Can a chimney flue be angled?

Author: Velda Okuneva I  |  Last update: Saturday, June 7, 2025

If a flue must be angled or offset, the angle can be no more than 30 degrees from vertical. In an offset situation, the joints of the flue liners must be neat and flush forming a smooth interior surface free of excess mortar, ledges and other obstructions.

Do chimney flues have to be straight?

The entire route from fire to chimney terminal needs to be smooth, straight and vertical wherever possible.

Can you vent a fireplace at an angle?

To vent the fireplace, a pair of rigid flues nestled inside one another—called a coaxial unit, since they both share an axis—is installed in sections ranging from 4" to 48" in length, with 90°- and 45° angled elbows that allow for flexibility with placement.

Does a flue pipe have to go straight up?

First of all, the chimney pipes should be positioned so that they are as vertical as possible. It is important to go through walls or partitions with 45° bends. In addition, horizontal runs and 90° bends should be avoided at all costs, as they cause flue gases and clog the flues.

What are the rules for flue bends?

If bends are necessary there must be no more than four in the length of the chimney. The angle of the bend should be no greater than 45° from the vertical, with the exception that 90° factory made bends or tees may be treated as being equal to two 45° bends.

Fitting a stove and re-lining a chimney flue using steel flexible liner

Can a fireplace flue be angled?

The answer is “yes”! It's done every day and is perfectly safe to do so, provided codes are followed and equipment is properly maintained. NFPA 211 (US regulations) states that chimneys can be offset 15° or 30° while CSA B365 (Canadian regulations) states it can be offset at a 30° to 45° angle.

Can you have a bend in a chimney flue?

The most effective form of flue system is a vertical, internal chimney however, you do have up to 4 bends or turns allowed within the system should you need to negotiate around an obstacle along the way in the form of 45° Elbows (never 90°) and a Roof Support should be used on the rafters as a final form of support.

Can a flue go sideways?

Typically made from metal or plastic, the flue is directly connected to the combustion chamber of the boiler - running vertically or horizontally out of your home.

Does a vent pipe have to be vertical?

Vent pipes must be installed so they stay dry. This means that they should emerge from the top of the drainpipe, either straight vertically or at no less than a 45-degree angle from horizontal, so that water cannot back up into them.

Can you push a flue liner up a chimney?

The liner can be slid up or down the chimney a little at any stage in the stove fitting process to aid fitting the stove.

Can a vent pipe have angles?

Vents serve your plumbing as well as appliances such as your appliance dryer. Can a vent stack have bends in it? Vent stacks can only have 45-degree angled piping to route horizontal pipe and connect to vertical pipe.

Can a chimney vent sideways?

The short answer to whether you can vent a wood-burning fireplace horizontally is, generally, no. Wood-burning fireplaces require proper venting systems that effectively draw smoke and combustion gases out of the home.

Can a chimney flue run horizontally?

A wood burning flue cannot run horizontally, only the stove pipe and the snout of a Tee is allowed to.

Does a flue need to be vertical?

Most flues are fitted horizontally, although it may be appropriate for flues to be placed vertically on some properties. If the boiler is not fitted to an external wall, for example, a vertical may be used to channel waste gases through and out of the roof space.

Can a balanced flue go up a chimney?

A balanced flue pipe can only work with a balanced flue fire - it cannot be used with a traditional or flueless gas fire. Similarly, if you have a balanced flue fire, you can't use it with a traditional chimney.

Does a vent pipe need to be straight?

A plumbing vent does not necessarily have to go straight up. While it is common for vents to run vertically and extend through the roof, there are alternative venting methods available, including: Horizontal vents: These vents run parallel to the building's floor and connect to a vertical vent or vent stack.

Can a vent pipe have bends?

In conclusion, while plumbing vents are traditionally designed as straight pipes, bends are permissible under certain conditions. Proper planning, adherence to local building codes, and maintaining the required slope are crucial factors when considering bends in plumbing vents.

Can a sewer line have a 45 degree angle?

Re: Are 45 degree fittings allowed in horizontal drain pipe? To answer your question, yes they are allowed, but only in a horizontal configuration. You cannot use them to change elevation.

Does a chimney flue have to go straight up?

The ideal flue pipe assembly is one that rises straight up from the appliance flue collar and directly into the chimney with no elbows.

Can a flue have a 90 degree angle?

Yes, 90-degree bends can be fitted with our condensing boilers if the correct allowance is made on the maximum flue length.

Can you bend a chimney flue?

usually Stove installations will use a 45 degree angle and you should not exceed 4 bends in the overall flue system. The offset measurement should not exceed 20 % of the total chimney length. For example a standard flue height is 4500mm or 4.5 metres therefore the offset should not exceed 900mm.

Does chimney pipe have to be straight?

depends on how often you want to clean it. It is easier to clean your chimney if there are no bends. I have seen many chimney fires in my area and they are typically because the chimney has not been cleaned or maintained. If straight up is an option I would go for that as a practical safety precaution.

Can you have a horizontal flue?

A boiler flue, most common in the UK, comes outside of a house drilling into an external wall is called a horizontal flue. This flue comes out of a house from the boiler to the outer wall straightly.

How high should a chimney be for a wood burning stove?

Building Regulations recommend a minimum flue height of 4.5m however the chimney must be high enough to allow for enough draught to clear the exhaust gases.

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