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Bay Window Replacement Cost

Are you thinking of having a bay window replaced? In this article, we’ll discuss the cost of installing a bay window based on size and type. We’ll also look at how long it takes to install a bay window, whether you can fit one DIY, and what the various types of bay windows are, among other relevant topics.

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Introduction to Bay Window Replacement

This article will prove useful if you plan to have a bay window installed in the near future or even at some point down the line.

Cream bay window

Bay windows are window spaces that project out from the walls of a property. This creates a bay in the internal space.

The job we are focused on in this article looks at replacing this type of window. Given that bay windows tend to date back to the 19th century, it is not uncommon for these windows to be replaced as they age and deteriorate.

How Much Does It Cost to Replace a Bay Window?

The average cost of replacing a three-section bay window with a uPVC frame is £1075 to £1350. If there are four sections, expect to be billed for about £1500 to £2000 or £2725 to £3050 if there are five sections/panels.

If you’d like to have a new bay window installed with a painted timber frame, should it have three panels, a replacement would cost about £1900 to £2400.

The cost will reach £2225 to £2700 if there are four sections or £2625 to £3150 if there are five sections. The exact same price estimates apply for bay windows with an aluminium frame as in the latter case.

Labour Cost

Let’s start breaking down the overall cost. The labour cost of replacing a three panelled bay window with a uPVC frame is £375 to £450 with the price rising to £500 to £600 should a uPVC framed window consist of four sections, or £625 to £750 if it has five sections.

As for a bay window with a painted timber frame, labour costs will be around £500 to £600 if it is a three panelled window, with labour prices being roughly £625 to £750 for either a four or five panelled timber frame window.

The same price estimates apply for an aluminium framed bay window as it would for a bay window with a painted timber frame.

On average, you’d pay about £250 to £300 per day in labour costs to hire two window fitters for the job. In some cases, only one or even three window fitters will perform the work, but it is generally two.

Supply Costs

Now, looking at supply costs, you can expect to pay about £700 to £900 for the materials for a three-panel bay window with a uPVC frame.

For such a window with four panels, it would cost around £1000 to £1400 or £2100 to £2300 if it were to be a five panelled window.

When it comes to a bay window with a painted timber frame, supply costs will be roughly £1400 to £1800 if it has three sections, £1600 to £2000 if it consists of four sections or £2000 to £2400 if it contains five sections.

As for a bay window with an aluminium frame, the same price estimates apply as shown for a painted timber-framed bay window.

Cost Factors

The cost of replacing bay windows will depend primarily on the size/type of window(s). However, the window dimensions, number of windows being replaced, ease of access, state of the installation area, and property location are all important in shaping the total cost.

Man installing bay window

Where you live is significant given that labour costs vary depending on where specifically you reside in the UK.

For example, labour prices tend to be highest in the southeast of England (and London especially) but lower than the UK average in regions such as the north of England, Scotland, and Northern Ireland.

Total Cost of Replacing a Bay Window

Frame Type Number of Sections/Panels Labour Cost Supply Costs Total Cost
uPVC 3 £375 to £450 £700 to £900 £1075 to £1350
4 £500 to £600 £1000 to £1400 £1500 to £2000
5 £625 to £750 £2100 to £2300 £2725 to £3050
Painted Timber 3 £500 to £600 £1400 to £1800 £1900 to £2400
4 £625 to £750 £1600 to £2000 £2225 to £2750
5 £625 to £750 £2000 to £2400 £2625 to £3150
Aluminium 3 £500 to £600 £1400 to £1800 £1900 to £2400
4 £625 to £750 £1600 to £2000 £2225 to £2750
5 £625 to £750 £2000 to £2400 £2625 to £3150

Types of Bay Windows

In this section, we’ll take a look at a variety of bay window styles. This will give you an idea as to the pros & cons of each choice, helping you to determine which type of bay window is the best fit for you and your home.

Bow Bay Window

As the name implies, a bow bay window is shaped like a bow. It has a curved, smooth shape similar to that of a traditional hunters bow.

Bow bay window

Bow windows provide a curved effect internally and in the exterior of the property. These windows generally allow more light in than other bay window types. Bow windows generally come with four or five panels.


✔ Aesthetic

✔ Tend to let more light in


✖ Less often available with three sections if you’d prefer

Box Bay Window

This type of window features a rectangular box appearance instead of a curved or rounded shape. Box bay windows create an area within a room that is thus shaped like a box. The formality, straight lines and neat corners offered by box bay windows can be appealing to some homeowners.


✔ Creates a box-shape

✔ Formal appearance

✔ Preferable for some homeowners


✖ May be boring for some homeowners

Oriel Bay Window

This type of bay window tends to appear on the upper section of a home rather than on the ground floor. Oriel bay windows are usually held up with corbels or brackets. These windows have risen in popularity among homeowners who have sought to enhance the view from the second floor or higher floor rooms in a property.


✔ Well-suited to higher floors of a property

✔ Ideal for enhancing upper floor views


✖ Not well-suited to ground floor rooms

Circle Bay Window

These windows have a less traditional view than most bay windows. Circle bay windows come with a smoother and more circular aesthetic than most bay windows, making them a more modern solution. They are most often used in bedroom suites and sizeable living rooms.

Circle bay window


✔ More modern look

✔ A smooth and circular design

✔ Well-suited to large living rooms and bedroom suites


✖ Less traditional appearance

What Does Changing Bay Windows Involve?

In this section, we’ll discuss the steps involved in replacing bay windows.

1. Hiring Window Fitters

Before any work can begin, it’s important that you find a well-suited contractor/company for the job.

In the process of finding the right individual or company for the job, you should acquire at least three quotes and references. This will help you make a smart choice in choosing from several viable options.

After you’ve hired a contractor/company, they will pop by at a later date to measure the window(s), such that they can order the correct window sizes.

You may already know what style of bay window you’d like, but you should consider consulting the window fitter in case they have their own bay window replacement ideas worth considering.

Though you could order the window materials by yourself, it is generally best practice to leave it to a professional contractor/company due to their experience with this type of work

2. Removing the Old Windows

On the day of installing the new bay windows, first and foremost, the window fitter(s) will need to remove the current bay windows.

Removing bay windows must be done in such a way as to minimise the risk of physical damage to the walls or any other fixtures.

More than likely, the contractors will wear masks and safety goggles, given how dusty this sort of work can be. The windows and their frames are removed during this step.

3. Installing the Frames

The space should be measured once more to make certain that no chiselling is required to ensure that the new windows will fit perfectly.

Chiselling will take place if necessary. If not, it’s straight on to installing the new frames to the inner wall space.

Flashing tape will be used to stop moisture and air from entering these spaces. The window frames must be installed level and aligned before the windows can be added.

4. Adding the New Windows

The new bay windows will be fitted to the wall and fixed in place within the frames with a variety of fixings such as overhead support cables.

Replacing a bay window

These will be used to connect the windows to the roof before being covered with a decorative roof cab at a later point.

5. Insulation and Finalisation

Insulation is important to prevent unnecessary heat loss. Windows that lack insulation are poor for energy efficiency and will result in higher heating bills.

The last touches include adding sealant around the window frame edges and making sure that the windows are secure and working as planned.

The old windows and their frames, along with any other waste, will now be disposed of and the area made clean and fresh for your use.

6. Additional Work

As for additional costs, there are a variety of extra jobs you may wish to pay for following the replacement of bay windows.

For example, to have a new front door installed would cost anywhere from £500 to £2500. To have the exterior of your property painted would set you back somewhere in the range of £400 to £1500.

More related to installing a bay window in particular, you’d like to pay somewhere between £60 and £150 to have a single curtain handrail installed or £130 to £270 for a double handrail.

As for the actual curtains, they may cost less than £50 for budget products, but more often, you can expect to pay several hundred pounds.

DIY Bay Window Replacement

You can replace a bay window DIY, but it is advisable to only do so if you’re sure of what is involved and are aware of any necessary safety precautions (i.e. wearing a mask and glasses).

Building regulations do apply for window replacement jobs, and more information can be found via Planning Portal.

It should be noted that the regulations listed on Planning Portal apply to England and Wales; therefore the rules may differ in England and Wales.

DIY bay window replacement

The same is true of planning permission. You may need to have a professional sign off after replacing bay windows, but if you have any uncertainties, you should contact your local council.

As with any DIY work there are a variety of risks and hazards involved. Firstly, after removing the existing bay window there will be a large open space in front of you and this would lead to a dangerous drop if you are replacing bay windows above the ground floor.

Further, you should proceed with caution if using tools/equipment such as chisels and you should be careful when lifting heavy materials.

There is also a danger of an incorrect installation since installing bay windows can be a tricky job. All in all, you should leave the work to professionals unless you are confident of your skills and knowledge in this area.

Potential Problems and Pitfalls

As with any trades work, there are a variety of issues and downfalls worth taking into account. Firstly, replacing bay windows can be expensive.

Beyond that, the work can be disruptive for several days and there is always a chance that you will come to regret the new bay window instalment, especially if you cannot find the ideal type of bay window for you.

Should your applications for planning permission or building regulations approval be rejected, you’ll need to apply again with the appropriate changes made to your application(s).

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Sam J

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