Protect Your Chimney From Water Damage Inside and Out
5/6/2010 1:00 AM
Your masonry chimney is vulnerable to attack by water from both the inside and the outside, but there are steps you can take to protect it. The outside of your chimney is exposed to weather all year round. Rain and snow can penetrate cracks in the mortar between bricks or in the mortar cap on top of the chimney. Temperature fluctuations in cold weather will cause water trapped in tiny cracks to expand and contract in a freeze/thaw cycle which can eventually tear your chimney apart. You can protect your chimney from this external aqueous assault by sealing the exterior surfaces and filling cracks with products such as Crown Seal and Crack Magic Crack Sealant. You can also install a chimney cap over the top of your chimney to keep rain and snow from falling inside your flue and on top of the mortar cap. A stainless steel chimney cap not only covers the flue, but it has a screen mesh that acts as a spark arrestor and keeps birds, squirrels, bats and other unwanted visitors out of your house.
Your chimney can be attacked by water from the inside, where it might do more damage to the structure than external moisture. Besides having rain and snow enter your flue from the top, water vapor is carried up the chimney along with other combustion products to be vented to the outside. As the combustion gases rise up the chimney, they will cool enough to condense onto the inside walls of the flue. Water vapor condensing with carbon dioxide and other combustion compounds is extremely acidic and can eat away at the mortar between bricks or clay liner tiles, eventually causes cracks that can leak dangerous gases into your house. One solution to this problem is to install a flexible stainless steel chimney liner inside your flue. The new liner will physically separate water and other combustion products from the masonry chimney structure, so corrosive effects of water infiltration are stopped immediately. A flexible steel liner offers other advantages besides preventing corrosive water damage. By insulating the inside of the flue, the liner keeps combustion gases hotter as they rise up the chimney, so less condensation of water, soot, and creosote occurs. The round cross section of the chimney liner also lets gases flow easier up the chimney than they do in a square flue. This smoother flow, coupled with higher temperature, can improve the drafting ability of the fireplace, thus making the fire burn cleaner and hotter. Protecting your chimney from water damage from all directions is a good investment.