The source of water problems should always be treated as a process of elimination. There are innumerable points of entry for water into a home. Here in Cincinnati we get thousands of calls asking for my service technicians to come out and give their expert opinions on how to best fix leaky chimneys. People will get leaks above their mantle, in their attic, on their ceilings, anywhere! Although any technician who comes out should check the integrity of the brick by looking for loose mortar joints, visible cracks, or other tell tale sign of water entry, he or she should also check the places where surfaces meet. The flashing, the joining of the chimney and the roof, is one such place.
If cracks are obvious in the brick, this may be one point of entry for water into any home. You can check to see if cracks are your issue by waiting for the interior to dry completely and begin spraying your chimney with water from the foundation up, gradually moving to see if, at a certain height on the chimney, moisture begins to appear in the home once more. If you come to diagnose your problem at a particular height on the chimney, you should seal the cracks with a brick sealant, repair any loose mortar joints between the brick, and apply a water repellent to the entire chimney.
Choosing the right water repellent is sometimes half the battle. Be sure that your water repellent will not trap vapors inside the brick, as this would only worsen your problem. Utilizing water repellents, like those manufactured by ChimneySaver, which form a semi permeable membrane over the brick is ideal. Such water repellents will allow vapors that naturally occur in small percentages in the brick to escape will still preventing new precipitation from entering the home.
If the brick on the chimney does not seem to necessarily be the issue, your flashing may be at fault. ChimneySaver has an interesting product called FlashSeal, a flexible flashing sealant with an easy brush-on application, specially formulated to seal your flashing and prevent water entry. The membrane formed by this particular sealant is flexible so that it will not crack or cause damage to the roof or the flashing as the temperature of the roof and flashing increases and decreases. Such temperature changes cause the shingles and the flashing to expand and contract. Sealants must be flexible or else they will cause damage to the shifting particles of the roof.
One gallon of FlashSeal covers approximately 28 sq. ft. You must apply the product in temperatures that are above 45 degrees Fahrenheit, and apply it with a brush. FlashSeal easily and permanently adheres to asphalt shingles, metal flashing, brick, and other chimney and roofing materials. This product is another option in the process of elimination to diagnose exactly where water is penetrating your home.
Remember, the best way to fix leaky chimneys is to make sure the integrity of the chimney and flashing is intact, then apply a breathable water repellent to the brick and mortar joints. If you are trying to fix a leaky fireplace, water is most likely coming in from the chimney crown, brick and mortar or flashing. Check those areas first and you’ll most likely solve any other water leaks coming in and around your chimney or fireplace.