A boiler flue has an important job: carrying waste gases, including carbon monoxide, safely out of your home when your boiler is running.

Whether you need to replace a boiler flue due to a new boiler installation or damage, we have all the boiler flue replacement costs involved.

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What does a boiler flue replacement cost?

The average boiler flue replacement cost (supply & install) is £200 for a straightforward horizontal boiler flue.

However, if your installation is more complex, your costs will start to climb. Let's get into it.

How much does a boiler flue cost?

Most boiler flues in the UK are horizontal. These channel exhaust fumes straight through the external wall on which your boiler is installed.

You can expect to pay around £100 for a basic horizontal flue kit (supply only).

Vertical flue replacement cost

On the other hand, a vertical flue carries fumes from your boiler through the roof instead of your wall.

As such, they tend to be longer and often need extensions to be added to the pipework, leading to higher costs.

As a rough guide, a vertical flue kit could cost anywhere between £100 and £500 (supply only). You'll then need to add on the cost of the installation. That's up next.

Or, for an exact quote, download our free mobile app to connect with central heating engineers near you.

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How much does it cost to install a new boiler flue?

How much a central heating engineer charges to supply and install a new boiler flue depends on the amount of work involved:

Horizontal boiler flue supply & installation cost

A typical horizontal boiler flue costs around £200 to install, including parts.

If the work is being done as part of a new boiler installation, this figure is often included in your overall project price.

Vertical boiler flue supply & installation cost

A vertical flue installation takes more work and labour time.

For a full vertical installation, including supply (around six metres of flue pipe through the roof) and making good the brickwork where the old flue was removed, you're looking at around £550 on average.

However, exactly how much you'll pay depends on the complexity of the installation, if scaffolding is needed, and how far your flue needs to travel. Which brings us to...

How much does a boiler flue extension cost?

If you're moving your boiler somewhere other than an external wall, you'll often need to add an extension pipe so your flue can reach a safe area outside.

Extending your boiler flue in this way typically costs around £75 to £125 per metre.

This includes both supply and installation, as well as the cost of creating a new hole for the flue to exit your home.

Factors affecting the cost of replacing a boiler flue

When estimating the cost of replacing a boiler flue, there are lots of different factors to consider.

Here are the main ones:

• Whether it's a horizontal or vertical flue

• The length of the flue

• The complexity of the installation

• Whether an access tower or scaffolding is required

• Whether other work is being carried out at the same time

If you're having your flue replaced as part of a new boiler installation, the price of a standard horizontal flue will usually be included in your overall cost.

However, if you need a vertical flue and the installation is particularly complex, you may be charged a separate fee.

Boiler flue rules and regulations: What you need to know

Boiler flues have to meet strict clearance rules, covering how close they can be to windows, doors, and neighbouring properties, set out in the Gas Safety (Installation and Use) Regulations.

A Gas Safe registered engineer will know the exact distances for your flue type and make sure your installation is signed off correctly.

If you rent out a property, flue clearance is also checked as part of a gas safety certificate inspection.

Is a boiler flue replacement worth the cost?

Your boiler flue is an essential part of your boiler. In fact, it's just as important as the boiler itself, as it keeps your home safe from poisonous gases like carbon monoxide.

If you're considering a boiler flue replacement, it's likely to boil down to one of three reasons:

1. Boiler repair

If everything goes as planned, your flue should last as long as your boiler.

But if your flue is faulty, it will need to be repaired or replaced quickly for the safety of everyone in your home.

Replacing the boiler flue is one of the most common boiler repair costs.

2. Boiler replacement

Similarly, you'll need to replace your boiler flue if you get a new boiler. If you're planning a full central heating installation rather than a like-for-like swap, your flue will be replaced as part of that wider job.

This will normally be included in your overall price, so it won't be a figure you have to worry about.

3. Moving a boiler

Lastly, moving your boiler to a new position in your home will require a new boiler flue.

Most boilers are located on an external wall. But if you want to move yours to an internal wall to save space, this is where your costs can quickly climb, especially if the cost of a new gas installation is also needed to reroute pipework.

It may not be strictly necessary, but if it increases the usable space in your home, it'll often be worth the cost!

Boiler flue replacement cost: job estimator tool

Use our job estimator below to get a rough idea of costs before you start requesting quotes. If you're also pricing up a full boiler swap, Checkatrade's boiler installation cost calculator is worth checking at the same time.

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Or for an exact quote, speak to a Gas-Safe engineer near you.

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Boiler flue replacement cost checklist

Before you contact a tradesperson, here's what to check.

Boiler flue replacement cost checklist

• Check whether your flue is horizontal (through the wall) or vertical (through the roof)

• Work out the rough length your new flue needs to travel from your boiler to the outside

• Confirm whether you're replacing a faulty flue, fitting a new boiler, or moving your boiler to a new spot

• Check access needs, like scaffolding or a tower, if the flue runs up an external wall

• Confirm the engineer is Gas Safe registered (Remember: only a Gas Safe registered engineer can legally fit or replace a boiler flue)

• Ask whether the work is being quoted separately or bundled into a wider boiler installation

How to find a checked Gas Safe engineer

Use our quick and easy request a quote feature and we'll get experienced local gas engineers to contact you directly. To get accurate quotes, be as detailed as you can:

• Whether your flue is horizontal or vertical

• Roughly how far your flue needs to travel from the boiler

• Whether it's a repair, replacement, or part of a new boiler installation

• Any access issues, like scaffolding needs

Once you've compared a few quotes, take a look at more heating advice below.

Looking into other maintenance jobs for your boiler or central heating system? From finding Gas Safe engineers for boiler servicing or power flushing, we're here to help.

Why use Checkatrade to find Gas Safe engineers near you?

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Request a quote, search in the Checkatrade app, or enter your postcode to find local Gas Safe engineers near you.

Boiler flue replacement cost FAQs

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