Chimney Flashing
One of the critical steps in building a chimney is to properly install the flashing where the chimney passes through the roof to prevent water leakage. By building code, the chimney must be at least two inches from any wood structure which means there is a two inch gap between the chimney and the roof. That is where the chimney flashing comes into play. It is stalled around the chimney to prevent water from entering the gap and running down the chimney inside the house. On a conventional masonry chimney or brick chimney, lead flashing is used because it is pliable and will not deteriorate. The flashing is inserted between the bricks and then folded down to meet the roof line. In recent years the lead flashing has been replaced by tin, copper and aluminum.
Metal chimneys such as stainless steel chimneys use a metal boot arrangement to close the opening between the chimney and the wood structure. It is usually made of aluminum or galvanized sheet metal. The boot slips over the chimney pipe and is attached to the roof.
If you have water spots on your ceiling near the chimney area or water running down the side of the chimney into the basement the cause is most likely from a chimney flashing leak. Chimney flashing leaks are quite common due to the fact that chimneys are not directly attached to the house structure. All houses settle in the first few years after construction which causes the chimney flashing to pull away from the chimney causing flashing leaks.
There are other reasons for flashing to fail. Flashing made from tin, copper, aluminum and galvanized sheet metal corrodes due to the weather and the continuous expansion and contraction of the metal. Eventually the flashing begins to leak. Lead flashing is nearly impervious to corrosion and will last for decades without leaking. If the flashing is either cemented into the chimney mortar or is sealed to the chimney and the roof by a polyurethane caulk. Over time the caulk dries out and crack allowing water to penetrate underneath the chimney flashing and eventually show up on your ceilings.
When roof shingles are replaced the chimney flashing should be inspected for deterioration. Any deteriorated flashing should be replaced at this time. If it is in good condition replace the sealing caulk. If you are a DIY handyman and do your own roofing repairs you should keep in mind that working on roofs can be a dangerous job. You should wear proper rubber-soled shoes and clothing. Wear a harness that is attached to the roof to prevent falling from the roof. Walk as little as possible on the roofing shingles. Excessive foot traffic can damage the shingles.
If you enjoyed this post, please consider to leave a comment or subscribe to the feed and get future articles delivered to your feed reader.