How Many Bends can a Chimney Flue have? (Explained!)

Each building is different in one way or another. Therefore, you can’t install a straight chimney in every other house. In fact, some homes don’t have appropriate construction to accommodate a chimney. So, whether or not your chimney flue requires a bend greatly depends on the architecture.

Here’s How Many Bends can a Chimney Flue have:

Generally, a chimney flue can have four bends in total. If you can’t avoid bends, then it should not be more than four bends, which must go along the length of your chimney. Also, a single bend should be at a 45-degree angle from the vertical. However, one 90-degree bend can act as a substitute for two 45-degree bends.

Do you want to learn more about the bends in your chimney? If so, we have answered some of the most-asked questions to help you understand whether you need a chimney or not.

Does a Chimney Flue have to be Straight?

The straighter your chimney, the better it will work, so try to make sure that 80% of your chimney stays vertical. A chimney flue is a passage that runs from the firebox to the top of your roof. This passage is important to allow most of the smoke to escape the chimney rather than collecting in your house.

If your chimney flue has several bends from the bottom to the top, it becomes difficult for the smoke to escape. In this case, smoke may take longer than usual to reach the top of the chimney cap. Or, it may simply start escaping through the firebox, putting your house in danger.

Note that smoke can lead to lung conditions, destroy items in your home, and can be fatal if it accumulates and goes unnoticed. Therefore, experts recommend avoiding bends in the chimney flue. Even if you have to make bends in your chimney flue, take the advice of an expert who can help you understand how much you can afford to bend.

Are Chimney Bends Legal?

If you want to build a chimney in your house, you need to do so according to local building regulations. There are several requirements about bends, chimney construction, and inner liner that you must have to meet. But if you’re wondering whether or not chimney bends are legal, then the simple answer is yes.

Regardless of where you live in the US, you are allowed to install chimney bends. In fact, straight chimneys are pretty rare in the country. Homes with contemporary designs have made it challenging to install a straight chimney. So, if you are struggling with the same problem, then getting a maximum of four bends in your chimney will not cause you any legal trouble.

However, remember to keep other laws in mind. For instance, if your home is built after 1964, it should have a concrete/clay inner liner. Older homes are not subjected to these laws. They should only have a lining if case the chimney is leaking.

How Many Bends Can a Chimney Flue Have?

As we discussed above, a chimney can have a total of four bends – not more than that. But you should opt for bends while considering several factors. Each bend should be at a 45-degree angle. Some factory-made chimney flue models have 90-degree bends that work great for some houses.

Note that the bend in your chimney should not exceed 20% of the total length of your chimney flue. Your chimney is responsible for maintaining a proper inflow of oxygen that helps in combustion. It also helps your chimney maintain the outflow of harmful fumes and gases.

For this reason, if you are planning to add bends to your chimney flue, make sure that the first bend is a few meters above the firebox. This is so that the smoke reaches a certain height it’s forced to change its direction.

Can You Have a 90 Degree Bend in a Chimney?

90-degree bends in chimneys are pretty common, and many factory-made chimney flues come with this. You need to keep the chimney flue 90 degrees from the ground level if you need to bend it.

The 90-degree angle prevents excessive smoke from gathering around the chimney and inside your house. However, if you’re opting for 90-degree bends, you have to reduce the number of bends in your chimney. You can opt for the 90-degree bend as a substitute for two 45-degree bends.

If you try to opt for multiple 90-degree bends, the smoke and fumes will find it hard to leave the fireplace. Aside from federal regulations, you can install bends in your chimney flue after considering local building codes. This applies whether you have a metal or brick chimney.

At What Angles can You Bend Your Chimney?

First thing first, when it comes to bending a chimney flue, an expert recommends keeping it straight. But if you don’t have any choice and you greatly need a chimney in your house, then you can make bends as necessary.

It is best to bend your chimney at an angle of 30 degrees or lower. This provides the smoke an easy way to leave the fireplace. For houses that require bends at higher angles, 45 degrees is as high as you can go, with a limit of up to four bends.

If you have no choice and you must have to increase the angle, then set one bend to 90 degrees and avoid getting further bends. Furthermore, if you have to meet offset requirements, then you can build two slopes of 15 degrees. In short, you can set angles of up to 30 degrees, like 45 degrees and 90 degrees.

Why do Experts recommend to Avoid Bends?

Bends in the chimney flue can obstruct the inflow of oxygen. It also causes problems in the outflow of the byproducts of the fireplace. Having bends in the chimney flue also makes it difficult to clean, as soot can gather at the offset points.

When you have a straight flue, it’s easier for professionals to inspect the chimney for possible problems. If you hire someone to maintain the chimney, they can also complete tasks easily- in less time with less trouble.

In case you didn’t know already, installing a chimney with a bent flue costs you more money than installing a straight one, as this type of chimney requires more expertise. Similarly, repairing and fixing a chimney with bends is more expensive for the same reason.

Bottom Line

While bends in a chimney flue are common in households or commercial properties, it is recommended to avoid them. Bending will not damage your house or cause a fire, but it can cause trouble in the flue’s functioning. The smoke and fumes will take time to leave the fireplace. Therefore, if you set your chimney at improper angles, it may force the smoke to collect inside your house.

Chimneys are important parts of a home, especially if your region is prone to cold, snowy winters. But even so, it’s important to install them in a way that can help you rather than cause more trouble. So, make sure that you consider the basics before installing a chimney in your home. This way, you can prevent problems in the future.