Water in Chimneys & Fireplaces: Warning Signs & Prevention

Woman repairing a brick chimney with caulk.

Chimneys are a necessary bridge between your home and the outside. Without it, smoke and vapor from your fireplaces or appliances wouldn’t be able to escape, leading to health hazards and other dangers. The most common concern? Moisture. Experts know the risks of water in chimneys or fireplaces, but do you? Read on to learn what to look for and how to prevent water in your chimney.

Signs of Water in Your Chimney

One of the most obvious signs of a leak in your chimney is, of course, seeing water in the fireplace or chimney. However, in many cases, the symptoms of this problem won’t be quite so obvious. If you suspect water in your chimney or fireplace, look for one of these signs:

  • Audible dripping sound, even if you can’t see any water.
  • Water stains or moist sections inside the firebox or chimney
  • Musty odor from (mold or mildew)
  • Cracking in the interior or exterior masonry

You can often identify some of these symptoms more readily after a heavy rain or snow, particularly the musty smell. If you notice cracked or chipped masonry, brick or mortar, it suggests that the water problem may not be recent. That’s one reason that having annual chimney inspections is important!

Potential Damage from Water in Chimneys or Fireplaces

There are plenty of reasons you should be on the lookout for water coming through your chimney or fireplace. In addition to mold or mildew, there are many ways water can damage your home, chimney or fireplace:

  • Rusted or deteriorated damper or firebox assemblies
  • Rusted fireplace accessories or glass doors
  • Stained chimney interior and exterior
  • Cracked flue lining system
  • Weakened hearth support
  • Rotted wood and supports adjacent to the fireplace

And that’s just the beginning! Water in your chimney is a big problem, and that’s why every modern chimney system includes numerous ways to fight against it. However, no option is perfect, and they all require care and frequent inspection.

Common Sources of Water in Chimneys & Fireplaces

Rain Directly Entering the Chimney

When it rains or snows, do you have a noticeable amount of water enter your chimney? Chances are, you don’t have a chimney cap or your chimney cap is damaged. A chimney cap is one of the most important parts of your chimney. It will prevent rain from entering your chimney, which will protect it and your fireplace from damage. Without a chimney cap, you’re left unprotected from animal invaders as well!

Cracked Chimney Crown

One of the most common sources of water in your chimney is a cracked chimney crown. Chimney crowns are slabs of concrete or masonry that seal the chimney at its top. Older homes that use common mortar mix for chimney crowns often only last a few years before cracking. All it takes is one small crack for moisture to begin wearing away and entering your chimney. Because of its position, it tends to be an “out of sight, out of mind” issue. Homeowners won’t recognize that their crown needs repair until they see a leak.

You can repair your chimney crown by applying a crown sealer. Sealants like flexible elastomeric coating are a great option. Not only will they reseal the crack, but they help prevent new cracks from appearing too. If you’re not sure where the crack is, or aren’t into DIY repair, give Doctor Flue a call and we can help identify and fix the problem!

It’s critical to remember that you must use appropriate sealant for anything involving your chimney or fireplace. While it’s important to keep moisture out, brick sealers won’t allow moisture to escape from the inside, which can cause more damage. This is also why it can be a bad idea to paint your chimney. Always use a vapor permeable water-repellent.

Deteriorated Mortar Joints

It’s inevitable that mortar will deteriorate over time. This is due to the constant weathering it experiences, particularly from absorbing moisture. Unfortunately, as the gaps begin to form, they allow the mortar to absorb even more water, which speeds up their deterioration and causes water to seep into your chimney.

You can fill and repair the the external parts of the mortar joints in your chimney’s masonry to help you restore the exterior protection offered by the mortar. This renewal is called repointing – and it’s a great way to restore integrity to your chimney’s brickwork. As an added benefit, it will also improve the look of your chimney – in many cases, making it look brand new!

Damaged Flashing

There is a significant gap between your chimney and the construction around it leading to the roof. Flashing seals this gap and prevents moisture from making its way in. It’s common to “pin” the flashing to the roof with nails, followed by sealing the edges with caulking to waterproof it. Like deteriorating mortar joints, caulking is also susceptible to developing cracks due to weathering or UV exposure.

It’s often easy to spot damaged or failing flashing – look for rust spots or holes. It’s also possible that, when the caulking becomes sufficiently damaged, the flashing itself may lose its seal on an end and require more caulking.

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