which is not water-tight. Moisture venting up the flue is able to escape into the masonry structure and freeze/thaw cycles throughout the winter will damage the brick and mortar joints.

2 - The mortar used when the chimney was originally built is portland cement based and is too hard. It will not compress, and therefore the brick itself must give during expansion and contraction cycles with occur as the chimney heats up and cools down.

We rebuilt the chimney from the roof up and installed a stainless steel liner in the gas flue to contain the moisture from the gas appliances.

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