Chimney Leak Repair

Chimney leak repairs can be confusing because it is difficult to find where the leak is actually coming from. There are so many different entry points for the water that pinpointing the actual leak can be very difficult. In fact, when there is a leak in a room that is near a chimney, most homeowners don’t consider that their chimney may be the source of the problem.

chimney leak repair

Because the chimney extends above the roofline, it is affected by weather much more so than the rest of your home’s exterior. Is the leak coming from inside the chimney or maybe around the chimney flashing? Sometimes using two people, one person can be up on the roof and use a garden hose to slowly wet down the chimney bricks, starting near the base of the chimney where it enters the roof. The second person can be in the room where the fireplace is located or, better yet, in the attic to watch for water drips. Always work slowly and upward as you search for possible leaks.

Most chimney leaks show themselves when wet spots or wet areas appear on the ceiling near a fireplace. Because these leaks are slow to develop, sometimes a spot of mold will be the first thing you will notice. Not all chimney leaks are seen on the ceiling, sometimes the water will travel all the way down the fireplace or wall to the floor and dampen carpet and carpet cushion, or puddle on a hard flooring surface.

Common Causes of Chimney Leaks

If one of these is not the problem, your leak is probably not coming from your chimney. There is mostly likely some other issue involved.

  1. Rains Entering Straight Down the Chimney: Every chimney should have a rain cover. A properly installed cover will keep not only the rain out, but also birds, animals like squirrels and raccoons, and other debris. Water running down the flue usually becomes a leak only when the flue liner is metal. Installing or replacing a chimney rain cover is one of the easiest and least expensive chimney leak repairs that you can do.
  2. Faulty Flashing: Issues with the flashing causes the majority of chimney leaks. Flashing is thin sheets of tin, aluminum, or other type of impenetrable material, used to create a water resistant barrier around a base of the chimney and other vent openings in the roof. The flashing has to be properly sealed along the bricks of the chimney and the shingles of the roof. Although the flashing will deteriorate over time, a flashing leak is more often a problem of sealant failure. Many products can be used as the sealant; tar, silicone caulking, and roof cement are popular materials. A favorite of many roof installers is Flash Seal. It is also a good idea to apply a small amount of the sealer on top of any nail heads that you may see.
  3. Damaged or Non-Existent Chimney Liners: Because gas fumes are of a very low temperature and carry lots of moisture, having a damaged chimney liner, or no liner at all, will allow the moisture in the fumes to soak the bricks of the chimney. This doesn’t necessarily result in a leak, but it will allow moisture to pass through the brick and into other structural materials such as wood framing and drywall.
  4. Cracks On the Chimney Crown: The crown of a chimney is the concrete at the top of the chimney from which the flue extends. The top is angled to keep water from pooling on it and should extend slightly farther than the brick. As the chimney structure ages, it can flex or shift causing the concrete crown to crack. When this happens, rainwater is able to travel straight through the cracks. When the crack first appears it may be very small. Then as water collecting in these cracks freezes and thaws throughout a winter, the crack widens. You can apply a sealer to the crown as a “band-aid” fix, however, it would to better to remove the crown and replace it with new concrete.
  5. Brick Is NOT A Waterproof Material: Contrary to popular belief, bricks are not waterproof. Because both bricks and mortar contain tiny openings, or passageways, water can and will pass through or even be absorbed by bricks and mortar. A brick sealer can and should be used periodically to reseal the bricks in your chimney, but be careful because any old silicon sealer may cause more issues than it might fix. It is possible to seal water “inside” the bricks causing them to soften and crumble. Today’s leading chimney professionals recommend Chimney Saver because it reduces water penetration and yet it is almost 100% vapor permeable, which means it won’t trap the water vapors released inside the gas fumes when a fire is burning and the chimney is in use. The way this type of “sealer” works is it coats the small passageways without sealing the passageways shut, so that water cannot be absorbed into the brick or mortar.
  6. Cracked or Loose Mortar: As mortar ages, it can become loose or crack and fall out. One common problem that leads to mortar cracks is building settlement. These types of settlement cracks usually follow a stair-step approach. They go straight up a few courses and then crack horizontally. During a wind-driven rain, water can find these loose or missing areas and enter the chimney and then be directed onto a ceiling or it can flow down to the floor. You can fix these areas by applying new mortar into the cracks. Remember to wait at least 24 hours after the repair before using the chimney.

Need Chimney Leak Repair Help?

If you think that you may have an issue requiring chimney leak repair and would like to speak with a pre-qualified chimney repair professional in your area, call 877-960-0491. A local chimney leak repair specialist will answer your call 24 hours and day. They will schedule a time for a free, no-obligation appointment to inspect your chimney for damage and water leaks. 

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Written by Mark Huey.