Chimneys are designed to allow smoke and toxic by-products of combustible materials to safely escape from fireplaces, wood stoves, and furnaces. The earliest versions were simply holes cut through the roofs of thatch structures – while we have certainly come a long way since then, they still perform the same function and are essentially holes in your home (albeit far more sophisticated ones!). 

So, how do chimneys work when it rains? How do they ensure harmful gasses exit while barring water from entering? And, finally, what happens if yours isn’t doing its job? 

How Chimneys Work When It Rains 

A chimney would be little use if you couldn’t use it in inclement weather. Even if the flurries aren’t flying, cold, wet late fall and early spring weather means many of us are firing up our heating systems. When the weather outside is frightful, what keeps the inside delightful? 

Many “actors” play a role in the functioning of the chimney, but the chimney crown and cap are the stars here.  

Chimney Crown: This a large metal, concrete, or stone slab that covers the entire opening and extends about 2 – 2.5 inches over the chimney structure. When rain or snow falls, the crown directs the water onto the roof where it can flow down without damaging the chimney. 

Chimney Cap (also called a rain cap): Think of the cap like an umbrella; placed directly on top of the flue or over the crown, it prevents precipitation and moisture from entering your home. We highly recommend installing a cap that has a wire mesh screen as well; this keeps birds, critters, nesting materials, leaves, and other debris from finding their way down your chimney like Old St. Nick. The cap also keeps embers and sparks in, vastly reducing the risk of a roof fire. 

Some chimney caps are designed to improve draft, which helps pull smoke and noxious byproducts (e.g. carbon monoxide) out of your home, replacing it with cooler air, which pushes more smoke and gas out. This helps enhance safety and gives your fires a better chance at success. 

Water Is the Enemy! 

Keeping water away from and out of your chimney is critical; moisture can cause significant damage to the structure. In addition, you risk weakening the walls and ceiling around your fireplace/stove, damage to the firebox, cracking of the flue, rusting and corrosion, and other problems that can lead to unsafe, and expensive, issues. 

If you do see some water infiltration with your chimney, it might be because: 

  • You do not have a rain cap. These may not be installed as a matter of course but rather as an “optional” add-on. It’s not optional! Invest a small amount for a big return. 
  • You have the wrong rain cap. If the rain cap does not fit optimally, it exposes your flue and fireplace/stove to the elements. This is little better than no cap at all. 
  • Your flashing is not functioning properly. Flashing is a thin metal material installed around the chimney. It diverts water away from the chimney and roof. If it is not installed properly or it has worn down, water is allowed entry – and this can lead to roof, chimney, ceiling, and wall damage. 
  • Your masonry is damaged. If you have a brick and mortar chimney, the components can break down over time. The bricks can spall (i.e. splinter apart) and crack. Not only does this make your chimney look unkempt and shabby, it sets you up for serious problems. 

Chimneys are complex systems, and leaks can be difficult to detect. Often, homeowners do not realize there is a problem until they’re dealing with extensive damage. The best way to prevent expensive headaches – and, most importantly, protect your family, home, and possessions – is to schedule regular chimney inspections and cleanings. While the Brick + Ember team is well-versed in repairing damage, we are committed to helping you avoid this costly step. 

Brick + Ember is committed to ensuring your system works optimally and safely. Get in touch with us to discuss your needs. We are here for you. 

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