Can You Use a Fireplace When It’s Raining? (Answered)

Because some nights have been below freezing, we wanted to start up the fireplace, but we were worried about the heavy rains outside. To help answer this we did some research. So, can you use a fireplace when it’s raining?

Fireplaces are designed to be used in most weather conditions, including rain and snow. Most fireplaces have a chimney cap which keeps rain, snow, and animals out of the chimney. Some also have a cowl that blocks wind and sideways rain. Avoid using your fireplace if its masonry has cracks and is leaking.

So, to keep your fireplace and chimney working at their best, it can help to know a little more about how they work in rainy weather conditions. Let’s check out some more details.

What Happens to A Fireplace When It Rains?

Even though rain falls at an angle, it usually can’t enter chimneys or fireplaces due to the chimney cap. For a fireplace to stop working when it’s raining, there would need to be a lot of downward moisture pressure. However, if the chimney doesn’t have any leaks, it will keep moisture out, regardless of the downpour.

However, water damage to a chimney is more common than you might think. To better explain water’s effect on chimneys and fireplaces, it’s helpful to know a bit more about the construction of chimneys.

Chimneys fall into two categories: masonry and stainless steel.

Masonry chimneys are made of bricks, concrete, flue tiles, steel, motor, and cast iron. Stainless steel chimneys are industry-built and the preferred type for modern houses.

Water from either rain or snow can be very unforgiving to masonry chimneys as it erodes the bricks. Over time, water can seep in through the cracks in the bricks. It’s made worse when the water freezes and expands, causing even more cracking within the bricks.

So, it’s not surprising that the majority of chimneys deteriorate during freeze and thaw cycles. Because of this, masonry chimneys in climates with freeze/thaw cycles require ongoing maintenance to fix any cracks that may develop.

Contrary to popular belief, chimneys are a complex feature of houses. Due to this, if your chimney has any issues, they should be addressed by a professional unless you know what you’re doing. Most of the time, if there is a leak from the chimney, it can be difficult to pinpoint the exact cause of it.

A regular chimney inspection will help identify any issues and prevent them from getting worse or unsafe for the household. This is why a yearly chimney inspection is highly recommended.

How Do Chimneys Keep Rain Out?

Fireplaces keep the rain out in 3 ways:

• Chimney Cap
• Chimney Cowl
• Damper (make sure to open when you have a lit fire)

The most important part of a chimney that keeps rain out is the chimney cap. Chimney caps are a cover for the top of the chimney that usually has a slight slant. This slant allows rain to slide away from the chimney.

Chimney caps are inexpensive, especially compared to the cost of repairing a water-damaged chimney.

On the other hand, chimney cowls are best for windy areas and perform better than chimney caps.

The main difference between a chimney cap and a cowl is that cowls block the wind from one side, while still ensuring that smoke gets to escape from the other.

Fireplace dampers also help to prevent rainwater and other elements from getting into the fireplace and chimney. The good news is that you don’t need to climb your roof to access it like a cap and cowl.

Dampers are located at the top of the firebox (see graphic above) and have a lever to open and close them.

Dampers, when closed, will close off the chimney, preventing the elements from getting in (just make sure to open the damper when you’re using your fireplace otherwise you’ll get a house full of smoke!).

Chimney degradation won’t happen in a day or a month. It happens over some months or years until the chimney gives in.

When a chimney, especially a masonry chimney, is exposed to the elements constantly, cracks develop in the brick and concrete and rainwater and ice will expand and contract it constantly.

Leaks in chimneys often go unnoticed until the damage is irreversible. As a homeowner, ensure you’re conducting yearly maintenance and checking for chimney cracks every so often.

Here are some of the signs that may indicate that your chimney is leaking: 

• There is a dripping water sound in the chimney
• You notice condensation or even water inside the firebox 
• There are leaks, moisture, and water stains on the ceilings and walls that surround the chimney
• There is a musky odor every time it rains
• The exterior masonry of the chimney is cracked or there is a spalled interior

Usually, chimneys are fitted with different accessories that ensure moisture doesn’t seep into the fireplace. The accessories include a chimney cowl, chimney cap, and damper.

The caps are usually flat, rectangular pieces made with metal and are placed directly above the top of the chimney. Chimney caps are sometimes referred to as “chimney umbrellas” due to their appearance and how they shield chimneys from the rain. The cap covers the opening while ensuring that smoke can still exit.

The main functions of chimney caps are to prevent water, snow, and animals from settling in the chimney.

How to Keep Rain Out of Your Chimney

When it’s raining, a damper or chimney cap can effectively block out rainwater from seeping through to the fireplace.

Also, regular preventative maintenance, such as annual sweepings and inspections, is vital to keeping rainwater out. This can identify damage early so you can have it repaired before it causes leakage.

One of the best ways of keeping rain from your chimney however is waterproofing your masonry. This involves applying a sealant that keeps rainwater out while ensuring that the masonry retains a semi-porous nature.

The good thing is that such sealants can be applied to chimneys that have already been exposed to water damage to prevent it from getting worse. If after a heavy downpour, your chimney starts leaking, consider calling a professional.

For more information about why chimneys leak, check out this video by Rooftop Chimney Sweeps.

Why Do Fireplaces Smell When It Rains?

Fireplaces smell when it rains due to the moisture mixing with creosote, or tar buildup in the chimney. This can create a musty smell that fills the room or house.

Additionally, the smell can be worse if there’s a leak in the chimney. If your fireplace smells after it rains, consider getting your chimney inspected.

So how do you deal with fireplace smell after a rainstorm?

The best way is to close your damper when you’re not using your fireplace. This should seal any draft your fireplace has and prevent it from being carried through your house.

Also, try cleaning the firebox every so often to get rid of debris and residues that may coat the inside of the fireplace. While cleaning these areas might not get rid of your fireplace’s bad odor, it should at least reduce it.

Sources

• Water & Your Masonry Chimney – CSIA.org